Title of Invention	"AN IMPROVED EFFLUENT TREATMENT PLANT USEFUL FOR THE TREATMENT OF TANNERY WASTEWATER TO OBTAIN NON-POLLUTING WATER AND A PROCESS THEREOF"
Abstract	The present invention reports an improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, which comprises an improved conventional effluent treatment plant (CETP), characterized in that the said CETP being provided in combination with an electrochemical reactor selectively at stages the receiving sump stage, post anaerobic lagoon treatment stage, post secondary clarification stage and pre final discharge stage and the said electrochemical reactor consisting of anode which is a plate of conductive metals having electrocatalytic coating such as metallic or ceramic and cathode of stainless steel of similar geometry as that of the anode and the distance of anode and cathode being kept in the range of 2- 4 cm and current density of the electrochemical reactor being kept in the range of 2-4A./dm2.

Title of Invention

"AN IMPROVED EFFLUENT TREATMENT PLANT USEFUL FOR THE TREATMENT OF TANNERY WASTEWATER TO OBTAIN NON-POLLUTING WATER AND A PROCESS THEREOF"

Abstract

The present invention reports an improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, which comprises an improved conventional effluent treatment plant (CETP), characterized in that the said CETP being provided in combination with an electrochemical reactor selectively at stages the receiving sump stage, post anaerobic lagoon treatment stage, post secondary clarification stage and pre final discharge stage and the said electrochemical reactor consisting of anode which is a plate of conductive metals having electrocatalytic coating such as metallic or ceramic and cathode of stainless steel of similar geometry as that of the anode and the distance of anode and cathode being kept in the range of 2- 4 cm and current density of the electrochemical reactor being kept in the range of 2-4A./dm2.

Full Text	The present invention relates to an improved effluent treatment plant for the treatment of tannery wastewater to obtain non-polluting water and a process thereof. The present invention particularly relates to an improved conventional effluent treatment plant (CETP) being provided with an electrochemical reactor at stages such as the receiving sump, post anaerobic lagoon treatment, post secondary clarification and pre-final discharge. The improved effluent treatment plant of the present invention allows electrochemical treatment of tannery wastewaters, particularly for removal of ammonia (NH4+), chemical oxygen demand (COD) and total Kjeldhal nitrogen (TKN), using electrodes comprising of an electrocatalytic metallic or ceramic coating obtained by electrodeposition and/or thermal decomposition techniques. The invention is useful for both final polishing of tannery wastewater as well as an alternative to a step of biological denitrification of tannery wastewater. Tannery wastewater usually contains ammonia (50-1500 mg/L) and organic substances (COD : 200-2500 mg/L) in a very high concentration together with chloride (2500-4500 mg/L) at different stages of treatment. Adequate treatment of tannery wastewater is of very great importance prior to its discharge onto inland surface waters. Tannery wastewater is at present treated through physicochemical and biological treatment units and the effluent thus treated is let into river. The schematic drawing of a Common Effluent Treatment Plant (CETP) is shown in Fig.1 of the drawings accompanying this specification. The plant consists of: (1) Screen Chamber (2) Receiving Sump (3) Rotary Screen (4) Equalization Basin (5) Flash Mixer I (6) Baffle Channel (7) Primary Clarifier (8) Anaerobic Lagoon (9) Pre-aeration Tank (10) Aeration Tank (11) Secondary Clarifier (12) Flash Mixer II (13) Flocculator (14) Tube Settler (15) Sludge Drying Beds (16) Sludge Thickener (17) Centrifuge A/B - Alum/Lime C/D- DAP/Polyelectrolyte + Mixer * Floating Aerator * Fixed Aerator --Sludge Line The major steps of treatment, as detailed in figure 1 of the drawings, include equalization, chemical addition and flocculation, clarification, anaerobic lagooning, aeration and settling before treated wastewater is discharged. The performance of anaerobic and aerobic units in Fig.1 often fluctuates due to its dependence on ambient temperature that varies in the range 20-45°C in different seasons prevailing in India. This in turn affects the quality of treated effluent, often affecting the parameters such as ammonia, COD, BOD and TKN which remain higher than the corresponding discharge standards. The removal of nitrogenous compounds from industrial wastewater by biological nitrification is particularly sensitive to temperature variation. The discharge of insufficiently treated tannery wastewater into any surface water body exerts long term changes in the quality of surface water itself. For example, the high organic content together with nitrogenous compounds interfere with dissolved oxygen content of surface water, alkalinity and sulphide affect aquatic life, suspended solids make water turbid, the colouring substances present in treated wastewater may alter appearance, taste and odour of surface water body. Research continues in an effort to develop improved processes for the treatment of different types of wastewater and there have been efforts to apply electrochemical reaction procedures to tannery wastewater treatment. For example, research conducted by us has demonstrated that many pollutants including ammonium and organic impurities can be removed effectively by direct or indirect electrochemical oxidation. Reference may be made to L. Szpyrkowicz and F-Z. Grandi, Toxicol. Environ. Chem. 44, 183, 1994; L. Szpyrkowicz and J. Naumczyk and F. Zilio- Grandi, Water Res. 49, 517, 1995; Somasekhar K. M., Kaul S. N. and Rao N. N." Electrochemical Treatment for Tannery Wastewater" M. Tech Dissertation, 1998; N. N. Rao, K. M. Somasekhar, S. N. Kaul and L. Szpyrkowicz, J. Chem. Technol. Biotechnol. 76,1124-1131, 2001. Using graphite anode and steel cathode, Sczpyrkowicz et al could fully eliminate ammonia with 19% current efficiency. The energy consumed for the removal of 1 Kg of NH3 from the final effluent was equal to 132 kWh. On the other hand, electroooxidation of tannery wastewater using Ti/PtOa, Ti/MnC>2, and Ti/PbC>2 results in substantial removal of ammonia and COD. While ammonia removal efficiency ranged from 65-95%, the current efficiency for COD removal is found to range between 15 and 70%. Further more than 70-80% of color can also be removed. Reference may be made to V. Smith de surce, A.P. Watkinson, Can. J. Chem. Eng., 59, 1981, p. 529; oxidation of phenol by electrochemical route wherein phenol is readily oxidized at a Pb02 anode, but complete TOC removals are not achieved. Reference may be made to C. Pulgarin, N Adler, P. Pertnger ad C. Comminellis, Wat. Res., 28(4), pp. 887-893, 1994, wherein the most toxic xenobiotic such as 1,4-benzoquninone is oxidized at Ti/lr02 and Ti/Sn02 anodes and total oxidation was achieved only with Ti/Sn02 anode. This oxidation with Ti/lr02 lead to buildup of aliphatic acids that are easily biodegraded subsequently. This could be regarded as a pretreatment method for converting the originally recalcitrant waste into biodegradable waste. Reference may be made to O.J. Murphy, G.D. Hitchens, L. Kaba and Charles E. Verosko; Water. Res. 26, pp. 443-451,1992, wherein a dozen organic compounds (aliphatic or aromatic acids/alcohols) in low ionic conductivity water are electrochemically oxidized using a solid electrolyte electrode assembly. This paper describes the construction and testing of a single cell electrochemical reactor that uses Nafion®117-proton exchange membrane (PEM) as solid polymer electrolyte in place of a conventional liquid electrolyte. The anode and cathode, made up of Pt-lr(10%) mesh, were hot pressed on either side of PEM and ohmic contact was made through Ti plates as current collectors. The above assembly has demonstrated the ability to remove organic constituents from initial concentration of 50-100 ppm to less than 500 ppb TOC. Reference may be made to U.B. Ogutvern and S. Koparal, J. Environ. Sci. Health, A 29(1), pp. 1-16,1994, wherein coloured sewage wastewater containing 50-60 mg/L NaCI is treated using bipolar packed bed reactor and complete colour removal achieved. When applied to a local textile effluent, the system responded with 82% color removal efficiency. The decolourization in this case is done by mainly active chlorine derived in the electrolyzer from sodium chloride. Reference may be made to S.H. Lin and Chi. F. Peng, Water Res. 28, 277, 1994 and Water Res. 30, 587, 1996, wherein the electroxidation of textile wastewater which had a 694 mg/L COD concentration is carried out with reduction efficiency of 40%. When integrated to physico-chemical process such as coagulation; the total residual COD after electrochemical treatment was found 236 mg/L. The electrochemical reactor used in these studies had eight cast iron anode plates (19.5cm x 12cm) and eight stainless steel cathode plates of the same size. Reference may be made to Li-Choung Chiang, J-E Chang, T.C. Wen, Water Res. 29(2), pp. 671-678, 1995, wherein treatment of a landfill leachate having a low BOD/COD ratio is conducted by means of electrochemical oxidation process. The landfill leachate collected from a sanitary landfill site of five-year burial age is treated in an electrochemical reactor consisting of Ti/PbO2, Ti/RuO2. Ti02 and Ti/SnO2-PdO-RuO2 anodes and a steel cathode. Prior to electrolysis, the landfill leachate is made sufficiently saline by adding NaCI, which acted as precursor for In-situ generation of Cl2 and hypochlorite. Using Ti/SnO2-PdO-RuO2 anode at 15A/dm2 current density, about 92% of the COD in the landfill leachate (initial COD * 4100-5000 mg/L) were removed. Simultaneously, all the NH4+ (about 2600 mg/L) was removed completely from the leachate. These authors have attributed the removal of COD and NH4+ to the indirect oxidation effect of CI2/OCI" produced during electrolysis. In yet another study by Chiang Li. C; Chang, Juu-E; Wen, Ten-C; Hazard Waste Hazard Mater., Vol. 12 (No. 1), 1995, pp. 71-82, biologically treated landfill leachate was subjected to electrochemical oxidation and over 90% COD and NH4+ removals is reported. The BOD/COD ratio of the landfill leachate is also improved from 0.05 to 0.71 suggesting that even the refractory chloroorganics were also destroyed during electrooxidation process. Electrochemical methods are sometimes used to remove or decompose chemical impurities in water. For example, cathodic reduction is used to remove heavy metal ions including copper, nickel, and silver (A. T. Kuhn, pp. 98-130 in J. O'M. Bockris, Ed., Electrochemistry for a cleaner environment, Plenum Press New York, 1971). Anodic oxidation may be used to destroy cyanide and phenols (A. T. Kuhn, J. Appl. Chem. Biotechnol. 21, 29-33, 1971), ammonia (L. Marincic and F. B. Leitz. J. Appl. Electrochem. 8, 333-345, 1978), organic dyes (M. S. E. Abdo and R. S. AI-Ameeri, J. Environ,. Sci. Health, A22, 27-45, 1987). All of these applications involve very specific anodic reactions involving very specific substrates that occur at moderate anodic potentials below the potential required for generating hydroxyl. Only partial oxidation of the target substrate is achieved. Undesirable byproducts may be formed; for example, electrolytic oxidation of phenol may produce some amount of chlorophenol. An electrochemical method involving the generation of NO radicals in a medium containing nitric acid has been reported (R. N. Gedye, Y. N. Sadana, A. C. E. Edmonds and M. L. Langlois, J. Appl. Electrochem. 17, 731-736, 1987). The free radicals produced react with dissolved organic compounds and destroy them. The reaction requires a high concentration of nitric acid and the lectrolyte is very corrosive. It is therefore practically limited to destroying organic compounds dissolved in strong acid solutions. Hydroxyl free radical is a very powerful, nonspecific oxidizing species which attacks most organic molecules as well as oxidizable inorganic molecules and ions (G. V. Buxton, C. L. Greenstock, W. P. Helman and A. B. Ross, J. Phys. Chem. Ref. Data, 17, 513-759, 1988). Hydroxyl radicals may be produced by irradiation with Ultraviolet light of particles of titanum dioxide dispersed in water (C. Kormann, D. W. Bahnemann and M. R. Hoffmann, Environ. Sci. Technol, 25, 494-500, 1991) or by reaction of hydrogen peroxide with iron salts dissolved in mildly acidic solution, called Fenton's reaction. Electrochemical production of hydroxyl radicals utilizing electrodes with various semiconducting surface compositions has been described (Chez, US Patent 4,676,878). Bianchi (US Patents 3,948,751 and 4,003,817) described electrodes wherein a titanium metal base is covered with an oxide coating which contains titanium dioxide, a large portion of a platinum group metal, and in some examples also niobium and tantalum. In this prior art, much higher anode potentials were required to produce hydroxyl radicals. In Weres et al (US Patent 5,364,508) have demonstrated that hydroxyl free radicals can be produced and organic substances dissolved in water can be oxidized at Ea Inventions related to the electrochemical treatment of effluent water to remove suspended solids, dissolved particles and bacterial contamination exist in literature. Reference may be made to Lin et al (US Patent 6,083,377) where nitrogenous compounds such as nitrate and ammonium etc., are treated by electrochemical transformations of the contaminant to nitrogen gas. Another reference may be made to Clarke et al (US patent 5,861,090) who disclosed a method for electrochemically remediating soil, clay or other media contaminated with organic pollutants using Fenton's reagent. The proposed technique is a method of electrochemical deployment of Fenton's reagent that can be applied in-situ for the treatment of soils and clays. A method and apparatus for decontamination and purification of liquid mediums from toxic organic substances and other impurities is available (US Patent 6,296,744). This apparatus produces sterilizing solution, disinfectant, decontaminant, bleach, antiseptic detergent with the aim of disinfecting the liquid medium. An electrochemical cell comprising of nitric acid electrolyte containing silver ions as an electrochemically regenerable primary oxidizing species for decomposing organic waste matter is also known (Coulin et al, EP 0 297 738). Reference may be made to Mac Dougall etal (US patent 5, 662, 789) who invented a process for electrochemically collecting certain organic compounds from aqueous solutions in an immobilized and concentrated manner conducive to subsequent destruction. The method involves electrochemical formation of coupling products that are water insoluble and form deposits or films on working electrode surface. A process for galvanocoagulation through electrochemical formation of hydoxides of heavy metals as coagulants for removing through adsorption has been described by Tamarkin et al (US Patent 5, 658,450). Pressurized air, when passed through the cell, caused flotation and enhanced impurity removal. A process for mediated electrochemical oxidation of organic wastes without electrode separators is described by Farmer et al (US Patent 5,516,972). The metal salt mediators in sulphuric acid electrolyte in the presence of electrodes lead to efficient destruction of organic contaminants. Herbst et al (US Patent 6,241,861) described a water treatment tank for treating wastewater using electrochemical treatment process. The electrochemical process removes both suspended and dissolved solids in the wastewater and heavy contaminants settle to the bottom while lighter than water contaminants are removed by vacuum from the top of the tank. In an invention related to the field of electrochemical wastewater treatment, Ritter eat al (US Patent 6,214,182) disclosed a device for treatment using electroflocculation. An electrochemical water treatment device for producing hydroxyl free radicals and decomposing by oxidation chemical substances dissolved in water was described by Weres et al (US Patent 5,439,577). It utilizes a novel electrode, which is capable of operation at sufficiently positive anodic potential to produce hydroxyl radicals. In prior art, procedures applied to electrochemical treatment of different wastewaters exemplified that the electrochemical methods are applicable to wastewater treatment. Many inventions relate to development of electrodes, devices and methods for electrochemically producing oxidants, disinfectants, metal hydroxides etc., for removing or decomposing the specific chemical and microbial pollutants. No prior art recited above is able to completely oxidize organic substrates, nor oxidize in a non-specific manner a vide variety of chemical substances dissolved in water. However, the potential of a electrochemical method for treating actual wastewater such as tannery wastewater comprising of several nonspecific pollutants has not been explored; particularly, the electrochemical treatment of tannery wastewater from different stages of conventional treatment. The main object of the present invention is to provide an improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, which obviates the drawbacks of the hitherto known equipment. Another object of the present invention is to provide a process for the treatment of effluent such as tannery wastewater to obtain non-polluting water, which obviates the drawbacks of the hitherto known processes. Yet another object of the present invention is to provide an improved conventional effluent treatment plant (CETP) being provided with an electrochemical reactor at stages such as the receiving sump, post anaerobic lagoon treatment, post secondary clarification and pre-final discharge. Still another object of the present invention is to provide an electrochemical process for the treatment of tannery wastewater to obtain non-polluting water, which is an improvement of existing treatment for this wastewater. The present invention seeks to provide the following technical result: an improvement in the conventional scheme of treatment of tannery wastewater, eliminate some of the treatment steps therein by way of inserting the proposed electrochemical reactor in place of one or more unit operations in conventional scheme and yet achieve desired treatment efficiency. The ability of electrochemical process to effect universal treatment for the variety of contaminants found in the wastewater is unique. This is exemplified by treating tannery wastewater from different stages of conventional treatment scheme shown in Fig.1 of the drawings. Advantageously the invention results in a compact treatment scheme with equal or better treatment efficiency, as insertion of electrochemical reactor would make some of the conventional unit operations down the treatment scheme in Fig.1 unnecessary. In another aspect of the Present invention, it provides an improved wastewater treatment process for tannery wastewater that obviates the problems due to temperature dependence of biological nitrification processes. A typical batch electrochemical reactor of the present invention is shown in Fig. 2 of the drawings accompanying this specification. The electrochemical reactor comprises of a set of parallel electrodes (1,2) immersed in an electrolyte, such as tannery wastewater, and joined to a regulated Direct Current power supply. The anode (1) surface comprises of electrocatalytic metal, metalloxide or mixed oxide ( ceramic ) coating obtained as per the reported procedures in literature. A stainless sheet of similar geometry and area of anode was used as a cathode (2). The distance between anode and cathode can be fixed between 2-4 cm, but in the present case, a distance of 4 cm was found suitable. The electrolyte in the reactor is subjected to agitation through a magnetic needle (3) and magnetic stirring device placed below the reactor. The agitation can also be achieved by employing overheard stirrer. The electrochemical reactor sets in a forced chemical change through the electrolyte owing to the potential difference between anodes and cathodes. The reaction zones are frequently restricted to the surface of electrodes at electrode/electrolyte interfaces. The prepared electrodes were useful for electrochemical elimination of pollutants from tannery wastewater. Accordingly, the present invention provides an improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, which comprises an improved conventional effluent treatment plant (CETP), such as herein been described, characterized in that the said CETP being provided in combination with an electrochemical reactor selectively at stages the receiving sump stage, post anaerobic lagoon treatment stage, post secondary clarification stage and pre final discharge stage and the said electrochemical reactor consisting of anode which is a plate of conductive metals having electrocatalytic coating such as metallic or ceramic and cathode of stainless steel of similar geometry as that of the anode and the distance of anode and cathode being kept in the range of 2- 4 cm and current density of the electrochemical reactor being kept in the range of 2-4A./dm . In an embodiment of the present invention, wherein the electrochemical reactor essentially consists of an anode which is a plate of conductive metal, such as titanium, having electro catalytic coatings such as metallic or ceramic and cathode such as stainless steel of similar geometry as that of the anode. In another embodiment of the present invention, wherein the electrochemical reactor anode having electrocatlytic metallic coating is selected from one or a combination of two metals from Group VIII metals, particularly platinum and iridium. In yet another embodiment of the present invention, wherein the electrochemical reactor anode having electrocatalytic ceramic coating is selected from coatings of oxides or sub oxides of Rh, Pd, Pb and Ti. In still another embodiment of the present invention, wherein the electrochemical reactor anode is selected from anode containing Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) an dTi/PbO2. In still yet another embodiment of the present invention, wherein the said CETP being provided at the receiving sump stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2. In a further embodiment of the present invention, wherein the preferred anode is either Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) for the treatment of raw tannery waste water at the receiving sump stage. In another embodiment of the present invention, wherein the said CETP being provided at the post anaerobic lagoon treatment stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%);Ti/RhOx(50%)/Ti02(50%);Ti/PdO(70%)/Co3O4(30%). In yet another embodiment of the present invention, wherein the preferred anode is Ti/PdO(70%)/Co3O4(30%) at the post anaerobic lagoon treatment stage. In another embodiment of the present invention, wherein the said CETP being provided at the post secondary clarification stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co304(30%) and Ti/Pb02. In still another embodiment of the present invention, wherein the preferred anode is selected from Ti/Pt(70%)/lr(30%), Ti/RhOx(50%)/TiO2(50%) at the post secondary clarification stage. In still yet another embodiment of the present invention, wherein the said CETP being provided at the pre-final discharge stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2. In a further embodiment of the present invention, wherein the preferred anode is Ti/PdO(70%)/Co304(30%) at the pre-final discharge stage. Accordingly, the present invention provides a process for the treatment of effluent to obtain non-polluting water, which comprises treating effluent in the improved effluent treatment plant as herein described, enabling simultaneous removal of ammonium (NH/), Total Kjeldhal Nitrogen (TKN) and Chemical Oxygen Demand (COD). In an embodiment of the present invention wherein a process for the treatment of tannery waste water to obtain non-polluting water, comprises treating the effluent in the improved effluent treatment plant as herein described. In another embodiment of the present invention , wherein the electrochemical reactor current density is in the range of 2 - 4 A/dm2. In the present invention there is provided an improved effluent treatment plant wherein an electrochemical treatment process is provided whereby tannery wastewater is treated using anodes comprising of known electrocatalytic metallic or ceramic coating obtained by electrodeposition/thermal decomposition techniques. A voltage is applied between the anode and cathode and galvanostatic condition was obtained. The applied voltage is a function of conductivity of the tannery wastewater and in each case constant current as high as 2-4A/dm2 was attainable. Due to passing of current in the electrolyte, its temperature is raised to a maximum of 45-50°C. At the anode, there is discharge of chloride ions native to tannery wastewater with the formation of chlorine. Simultaneously electrolysis of water with the formation oxygen also occurs at anode. Hydroxyl radicals may also be produced under the conditions applied above. Chlorine or its derivative hypochlorous acid as well as oxygen based radicals formed at anode react with pollutants such as ammonia, organic compounds including nitrogeneous compounds present in tannery wastewater. This results in reduction of ammonium, COD/TOC concentrations. At the cathode, metal, alkali and alkaline earth metal ions are discharged as their hydroxide precipitates and hydrogen is evolved, resulting in the increase of agitation. This resulted in flotation and scum formation that mainly contributed to colour removal from tannery wastewater. The originally unclear tannery wastewater due to presence of suspended solids became clear in due course of electrochemical process as heavy particles settled to bottom while lighter ones were lifted to electrolyte's top in the form of scum. During electrochemical treatment of tannery wastewater, two main reaction pathways viz., direct electro-oxidation and indirect electro-oxidation, particularly in reference to ammonium removal may occur. The direct reaction expressed as in Equation 1, (Equation 1 Removed) usually proceeds well over platinum anode, titanium electrodes covered with electrodeposited noble metals such as Pt, Ru, and Rh and their iridium alloys. The indirect anodic oxidation relies on the in-situ electrochemical production of oxidizing agents, particularly chlorine and hypochlorite. Indirect oxidation can be applied for wastewater containing high concentration of chloride ions. In this case, the free chlorine produced at anode reacts with ammonium ions to give nitrogen gas as a final product that escapes into air readily, as shown in Equation 2 below: (Equation 2 Removed) Since tannery wastewater contains 2500 - 4500 mg/L chlorides, the indirect oxidation route may be profitably used for ammonia removal. In an embodiment of the present invention the following different electrodes were prepared as per the reported procedures and used as anodes. The different anodes are: 1. Ti/Pt(70%)/lr(30%) 2. Ti/RhOx(50%)/Ti02(50%) 3. Ti/PdO(70%)/Co3O4(30%) 4. Ti/PbO2 The electrodes were obtained by electrodeposition or thermal decomposition in a way similar to the previously reported procedures (R.T.Atanasoski, B. Z. Nikolic, M. M. Jaksic and A. R. Despic, J Appl. Electrochem. 5, 155-158, 1975; US Appl. 549194, 1966; US 3 632 498,1978; US 3 711 385, 1973; Brit. Pat. 1 399 576,1973). The support metal substrate is of suitable geometry (plates) and made of a conductive metal, namely titanium. The metallic electrocatalytic coatings were obtained on to Ti substrate by electrodeposition from appropriate bath solutions containing precursor metal salts, generally metal halides. The electrocatalytic ceramic coating may be directly applied onto the support metal substrate by thermal decomposition of precursor metal salt solutions/dispersions. The latter was obtained in repeated layers. The anodes in the present invention contain the electrocatalytic metallic coatings of one or a combination of two metals from Group VIII metals, particularly platinum and iridium in a pre-selected weight percent. The electrocatalytic ceramic-coated anodes constitute coatings of oxides or suboxides of Rh, Pd, Pb and Ti. The following examples are given by way of illustration of the improved effluent treatment plant and process to obtain non-polluting water in greater detail and should not be construed to limit the scope of the present invention. The removal efficiencies, detention times required to achieve the effluent standards, kinetic constants for ammonia and COD removal and energy consumption and energy requirements are reported for all different electrodes under different current conditions and for different types of tannery wastewater. All experiments were conducted separately with each of the above-referred electrodes using four types of tannery wastewater collected at different stages of treatment, varying the conditions of electrochemical treatment. The different types of tannery wastewater examined were: • Raw tannery wastewater (after stage 2 in Fig.1) • After anaerobic lagoon treatment (after stage 8 in Fig.1) • After secondary clarification (after stage 11 in Fig.1) • Final effluent (after stage 14 in Fig. 1). It is therefore, to be intended that the invention is not limited to the specific examples reported herein below. Furthermore, it should be understood that the effluent treatment plant and process, of the present invention, described herein might be extended to other types of suitable wastewaters also, in principle, particularly if the effluent contains ammonia and chloride together in significant quantities. It should be also borne in mind that other metal and ceramic deposits on the supporting metal substrate may also result in useful anodes in the effluent treatment plant and process of the present invention. EXAMPLE 1 In this example, the electrochemical treatment of raw wastewater (after stage 2 in Fig.1) was carried out in the batch reactor using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co304(30%) and Ti/PbO2 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm-2. Throughout the duration of experiment, the reactor contents (electrolyte) were stirred continuously with the help of a magnetic stirrer. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may be required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOC), ammonium (NH4+), Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals. The efficiency of removal of ammonia, TKN and COD from raw tannery wastewater is reflected through Fig.3 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (2) as a primary treatment unit for treating raw tannery wastewater from sump (1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2A/dm2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment are seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+, COD, TKN and S2- decreased substantially upon electrochemical pretreatment. This anode was replaced by the other anodes Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The first order kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 1-4. Table-1: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from raw wastewater (Table Removed) Table-2: Detention times required for meeting effluent standards for TKN and COD using different types of electrodes in raw wastewater (Table Removed) Table-3: Energy consumption (EC) using different types of electrodes for the treatment of raw wastewater (Table Removed) Table-4: Energy requirement (ER) using different types of electrodes for the treatment of raw wastewater (Table Removed) It can be seen that the rate constants for ammonium removal (k[NH4+]) using Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%) and Ti/PdO(70%)/Co304(30%) increased 2.6, 12.3 and 3.26 times when current is doubled from 2A/dm2 to 4A/dm2. The rate constant at Ti/RhOx/Ti02 is found more sensitive to current change. The k[NH4+] at Ti/Pb02 is higher than at other anodes, while COD removal using this anode is very insignificant. Further, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-2) decreased drastically as current is doubled. For example, Ti/RhOx(50%)/TiO2(50%) that required 25h at 2A/dm2, needed only about 2h at 4A/dm2. A similar trend was found with respect to COD removal also. The energy consumption (Table-3, EC, kWh/Kg TKN or COD) for COD removal increased drastically with increase in current density, while that for TKN removal decreased. Thus EC for TKN removal at Ti/RhOx(50%)/Ti02(50%) at 4A/dm2 is 4 times less compared to 833 kWh/Kg TKN at 2A/dm2. The anode performance as per EC for TKN and COD removal may be written in the order: Ti/PbO2 > Ti/Pt(70%)/lr(30%) ~Ti/PdO(70%)/Co304(30%) > Ti/RhOx(50%)/TiO2(50%), and Ti/RhOx(50%)/Ti02(50%)> Ti/PdO(70%)/Co304(30%)>Ti/Pt(70%)/lr(30%). The energy requirement (Table-4, kwh/m3 ) for the removal of TKN from 1m3 raw tannery wastewater followed the order Ti/PbO2>Ti/Pt(70%)/lr(30%) ~Ti/PdO(70%)/Co304(30%)>Ti/RhOx(50%)/Ti02(50%). Both Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) showed lower energy requirement at 4A/dm2. Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 3 of the drawings, advantageously causes treatment of raw tannery wastewater thereby making operational units down the scheme in Fig.1 unnecessary. However, due to higher initial pollution load in raw tannery wastewater the energy consumption, energy requirement and detention times are high for electrochemical treatment of this waste. EXAMPLE 2 In this example, the electrochemical treatment of anaerobically treated tannery wastewater (after stage 8 in Fig. 1) was carried out in the batch reactor using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm-2. Throughout the duration of batch experiment, the anaerobically treated tannery wastewater in the reactor was stirred continuously with the help of a magnetic stirrer provided below the reactor. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOC), ammonium (NH4+). Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals. The efficiency of removal of ammonia, TKN and COD from anaerobically treated tannery wastewater is reflected through Fig.4 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (8) for treating anaerobically treated tannery wastewater (after stage 8 in Fig. 1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2Adm"2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment can be seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+, COD, TKN and S2-decreased substantially upon electrochemical pretreatment. This anode was replaced by the other anodes Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co304(30%) and Ti/Pb02 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 5-8. Table-5: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from wastewater after anaerobic lagoon treatment (Table Removed) Table-6: Detention times required for meeting effluent standards for TKN and COD using different types electrodes in waste water after anaerobic lagoon treatment (Table Removed) Table-7: Energy consumption (EC) using different types of electrodes for the treatment of wastewater after anaerobic lagoon treatment (Table Removed) Table-8: Energy requirement (ER) using different types of electrodes for the treatment of wastewater after anaerobic lagoon treatment (Table Removed) It can be seen that the rate constants for ammonium removal (k[NH4+j) using Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) increased 2.9 and 8.75 times when current is doubled from 2A/dm2 to 4A/dm2. The k[NH4+]) at Ti/PdO/Co304 is the highest. The rate constant at Ti/RhOx/Ti02 is found more sensitive to changes in current. The k[coo] at Ti/Pb02 is 0.001. However, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-6) decreased drastically as current is doubled. For example, Ti/RhOx(50%)/TiO2(50%) that required 8h at 2A/dm2, needed only about 3.35h at 4A/dm2 for TKN removal. Similarly, Ti/Pt(70%)/lr(30%) that required 4.3h at 2A/dm2, needed 1.5h at 4A/dm2. A similar trend was found with respect to COD removal also. The energy consumption (Table-3, EC, kWh/Kg TKN or COD) for COD removal remained somewhat invariant with increase in current density, while that for TKN removal decreased. The electrochemical reactor comprising Ti/PdO/Co304 consumed lowest energy, i.e 98kWh/KgTKN. Thus EC for TKN removal at Ti/RhOx(50%)/Ti02(50%) at 4A/dm2 is 3 times less compared to 1131 kWh/Kg TKN at 2A/dm2. The anode performance as per EC for TKN and COD removal may be written in the order: Ti/PdO(70%)/Co304(30%) > Ti/Pt(70%)/lr(30%) > Ti/Pb02 > Ti/RhOx(50%)/Ti02(50%) and Ti/Pt(70%)/lr(30%) > Ti/RhOx(50%)/Ti02(50%) > Ti/Pb02. The energy requirement (Table-8, kwh/m3) for the removal of TKN from 1m3 anaerobically treated tannery wastewater followed the order Ti/PdO(70%)/Co3O4(30%) > Ti/Pt(70%)/lr(30%) > Ti/Pb02 > Ti/RhOx(50%)/TiO2(50%). Both anodes viz., Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) showed lower energy requirement for COD removal at 4A/dm2. Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 4 of the drawings, advantageously causes treatment of anaerobically treated tannery wastewater thereby making operational units down the scheme in Fig.1 unnecessary. It may be seen in terms of higher rate constant, lower detention time, lower energy consumption and lower energy requirement, the Ti/PdO(70%)/Co304(30%) is a preferred anode for the treatment of anaerobically treated tannery wastewater. EXAMPLE 3 In this example, the electrochemical treatment of tannery wastewater after secondary clarification (after stage 11, Fig. 1) was carried out in the batch reactor using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm-2. Throughout the duration of batch experiment, the tannery wastewater after secondary clarification (after stage 11, Fig. 1) in the electrochemical reactor was stirred continuously with the help of a magnetic stirrer provided below the reactor. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOG), ammonium (NH4+), Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals. The efficiency of removal of ammonia, TKN and COD from anaerobically treated tannery wastewater is reflected through Fig.5 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (12) for treating tannery wastewater after secondary clarification (after stage 11, Fig. 1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2Adm-2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment can be seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+ , COD, TKN and S2" decreased substantially upon electrochemical pretreatment and comply with the corresponding discharge standards. This anode was replaced by the other anodes Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 9-12. Table-9: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from wastewater after secondary clarification (Table Removed) Table-10: Detention times required for meeting effluent standards for TKN and COD using different types of electrodes in wastewater after secondary clarification (Table Removed) Table-11: Energy consumption (EC) using different types of electrodes for the treatment of wastewater after secondary clarification (Table Removed) Table-12: Energy requirement (ER) using different types of electrodes for the treatment of wastewater after secondary clarification (Table Removed) The rate constants for ammonium removal (k[NH4+]) followed the order: Ti/Pt(70%)/lr(30%) > Ti/RhOx(50%)/TiO2(50%) > Ti/Pb02 > Ti/PdO/Co3O4 The k[NH4+) at Ti/PdO/Co304 anode is 13 times more when current is doubled from 2A/dm2 to 4A/dm2. The k[NH4+]) at Ti/Pt(70%)/lr(30%) is the highest. The rate constant at Ti/PdO/Co3O4 is found more sensitive to changes in current. The k[coD] at Ti/Pb02 is 0.004. However, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-10) decreased as current is doubled. A similar trend was found with respect to COD removal also. Due to low strength nature of tannery effluent from secondary clarifier, very low detention times as low as a few minutes were adequate for removal of TKN. In case of COD removal, except to Ti/RhOx(50%)/TiO2(50%), all other anodes still require longer detention periods. Thus, Ti/RhOx(50%)/Ti02(50%) requires only 16 min for bringing down COD from secondary clarifier effluent. The energy consumption (Table-11, EC, kWh/Kg TKN or COD) for COD removal decreased with increase in current density, while that for TKN removal remained invariant with Ti/Pt(70%)/lr(30%). The electrochemical reactor comprising Ti/Pt(70%)/lr(30%) consumed lowest energy, i.e 40 kWh/KgTKN at 2A/dm2 and 34 kWh/KgCOD at 4A/dm2. The energy requirement (Table-12, kwh/m3 ) for the removal of TKN from 1m3 tannery effluent from secondary clarifier followed the order > Ti/Pt(70%)/lr(30%) > Ti/RhOx(50%)/Ti02(50%) > Ti/Pb02 > Ti/PdO(70%)/Co304(30%). The anode, Ti/Pt(70%)/lr(30%) showed lower energy requirement for COD removal at 4A/dm2 while Ti/RhOx(50%)/TiO2(50%) showed lower energy requirement for COD as well as TKN removal at 2A/dm2. Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 5 of the drawings, advantageously causes treatment of tannery effluent from secondary clarifier thereby making operational units down the scheme in Fig.1 unnecessary. It may be seen in terms of higher rate constant, lower detention time, lower energy consumption and lower energy requirement, the Ti/Pt(70%)/lr(30%) is a preferred anode for the treatment of tannery effluent from secondary clarifier. However, Ti/RhOx(50%)/TiO2(50%) anode may also be used advantageously for the treatment of tannery effluent from secondary clarifier. EXAMPLE 4 In this example, the electrochemical treatment of tannery wastewater (final effluent after stage 14 in Fig. 1) was carried out in the batch reactor using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm"2. Throughout the duration of batch experiment, the final tannery effluent after tube settler (after stage 14, Fig. 1) in the electrochemical reactor was stirred continuously with the help of a magnetic stirrer provided below the reactor. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOC), ammonium (NH4+), Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals. The efficiency of removal of ammonia, TKN and COD from final tannery effluent is reflected through Fig.6 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (15) for treating final tannery effluent after tube settling (after stage 14, Fig. 1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2Adm-2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment can be seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+, COD, TKN and S2- decreased substantially upon electrochemical pretreatment and comply with the corresponding discharge standards. Particularly the COD and TKN concentrations are further reduced to below standards. This anode was replaced by the other anodes Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 13-16. Table-13: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from final effluent (Table Removed) Table-14: Detention times required for meeting effluent standards for TKN and COD using different types of electrodes in final effluent (Table Removed) Table-15: Energy consumption using different types of electrodes for the treatment of final effluent (Table Removed) Table-16: Energy requirement using different types of electrodes for the treatment of final effluent (Table Removed) The rate constants for ammonium removal (k[NH4+]) followed the order: Ti/PdO/Co304 > Ti/Pt(70%)/lr(30%) > Ti/PbO2 > Ti/RhOx(50%)/TiO2(50%). The k[NH4+)at Ti/Pt(70%)/lr(30%) anode is 3 times more when current is doubled from 2A/dm2 to 4A/dm2. The k[NH4+]) at Ti/RhOx(50%)/Ti02(50%) is the lowest and is insensitive to changes in current. The k[CoD] at Ti/PbO2 is 0.065. However, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-14) did not show decrease when current is doubled. But, the detention times decreased with respect to COD removal at higher current. Due to low strength nature of tannery final effluent very low detention times as low as a few minutes to half an hour were adequate for removal of TKN and COD. The energy consumption (Table-15, EC, kWh/Kg TKN or COD) for TKN removal decreased with increase in current density, while that for COD removal with Ti/Pt (70%)/lr(30%) increased. The electrochemical reactor comprising Ti/PdO/Co304 consumed lowest energy, i.e 12 kWh/KgTKN at 2 &4A/dm2. The energy requirement (Table-16, kwh/m3) for the removal of TKN from 1m3 final effluent followed the order Ti/RhOx(50%)/Ti02(50%) > Ti/Pb02 > Ti/Pt(70%)/lr(30%) > Ti/PdO(70%)/Co304(30%). The anode, Ti/PdO(70%)/Co304(30%) showed lower energy requirement for both TKN & COD removal at 2A/dm2 as well as 4A/dm2. Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 6 of the drawings, advantageously causes treatment of final effluent thereby making operational units down the scheme in Fig.1 unnecessary. It may be seen in terms of higher rate constant, lower detention time, lower energy consumption and lower energy requirement, the Ti/PdO(70%)/Co304(30%) is a preferred anode for the treatment of final effluent. The performance of any anode in the present invention is a critical function of applied current density. Their choice should depend on the parameter of interest for meeting to discharge standard, lower detention time, lower energy consumption and lower energy requirement for removing the intended parameter. For example, we have seen that effective TKN removal necessitates application of higher current, while COD removal would require lower current with lower energy consumption for all types of tannery wastewater examined in the present invention. The main advantages of the present invention are : 1. Considerably reduced time period for satisfactory elimination of ammonia from tannery wastewater compared to the conventional biological processes. 2. Simplification, compactness and ease of operation accrued to the design of tannery effluent treatment plants (ETP). 3. Allows simultaneous removal of ammonium (NH4+), Total Kjeldhal Nitrogen (TKN) and Chemical Oxygen Demand (COD). 4. Allows simultaneous removal of several chemical impurities from tannery wastewater. 5. The invention is useful for both final polishing of tannery wastewater as well as an alternative to a step of biological denitrification of tannery wastewater. We Claim: 1. An improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water which comprises an improved conventional effluent treatment plant (CETP), such as herein been described, characterized in that the said CETP being provided in combination with an electrochemical reactor selectively at stages the receiving sump stage, post anaerobic lagoon treatment stage, post secondary clarification stage and pre final discharge stage and the said electrochemical reactor consisting of anode which is a plate of conductive metals having electrocatalytic coating such as metallic or ceramic and cathode of stainless steel of similar geometry as that of the anode and the distance of anode and cathode being kept in the range of 2- 4 cm and current density of the electrochemical reactor being kept in the range of 2-4A./dm2 . 2. An improved effluent treatment plant as claimed in claims 1, wherein the electrochemical reactor essentially consists of an anode which is a plate of conductive metal, such as titanium having electrocatalytic coating such as metallic or ceramic and cathode stainless steel of similar geometry as that of the anode. 3. An improved effluent treatment plant as claimed in claim 1-2, wherein the electrochemical reactor anode having electrocatalytic metallic coating is selected from one or a combination of two metals from Group VIII metals, particularly platinum and iridium. 4. An improved effluent treatment plant as claimed in claim 1-2, wherein the electrochemical reactor anode having electrocatalytic ceramic coating is selected from coatings of oxides or sub oxides of Rh, Pd, Pb and Ti. 5. An improved effluent treatment plant as claimed in claim 1-4, wherein the electrochemical reactor anode is selected from anode containing Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2 (50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2. 6. An improved effluent treatment plant as claimed in claim 1-5, wherein the said CETP being provided at the receiving sump stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/ TiO2 (50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2. 7. An improved effluent treatment plant as claimed in claim 6, wherein the preferred anode is either Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/TiO2 (50%). 8. An improved effluent treatment plant as claimed in claim 1-7, wherein the said CETP being provided at the post anaerobic lagoon treatment stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%);Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%). 9. An improved effluent treatment plant as claimed in claim 8, wherein the preferred anode is Ti/PdO(70%)/Co3O4(30%). 10. An improved effluent treatment plant as claimed in claim 1-9, wherein the said CETP being provided at the post secondary clarification stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%).and Ti/PbO2. 11. An improved effluent treatment plant as claimed in claim 10, wherein the preferred anode is selected from Ti/Pt(70%)/lr(30%); Ti/RhOx(50%) TiO2 (50%). 12. An improved effluent treatment plant as claimed in claim 1-11, wherein the said CETP being provided at the pre-final discharge stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%) / TiO2 (50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2. 13. An improved effluent treatment plant as claimed in claim 12, wherein the preferred anode is Ti/Pt(70%)/ Co3O4(30%) . 14. A process for the treatment of tannery waste water to obtain non-polluting water, which comprises treating effluent in the improved effluent treatment plant as claimed in claim 1-13, enabling in the improved effluent treatment plant as claimed in claim 1-13, enabling simultaneous removal of ammonium (NH4+), total Kjeldhal nitrogen (TKN) and Chemical Oxygen Demand (COD). 15. A process for the treatment of tannery waste water to obtain non-polluting water, which comprises treating the effluent in the improved effluent treatment plant as claimed in claim 1-13. 16. A process as claimed in claim 14-15, wherein the electrochemical reactor current density is in the range of 2 - 4 A/dm2. 17. An improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, substantially as herein described with reference to the examples and drawings accompanying this specification. 18. A process for the treatment of tannery waste water to obtain non-polluting water, substantially as herein described with reference to the examples and drawings accompanying this speciation.

Full Text

The present invention relates to an improved effluent treatment plant for the treatment of tannery wastewater to obtain non-polluting water and a process thereof.
The present invention particularly relates to an improved conventional effluent treatment plant (CETP) being provided with an electrochemical reactor at stages such as the receiving sump, post anaerobic lagoon treatment, post secondary clarification and pre-final discharge. The improved effluent treatment plant of the present invention allows electrochemical treatment of tannery wastewaters, particularly for removal of ammonia (NH4+), chemical oxygen demand (COD) and total Kjeldhal nitrogen (TKN), using electrodes comprising of an electrocatalytic metallic or ceramic coating obtained by electrodeposition and/or thermal decomposition techniques. The invention is useful for both final polishing of tannery wastewater as well as an alternative to a step of biological denitrification of tannery wastewater.
Tannery wastewater usually contains ammonia (50-1500 mg/L) and organic substances (COD : 200-2500 mg/L) in a very high concentration together with chloride (2500-4500 mg/L) at different stages of treatment. Adequate treatment of tannery wastewater is of very great importance prior to its discharge onto inland surface waters. Tannery wastewater is at present treated through physicochemical and biological treatment units and the effluent thus treated is let into river. The schematic drawing of a Common Effluent Treatment Plant (CETP) is shown in Fig.1 of the drawings accompanying this specification.

The plant consists of:
(1) Screen Chamber
(2) Receiving Sump
(3) Rotary Screen
(4) Equalization Basin
(5) Flash Mixer I
(6) Baffle Channel
(7) Primary Clarifier
(8) Anaerobic Lagoon
(9) Pre-aeration Tank
(10) Aeration Tank
(11) Secondary Clarifier
(12) Flash Mixer II
(13) Flocculator
(14) Tube Settler
(15) Sludge Drying Beds
(16) Sludge Thickener
(17) Centrifuge
A/B - Alum/Lime
C/D- DAP/Polyelectrolyte
+ Mixer
* Floating Aerator * Fixed Aerator
--Sludge Line

The major steps of treatment, as detailed in figure 1 of the drawings, include equalization, chemical addition and flocculation, clarification, anaerobic lagooning, aeration and settling before treated wastewater is discharged.
The performance of anaerobic and aerobic units in Fig.1 often fluctuates due to its dependence on ambient temperature that varies in the range 20-45°C in different seasons prevailing in India. This in turn affects the quality of treated effluent, often affecting the parameters such as ammonia, COD, BOD and TKN which remain higher than the corresponding discharge standards. The removal of nitrogenous compounds from industrial wastewater by biological nitrification is particularly sensitive to temperature variation.
The discharge of insufficiently treated tannery wastewater into any surface water body exerts long term changes in the quality of surface water itself. For example, the high organic content together with nitrogenous compounds interfere with dissolved oxygen content of surface water, alkalinity and sulphide affect aquatic life, suspended solids make water turbid, the colouring substances present in treated wastewater may alter appearance, taste and odour of surface water body.
Research continues in an effort to develop improved processes for the treatment of different types of wastewater and there have been efforts to apply electrochemical reaction procedures to tannery wastewater treatment. For example, research conducted by us has demonstrated that many pollutants including ammonium and organic impurities can be removed effectively by direct or indirect electrochemical oxidation. Reference may be made to L. Szpyrkowicz

and F-Z. Grandi, Toxicol. Environ. Chem. 44, 183, 1994; L. Szpyrkowicz and J. Naumczyk and F. Zilio- Grandi, Water Res. 49, 517, 1995; Somasekhar K. M., Kaul S. N. and Rao N. N." Electrochemical Treatment for Tannery Wastewater" M. Tech Dissertation, 1998; N. N. Rao, K. M. Somasekhar, S. N. Kaul and L. Szpyrkowicz, J. Chem. Technol. Biotechnol. 76,1124-1131, 2001. Using graphite anode and steel cathode, Sczpyrkowicz et al could fully eliminate ammonia with 19% current efficiency. The energy consumed for the removal of 1 Kg of NH3 from the final effluent was equal to 132 kWh. On the other hand, electroooxidation of tannery wastewater using Ti/PtOa, Ti/MnC>2, and Ti/PbC>2 results in substantial removal of ammonia and COD. While ammonia removal efficiency ranged from 65-95%, the current efficiency for COD removal is found to range between 15 and 70%. Further more than 70-80% of color can also be removed.
Reference may be made to V. Smith de surce, A.P. Watkinson, Can. J. Chem. Eng., 59, 1981, p. 529; oxidation of phenol by electrochemical route wherein phenol is readily oxidized at a Pb02 anode, but complete TOC removals are not achieved.
Reference may be made to C. Pulgarin, N Adler, P. Pertnger ad C. Comminellis, Wat. Res., 28(4), pp. 887-893, 1994, wherein the most toxic xenobiotic such as 1,4-benzoquninone is oxidized at Ti/lr02 and Ti/Sn02 anodes and total oxidation was achieved only with Ti/Sn02 anode. This oxidation with Ti/lr02 lead to buildup of aliphatic acids that are easily biodegraded

subsequently. This could be regarded as a pretreatment method for converting the originally recalcitrant waste into biodegradable waste.
Reference may be made to O.J. Murphy, G.D. Hitchens, L. Kaba and Charles E. Verosko; Water. Res. 26, pp. 443-451,1992, wherein a dozen organic compounds (aliphatic or aromatic acids/alcohols) in low ionic conductivity water are electrochemically oxidized using a solid electrolyte electrode assembly. This paper describes the construction and testing of a single cell electrochemical reactor that uses Nafion®117-proton exchange membrane (PEM) as solid polymer electrolyte in place of a conventional liquid electrolyte. The anode and cathode, made up of Pt-lr(10%) mesh, were hot pressed on either side of PEM and ohmic contact was made through Ti plates as current collectors. The above assembly has demonstrated the ability to remove organic constituents from initial concentration of 50-100 ppm to less than 500 ppb TOC.
Reference may be made to U.B. Ogutvern and S. Koparal, J. Environ. Sci. Health, A 29(1), pp. 1-16,1994, wherein coloured sewage wastewater containing 50-60 mg/L NaCI is treated using bipolar packed bed reactor and complete colour removal achieved. When applied to a local textile effluent, the system responded with 82% color removal efficiency. The decolourization in this case is done by mainly active chlorine derived in the electrolyzer from sodium chloride.
Reference may be made to S.H. Lin and Chi. F. Peng, Water Res. 28, 277, 1994 and Water Res. 30, 587, 1996, wherein the electroxidation of textile wastewater which had a 694 mg/L COD concentration is carried out with reduction efficiency of 40%. When integrated to physico-chemical process such

as coagulation; the total residual COD after electrochemical treatment was found 236 mg/L. The electrochemical reactor used in these studies had eight cast iron anode plates (19.5cm x 12cm) and eight stainless steel cathode plates of the same size.
Reference may be made to Li-Choung Chiang, J-E Chang, T.C. Wen, Water Res. 29(2), pp. 671-678, 1995, wherein treatment of a landfill leachate having a low BOD/COD ratio is conducted by means of electrochemical oxidation process. The landfill leachate collected from a sanitary landfill site of five-year burial age is treated in an electrochemical reactor consisting of Ti/PbO2, Ti/RuO2. Ti02 and Ti/SnO2-PdO-RuO2 anodes and a steel cathode. Prior to electrolysis, the landfill leachate is made sufficiently saline by adding NaCI, which acted as precursor for In-situ generation of Cl2 and hypochlorite. Using Ti/SnO2-PdO-RuO2 anode at 15A/dm2 current density, about 92% of the COD in the landfill leachate (initial COD * 4100-5000 mg/L) were removed. Simultaneously, all the NH4+ (about 2600 mg/L) was removed completely from the leachate. These authors have attributed the removal of COD and NH4+ to the indirect oxidation effect of CI2/OCI" produced during electrolysis. In yet another study by Chiang Li. C; Chang, Juu-E; Wen, Ten-C; Hazard Waste Hazard Mater., Vol. 12 (No. 1), 1995, pp. 71-82, biologically treated landfill leachate was subjected to electrochemical oxidation and over 90% COD and NH4+ removals is reported. The BOD/COD ratio of the landfill leachate is also improved from 0.05 to 0.71 suggesting that even the refractory chloroorganics were also destroyed during electrooxidation process.

Electrochemical methods are sometimes used to remove or decompose chemical impurities in water. For example, cathodic reduction is used to remove heavy metal ions including copper, nickel, and silver (A. T. Kuhn, pp. 98-130 in J. O'M. Bockris, Ed., Electrochemistry for a cleaner environment, Plenum Press New York, 1971). Anodic oxidation may be used to destroy cyanide and phenols (A. T. Kuhn, J. Appl. Chem. Biotechnol. 21, 29-33, 1971), ammonia (L. Marincic and F. B. Leitz. J. Appl. Electrochem. 8, 333-345, 1978), organic dyes (M. S. E. Abdo and R. S. AI-Ameeri, J. Environ,. Sci. Health, A22, 27-45, 1987). All of these applications involve very specific anodic reactions involving very specific substrates that occur at moderate anodic potentials below the potential required for generating hydroxyl. Only partial oxidation of the target substrate is achieved. Undesirable byproducts may be formed; for example, electrolytic oxidation of phenol may produce some amount of chlorophenol.
An electrochemical method involving the generation of NO radicals in a medium containing nitric acid has been reported (R. N. Gedye, Y. N. Sadana, A. C. E. Edmonds and M. L. Langlois, J. Appl. Electrochem. 17, 731-736, 1987). The free radicals produced react with dissolved organic compounds and destroy them. The reaction requires a high concentration of nitric acid and the lectrolyte is very corrosive. It is therefore practically limited to destroying organic compounds dissolved in strong acid solutions.
Hydroxyl free radical is a very powerful, nonspecific oxidizing species which attacks most organic molecules as well as oxidizable inorganic molecules and ions (G. V. Buxton, C. L. Greenstock, W. P. Helman and A. B. Ross, J. Phys.

Chem. Ref. Data, 17, 513-759, 1988). Hydroxyl radicals may be produced by irradiation with Ultraviolet light of particles of titanum dioxide dispersed in water (C. Kormann, D. W. Bahnemann and M. R. Hoffmann, Environ. Sci. Technol, 25, 494-500, 1991) or by reaction of hydrogen peroxide with iron salts dissolved in mildly acidic solution, called Fenton's reaction.
Electrochemical production of hydroxyl radicals utilizing electrodes with various semiconducting surface compositions has been described (Chez, US Patent 4,676,878). Bianchi (US Patents 3,948,751 and 4,003,817) described electrodes wherein a titanium metal base is covered with an oxide coating which contains titanium dioxide, a large portion of a platinum group metal, and in some examples also niobium and tantalum. In this prior art, much higher anode potentials were required to produce hydroxyl radicals. In Weres et al (US Patent 5,364,508) have demonstrated that hydroxyl free radicals can be produced and organic substances dissolved in water can be oxidized at Ea Inventions related to the electrochemical treatment of effluent water to remove suspended solids, dissolved particles and bacterial contamination exist in literature. Reference may be made to Lin et al (US Patent 6,083,377) where nitrogenous compounds such as nitrate and ammonium etc., are treated by electrochemical transformations of the contaminant to nitrogen gas. Another reference may be made to Clarke et al (US patent 5,861,090) who disclosed a method for electrochemically remediating soil, clay or other media contaminated with organic pollutants using Fenton's reagent. The proposed technique is a method of electrochemical deployment of Fenton's reagent that can be applied

in-situ for the treatment of soils and clays. A method and apparatus for decontamination and purification of liquid mediums from toxic organic substances and other impurities is available (US Patent 6,296,744). This apparatus produces sterilizing solution, disinfectant, decontaminant, bleach, antiseptic detergent with the aim of disinfecting the liquid medium. An electrochemical cell comprising of nitric acid electrolyte containing silver ions as an electrochemically regenerable primary oxidizing species for decomposing organic waste matter is also known (Coulin et al, EP 0 297 738). Reference may be made to Mac Dougall etal (US patent 5, 662, 789) who invented a process for electrochemically collecting certain organic compounds from aqueous solutions in an immobilized and concentrated manner conducive to subsequent destruction. The method involves electrochemical formation of coupling products that are water insoluble and form deposits or films on working electrode surface. A process for galvanocoagulation through electrochemical formation of hydoxides of heavy metals as coagulants for removing through adsorption has been described by Tamarkin et al (US Patent 5, 658,450). Pressurized air, when passed through the cell, caused flotation and enhanced impurity removal. A process for mediated electrochemical oxidation of organic wastes without electrode separators is described by Farmer et al (US Patent 5,516,972). The metal salt mediators in sulphuric acid electrolyte in the presence of electrodes lead to efficient destruction of organic contaminants. Herbst et al (US Patent 6,241,861) described a water treatment tank for treating wastewater using electrochemical treatment process. The electrochemical process removes both suspended and dissolved solids in the

wastewater and heavy contaminants settle to the bottom while lighter than water contaminants are removed by vacuum from the top of the tank. In an invention related to the field of electrochemical wastewater treatment, Ritter eat al (US Patent 6,214,182) disclosed a device for treatment using electroflocculation. An electrochemical water treatment device for producing hydroxyl free radicals and decomposing by oxidation chemical substances dissolved in water was described by Weres et al (US Patent 5,439,577). It utilizes a novel electrode, which is capable of operation at sufficiently positive anodic potential to produce hydroxyl radicals.
In prior art, procedures applied to electrochemical treatment of different wastewaters exemplified that the electrochemical methods are applicable to wastewater treatment. Many inventions relate to development of electrodes, devices and methods for electrochemically producing oxidants, disinfectants, metal hydroxides etc., for removing or decomposing the specific chemical and microbial pollutants. No prior art recited above is able to completely oxidize organic substrates, nor oxidize in a non-specific manner a vide variety of chemical substances dissolved in water. However, the potential of a electrochemical method for treating actual wastewater such as tannery wastewater comprising of several nonspecific pollutants has not been explored; particularly, the electrochemical treatment of tannery wastewater from different stages of conventional treatment.
The main object of the present invention is to provide an improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, which obviates the drawbacks of the hitherto known equipment.

Another object of the present invention is to provide a process for the treatment of effluent such as tannery wastewater to obtain non-polluting water, which obviates the drawbacks of the hitherto known processes.
Yet another object of the present invention is to provide an improved conventional effluent treatment plant (CETP) being provided with an electrochemical reactor at stages such as the receiving sump, post anaerobic lagoon treatment, post secondary clarification and pre-final discharge.
Still another object of the present invention is to provide an electrochemical process for the treatment of tannery wastewater to obtain non-polluting water, which is an improvement of existing treatment for this wastewater.
The present invention seeks to provide the following technical result: an improvement in the conventional scheme of treatment of tannery wastewater, eliminate some of the treatment steps therein by way of inserting the proposed electrochemical reactor in place of one or more unit operations in conventional scheme and yet achieve desired treatment efficiency. The ability of electrochemical process to effect universal treatment for the variety of contaminants found in the wastewater is unique. This is exemplified by treating tannery wastewater from different stages of conventional treatment scheme shown in Fig.1 of the drawings. Advantageously the invention results in a compact treatment scheme with equal or better treatment efficiency, as insertion of electrochemical reactor would make some of the conventional unit operations down the treatment scheme in Fig.1 unnecessary. In another aspect of the

Present invention, it provides an improved wastewater treatment process for tannery wastewater that obviates the problems due to temperature dependence of biological nitrification processes. A typical batch electrochemical reactor of the present invention is shown in Fig. 2 of the drawings accompanying this specification. The electrochemical reactor comprises of a set of parallel electrodes (1,2) immersed in an electrolyte, such as tannery wastewater, and joined to a regulated Direct Current power supply. The anode (1) surface comprises of electrocatalytic metal, metalloxide or mixed oxide ( ceramic ) coating obtained as per the reported procedures in literature. A stainless sheet of similar geometry and area of anode was used as a cathode (2). The distance between anode and cathode can be fixed between 2-4 cm, but in the present case, a distance of 4 cm was found suitable. The electrolyte in the reactor is subjected to agitation through a magnetic needle (3) and magnetic stirring device placed below the reactor. The agitation can also be achieved by employing overheard stirrer. The electrochemical reactor sets in a forced chemical change through the electrolyte owing to the potential difference between anodes and cathodes. The reaction zones are frequently restricted to the surface of electrodes at electrode/electrolyte interfaces. The prepared electrodes were useful for electrochemical elimination of pollutants from tannery wastewater.
Accordingly, the present invention provides an improved effluent treatment plant useful for the treatment of tannery wastewater to obtain non-polluting water, which comprises an improved conventional effluent treatment plant (CETP), such

as herein been described, characterized in that the said CETP being provided in combination with an electrochemical reactor selectively at stages the receiving sump stage, post anaerobic lagoon treatment stage, post secondary clarification stage and pre final discharge stage and the said electrochemical reactor consisting of anode which is a plate of conductive metals having electrocatalytic coating such as metallic or ceramic and cathode of stainless steel of similar geometry as that of the anode and the distance of anode and cathode being kept in the range of 2- 4 cm and current density of the electrochemical reactor being kept in the range of 2-4A./dm .
In an embodiment of the present invention, wherein the electrochemical reactor essentially consists of an anode which is a plate of conductive metal, such as titanium, having electro catalytic coatings such as metallic or ceramic and cathode such as stainless steel of similar geometry as that of the anode. In another embodiment of the present invention, wherein the electrochemical reactor anode having electrocatlytic metallic coating is selected from one or a combination of two metals from Group VIII metals, particularly platinum and iridium.
In yet another embodiment of the present invention, wherein the electrochemical reactor anode having electrocatalytic ceramic coating is selected from coatings of oxides or sub oxides of Rh, Pd, Pb and Ti. In still another embodiment of the present invention, wherein the electrochemical reactor anode is selected from anode containing Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) an dTi/PbO2.
In still yet another embodiment of the present invention, wherein the said CETP being provided at the receiving sump stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2.

In a further embodiment of the present invention, wherein the preferred anode is either Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) for the treatment of raw tannery waste water at the receiving sump stage.
In another embodiment of the present invention, wherein the said CETP being provided at the post anaerobic lagoon treatment stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%);Ti/RhOx(50%)/Ti02(50%);Ti/PdO(70%)/Co3O4(30%).
In yet another embodiment of the present invention, wherein the preferred anode is Ti/PdO(70%)/Co3O4(30%) at the post anaerobic lagoon treatment stage.
In another embodiment of the present invention, wherein the said CETP being provided at the post secondary clarification stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co304(30%) and Ti/Pb02.
In still another embodiment of the present invention, wherein the preferred anode is selected from Ti/Pt(70%)/lr(30%), Ti/RhOx(50%)/TiO2(50%) at the post secondary clarification stage.
In still yet another embodiment of the present invention, wherein the said CETP being provided at the pre-final discharge stage with an electrochemical reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2.
In a further embodiment of the present invention, wherein the preferred anode is Ti/PdO(70%)/Co304(30%) at the pre-final discharge stage.

Accordingly, the present invention provides a process for the treatment of effluent to obtain non-polluting water, which comprises treating effluent in the improved effluent treatment plant as herein described, enabling simultaneous removal of ammonium (NH/), Total Kjeldhal Nitrogen (TKN) and Chemical Oxygen Demand (COD).
In an embodiment of the present invention wherein a process for the treatment of tannery waste water to obtain non-polluting water, comprises treating the effluent in the improved effluent treatment plant as herein described.
In another embodiment of the present invention , wherein the electrochemical reactor current density is in the range of 2 - 4 A/dm2.
In the present invention there is provided an improved effluent treatment plant wherein an electrochemical treatment process is provided whereby tannery wastewater is treated using anodes comprising of known electrocatalytic metallic or ceramic coating obtained by electrodeposition/thermal decomposition techniques. A voltage is applied between the anode and cathode and galvanostatic condition was obtained. The applied voltage is a function of conductivity of the tannery wastewater and in each case constant current as high as 2-4A/dm2 was attainable. Due to passing of current in the electrolyte, its temperature is raised to a maximum of 45-50°C. At the anode, there is discharge of chloride ions native to tannery wastewater with the formation of chlorine. Simultaneously electrolysis of water with the formation oxygen also occurs at anode. Hydroxyl radicals may also be produced under the conditions applied above. Chlorine or its derivative hypochlorous acid as well as oxygen based

radicals formed at anode react with pollutants such as ammonia, organic compounds including nitrogeneous compounds present in tannery wastewater. This results in reduction of ammonium, COD/TOC concentrations. At the cathode, metal, alkali and alkaline earth metal ions are discharged as their hydroxide precipitates and hydrogen is evolved, resulting in the increase of agitation. This resulted in flotation and scum formation that mainly contributed to colour removal from tannery wastewater. The originally unclear tannery wastewater due to presence of suspended solids became clear in due course of electrochemical process as heavy particles settled to bottom while lighter ones were lifted to electrolyte's top in the form of scum.
During electrochemical treatment of tannery wastewater, two main reaction pathways viz., direct electro-oxidation and indirect electro-oxidation, particularly in reference to ammonium removal may occur.
The direct reaction expressed as in Equation 1,
(Equation 1 Removed)
usually proceeds well over platinum anode, titanium electrodes covered with electrodeposited noble metals such as Pt, Ru, and Rh and their iridium alloys. The indirect anodic oxidation relies on the in-situ electrochemical production of oxidizing agents, particularly chlorine and hypochlorite. Indirect oxidation can be applied for wastewater containing high concentration of chloride ions. In this case, the free chlorine produced at anode reacts with ammonium ions to give

nitrogen gas as a final product that escapes into air readily, as shown in Equation 2 below:
(Equation 2 Removed)
Since tannery wastewater contains 2500 - 4500 mg/L chlorides, the indirect oxidation route may be profitably used for ammonia removal.
In an embodiment of the present invention the following different electrodes were prepared as per the reported procedures and used as anodes. The different anodes are:
1. Ti/Pt(70%)/lr(30%)
2. Ti/RhOx(50%)/Ti02(50%)
3. Ti/PdO(70%)/Co3O4(30%)
4. Ti/PbO2
The electrodes were obtained by electrodeposition or thermal decomposition in a way similar to the previously reported procedures (R.T.Atanasoski, B. Z. Nikolic, M. M. Jaksic and A. R. Despic, J Appl. Electrochem. 5, 155-158, 1975; US Appl. 549194, 1966; US 3 632 498,1978; US 3 711 385, 1973; Brit. Pat. 1 399 576,1973). The support metal substrate is of suitable geometry (plates) and made of a conductive metal, namely titanium. The metallic electrocatalytic coatings were obtained on to Ti substrate by electrodeposition from appropriate bath solutions containing precursor metal salts, generally metal halides. The electrocatalytic ceramic coating may be directly applied onto the support metal substrate by thermal decomposition of

precursor metal salt solutions/dispersions. The latter was obtained in repeated layers. The anodes in the present invention contain the electrocatalytic metallic coatings of one or a combination of two metals from Group VIII metals, particularly platinum and iridium in a pre-selected weight percent. The electrocatalytic ceramic-coated anodes constitute coatings of oxides or suboxides of Rh, Pd, Pb and Ti.
The following examples are given by way of illustration of the improved effluent treatment plant and process to obtain non-polluting water in greater detail and should not be construed to limit the scope of the present invention.
The removal efficiencies, detention times required to achieve the effluent standards, kinetic constants for ammonia and COD removal and energy consumption and energy requirements are reported for all different electrodes under different current conditions and for different types of tannery wastewater.
All experiments were conducted separately with each of the above-referred electrodes using four types of tannery wastewater collected at different stages of treatment, varying the conditions of electrochemical treatment.
The different types of tannery wastewater examined were:
• Raw tannery wastewater (after stage 2 in Fig.1)
• After anaerobic lagoon treatment (after stage 8 in Fig.1)
• After secondary clarification (after stage 11 in Fig.1)
• Final effluent (after stage 14 in Fig. 1).
It is therefore, to be intended that the invention is not limited to the specific examples reported herein below. Furthermore, it should be understood that the

effluent treatment plant and process, of the present invention, described herein might be extended to other types of suitable wastewaters also, in principle, particularly if the effluent contains ammonia and chloride together in significant quantities. It should be also borne in mind that other metal and ceramic deposits on the supporting metal substrate may also result in useful anodes in the effluent treatment plant and process of the present invention.
EXAMPLE 1
In this example, the electrochemical treatment of raw wastewater (after stage 2 in Fig.1) was carried out in the batch reactor using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co304(30%) and Ti/PbO2 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm-2. Throughout the duration of experiment, the reactor contents (electrolyte) were stirred continuously with the help of a magnetic stirrer. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may be required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOC), ammonium (NH4+), Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals.

The efficiency of removal of ammonia, TKN and COD from raw tannery wastewater is reflected through Fig.3 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (2) as a primary treatment unit for treating raw tannery wastewater from sump (1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2A/dm2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment are seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+, COD, TKN and S2- decreased substantially upon electrochemical pretreatment. This anode was replaced by the other anodes Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The first order kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 1-4.
Table-1: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from raw wastewater

(Table Removed)

Table-2: Detention times required for meeting effluent standards for TKN and COD using different types of electrodes in raw wastewater

(Table Removed)
Table-3: Energy consumption (EC) using different types of electrodes for the treatment of raw wastewater

(Table Removed)
Table-4: Energy requirement (ER) using different types of electrodes for the treatment of raw wastewater

(Table Removed)
It can be seen that the rate constants for ammonium removal (k[NH4+])
using Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%) and

Ti/PdO(70%)/Co304(30%) increased 2.6, 12.3 and 3.26 times when current is doubled from 2A/dm2 to 4A/dm2. The rate constant at Ti/RhOx/Ti02 is found more sensitive to current change. The k[NH4+] at Ti/Pb02 is higher than at other anodes, while COD removal using this anode is very insignificant. Further, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-2) decreased drastically as current is doubled. For example, Ti/RhOx(50%)/TiO2(50%) that required 25h at 2A/dm2, needed only about 2h at 4A/dm2. A similar trend was found with respect to COD removal also. The energy consumption (Table-3, EC, kWh/Kg TKN or COD) for COD removal increased drastically with increase in current density, while that for TKN removal decreased. Thus EC for TKN removal at Ti/RhOx(50%)/Ti02(50%) at 4A/dm2 is 4 times less compared to 833 kWh/Kg TKN at 2A/dm2. The anode performance as per EC for TKN and COD removal may be written in the order: Ti/PbO2 > Ti/Pt(70%)/lr(30%) ~Ti/PdO(70%)/Co304(30%) > Ti/RhOx(50%)/TiO2(50%), and Ti/RhOx(50%)/Ti02(50%)> Ti/PdO(70%)/Co304(30%)>Ti/Pt(70%)/lr(30%). The energy requirement (Table-4, kwh/m3 ) for the removal of TKN from 1m3 raw tannery wastewater followed the order Ti/PbO2>Ti/Pt(70%)/lr(30%) ~Ti/PdO(70%)/Co304(30%)>Ti/RhOx(50%)/Ti02(50%). Both Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) showed lower energy requirement at 4A/dm2.
Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 3 of the drawings, advantageously causes treatment of raw tannery wastewater thereby

making operational units down the scheme in Fig.1 unnecessary. However, due to higher initial pollution load in raw tannery wastewater the energy consumption, energy requirement and detention times are high for electrochemical treatment of this waste.
EXAMPLE 2
In this example, the electrochemical treatment of anaerobically treated
tannery wastewater (after stage 8 in Fig. 1) was carried out in the batch reactor
using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%);
Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm-2. Throughout the duration of batch experiment, the anaerobically treated tannery wastewater in the reactor was stirred continuously with the help of a magnetic stirrer provided below the reactor. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOC), ammonium (NH4+). Total Kjeldhal Nitrogen

(TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals.
The efficiency of removal of ammonia, TKN and COD from anaerobically treated tannery wastewater is reflected through Fig.4 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (8) for treating anaerobically treated tannery wastewater (after stage 8 in Fig. 1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2Adm"2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment can be seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+, COD, TKN and S2-decreased substantially upon electrochemical pretreatment. This anode was replaced by the other anodes Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co304(30%) and Ti/Pb02 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 5-8.

Table-5: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from wastewater after anaerobic lagoon treatment

(Table Removed)
Table-6: Detention times required for meeting effluent standards for TKN and COD using different types electrodes in waste water after anaerobic lagoon treatment

(Table Removed)
Table-7: Energy consumption (EC) using different types of electrodes for the treatment of wastewater after anaerobic lagoon treatment

(Table Removed)
Table-8: Energy requirement (ER) using different types of electrodes for the treatment of wastewater after anaerobic lagoon treatment

(Table Removed)
It can be seen that the rate constants for ammonium removal (k[NH4+j) using Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) increased 2.9 and 8.75 times when current is doubled from 2A/dm2 to 4A/dm2. The k[NH4+]) at Ti/PdO/Co304 is the highest. The rate constant at Ti/RhOx/Ti02 is found more sensitive to changes in current. The k[coo] at Ti/Pb02 is 0.001. However, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-6) decreased drastically as current is doubled. For example, Ti/RhOx(50%)/TiO2(50%) that required 8h at 2A/dm2, needed only about 3.35h at 4A/dm2 for TKN removal. Similarly, Ti/Pt(70%)/lr(30%) that required 4.3h at 2A/dm2, needed 1.5h at 4A/dm2. A similar trend was found with respect to COD removal also. The energy consumption (Table-3, EC, kWh/Kg TKN or COD) for COD removal remained somewhat invariant with increase in current density, while that for TKN removal decreased. The electrochemical reactor comprising Ti/PdO/Co304 consumed lowest energy, i.e 98kWh/KgTKN. Thus EC for TKN removal at Ti/RhOx(50%)/Ti02(50%) at 4A/dm2 is 3 times less compared to 1131 kWh/Kg TKN at 2A/dm2. The anode performance as per EC for TKN and COD
removal may be written in the order: Ti/PdO(70%)/Co304(30%) > Ti/Pt(70%)/lr(30%) > Ti/Pb02 > Ti/RhOx(50%)/Ti02(50%) and Ti/Pt(70%)/lr(30%) > Ti/RhOx(50%)/Ti02(50%) > Ti/Pb02. The energy requirement (Table-8, kwh/m3) for the removal of TKN from 1m3 anaerobically treated tannery wastewater followed the order Ti/PdO(70%)/Co3O4(30%) > Ti/Pt(70%)/lr(30%) > Ti/Pb02 > Ti/RhOx(50%)/TiO2(50%). Both anodes viz., Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/Ti02(50%) showed lower energy requirement for COD removal at 4A/dm2.
Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 4 of the drawings, advantageously causes treatment of anaerobically treated tannery wastewater thereby making operational units down the scheme in Fig.1 unnecessary. It may be seen in terms of higher rate constant, lower detention time, lower energy consumption and lower energy requirement, the Ti/PdO(70%)/Co304(30%) is a preferred anode for the treatment of anaerobically treated tannery wastewater.
EXAMPLE 3
In this example, the electrochemical treatment of tannery wastewater after
secondary clarification (after stage 11, Fig. 1) was carried out in the batch reactor
using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/Ti02(50%);
Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm-2. Throughout the duration
of batch experiment, the tannery wastewater after secondary clarification (after stage 11, Fig. 1) in the electrochemical reactor was stirred continuously with the help of a magnetic stirrer provided below the reactor. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOG), ammonium (NH4+), Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals.
The efficiency of removal of ammonia, TKN and COD from anaerobically treated tannery wastewater is reflected through Fig.5 of the drawings accompanying this specification. This figure illustrates usefulness of electrochemical reactor (12) for treating tannery wastewater after secondary clarification (after stage 11, Fig. 1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2Adm-2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment can be seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz.,
NH4+ , COD, TKN and S2" decreased substantially upon electrochemical pretreatment and comply with the corresponding discharge standards. This anode was replaced by the other anodes Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 9-12.
Table-9: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from wastewater after secondary clarification

(Table Removed)
Table-10: Detention times required for meeting effluent standards for TKN and COD using different types of electrodes in wastewater after secondary clarification

(Table Removed)
Table-11: Energy consumption (EC) using different types of electrodes for the treatment of wastewater after secondary clarification

(Table Removed)
Table-12: Energy requirement (ER) using different types of electrodes for the treatment of wastewater after secondary clarification

(Table Removed)
The rate constants for ammonium removal (k[NH4+]) followed the order: Ti/Pt(70%)/lr(30%) > Ti/RhOx(50%)/TiO2(50%) > Ti/Pb02 > Ti/PdO/Co3O4 The k[NH4+) at Ti/PdO/Co304 anode is 13 times more when current is doubled from 2A/dm2 to 4A/dm2. The k[NH4+]) at Ti/Pt(70%)/lr(30%) is the highest. The rate constant at Ti/PdO/Co3O4 is found more sensitive to changes in current. The k[coD] at Ti/Pb02 is 0.004. However, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-10) decreased as current is doubled. A similar trend was found with respect to COD removal also. Due to low strength
nature of tannery effluent from secondary clarifier, very low detention times as low as a few minutes were adequate for removal of TKN. In case of COD removal, except to Ti/RhOx(50%)/TiO2(50%), all other anodes still require longer detention periods. Thus, Ti/RhOx(50%)/Ti02(50%) requires only 16 min for bringing down COD from secondary clarifier effluent. The energy consumption (Table-11, EC, kWh/Kg TKN or COD) for COD removal decreased with increase in current density, while that for TKN removal remained invariant with Ti/Pt(70%)/lr(30%). The electrochemical reactor comprising Ti/Pt(70%)/lr(30%) consumed lowest energy, i.e 40 kWh/KgTKN at 2A/dm2 and 34 kWh/KgCOD at 4A/dm2. The energy requirement (Table-12, kwh/m3 ) for the removal of TKN from 1m3 tannery effluent from secondary clarifier followed the order > Ti/Pt(70%)/lr(30%) > Ti/RhOx(50%)/Ti02(50%) > Ti/Pb02 > Ti/PdO(70%)/Co304(30%). The anode, Ti/Pt(70%)/lr(30%) showed lower energy requirement for COD removal at 4A/dm2 while Ti/RhOx(50%)/TiO2(50%) showed lower energy requirement for COD as well as TKN removal at 2A/dm2.
Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 5 of the drawings, advantageously causes treatment of tannery effluent from secondary clarifier thereby making operational units down the scheme in Fig.1 unnecessary. It may be seen in terms of higher rate constant, lower detention time, lower energy consumption and lower energy requirement, the Ti/Pt(70%)/lr(30%) is a preferred anode for the treatment of tannery effluent from secondary clarifier.
However, Ti/RhOx(50%)/TiO2(50%) anode may also be used advantageously for the treatment of tannery effluent from secondary clarifier.
EXAMPLE 4
In this example, the electrochemical treatment of tannery wastewater (final effluent after stage 14 in Fig. 1) was carried out in the batch reactor using the Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/Ti02(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/Pb02 as anodes and stainless steel cathode and at different current densities namely 2 and 4 Adm"2. Throughout the duration of batch experiment, the final tannery effluent after tube settler (after stage 14, Fig. 1) in the electrochemical reactor was stirred continuously with the help of a magnetic stirrer provided below the reactor. Generally the electrolyte volume was kept constant, (1.0 L) but is a variable between 1-1.7 L as may required otherwise. During the experiments the samples were withdrawn from the batch reactor at different time intervals, more frequently during the initial period in order to build the kinetic data. In all a number of experimental runs were conducted to understand and define various aspects of process kinetics. The following parameters were determined in all runs as a function of time: pH, temperature, conductivity, chemical oxygen demand (COD), total organic carbon (TOC), ammonium (NH4+), Total Kjeldhal Nitrogen (TKN), sulphides and chromium; however the data is presented only for ammonia, TKN and COD removals.
The efficiency of removal of ammonia, TKN and COD from final tannery effluent is reflected through Fig.6 of the drawings accompanying this
specification. This figure illustrates usefulness of electrochemical reactor (15) for treating final tannery effluent after tube settling (after stage 14, Fig. 1). In this case, the anode was Ti/Pt(70%)/lr(30%) and stainless steel cathode held at 2Adm-2 for a period of 75 min. The changes in pH and the concentrations of all parameters viz., NH4+, COD, TKN and S2" that decreased substantially upon electrochemical pretreatment can be seen from the data in rectangular boxes provided on either side of the electrochemical treatment unit. It may be seen that all parameters viz., NH4+, COD, TKN and S2- decreased substantially upon electrochemical pretreatment and comply with the corresponding discharge standards. Particularly the COD and TKN concentrations are further reduced to below standards. This anode was replaced by the other anodes Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2 and the corresponding specific pollutant removal efficiency recorded in separate experiments. The kinetic constants for ammonia removal, detention times required to achieve effluent standards, energy consumption and energy requirements with respect to all the different electrodes are compiled Tables 13-16.
Table-13: Kinetic constants for different types of electrodes for elimination of NH4+ & COD from final effluent

(Table Removed)

Table-14: Detention times required for meeting effluent standards for TKN and COD using different types of electrodes in final effluent

(Table Removed)
Table-15: Energy consumption using different types of electrodes for the treatment of final effluent

(Table Removed)
Table-16: Energy requirement using different types of electrodes for the treatment of final effluent

(Table Removed)
The rate constants for ammonium removal (k[NH4+]) followed the order: Ti/PdO/Co304 > Ti/Pt(70%)/lr(30%) > Ti/PbO2 > Ti/RhOx(50%)/TiO2(50%). The k[NH4+)at Ti/Pt(70%)/lr(30%) anode is 3 times more when current is doubled from

2A/dm2 to 4A/dm2. The k[NH4+]) at Ti/RhOx(50%)/Ti02(50%) is the lowest and is insensitive to changes in current. The k[CoD] at Ti/PbO2 is 0.065. However, at higher applied current this anode showed signs of surface damage. The detention times that required for meeting the effluent standards for TKN and COD (Table-14) did not show decrease when current is doubled. But, the detention times decreased with respect to COD removal at higher current. Due to low strength nature of tannery final effluent very low detention times as low as a few minutes to half an hour were adequate for removal of TKN and COD. The energy consumption (Table-15, EC, kWh/Kg TKN or COD) for TKN removal decreased with increase in current density, while that for COD removal with Ti/Pt (70%)/lr(30%) increased. The electrochemical reactor comprising Ti/PdO/Co304 consumed lowest energy, i.e 12 kWh/KgTKN at 2 &4A/dm2. The energy requirement (Table-16, kwh/m3) for the removal of TKN from 1m3 final effluent followed the order Ti/RhOx(50%)/Ti02(50%) > Ti/Pb02 > Ti/Pt(70%)/lr(30%) > Ti/PdO(70%)/Co304(30%). The anode, Ti/PdO(70%)/Co304(30%) showed lower energy requirement for both TKN & COD removal at 2A/dm2 as well as 4A/dm2.
Therefore, insertion of electrochemical reactor comprising of any of the anodes described above into treatment scheme, as shown in Fig. 6 of the drawings, advantageously causes treatment of final effluent thereby making operational units down the scheme in Fig.1 unnecessary. It may be seen in terms of higher rate constant, lower detention time, lower energy consumption and lower energy requirement, the Ti/PdO(70%)/Co304(30%) is a preferred anode for the treatment of final effluent.

The performance of any anode in the present invention is a critical function of applied current density. Their choice should depend on the parameter of interest for meeting to discharge standard, lower detention time, lower energy consumption and lower energy requirement for removing the intended parameter. For example, we have seen that effective TKN removal necessitates application of higher current, while COD removal would require lower current with lower energy consumption for all types of tannery wastewater examined in the present invention. The main advantages of the present invention are :
1. Considerably reduced time period for satisfactory elimination of
ammonia from tannery wastewater compared to the conventional
biological processes.
2. Simplification, compactness and ease of operation accrued to the
design of tannery effluent treatment plants (ETP).
3. Allows simultaneous removal of ammonium (NH4+), Total Kjeldhal
Nitrogen (TKN) and Chemical Oxygen Demand (COD).
4. Allows simultaneous removal of several chemical impurities from
tannery wastewater.
5. The invention is useful for both final polishing of tannery wastewater as
well as an alternative to a step of biological denitrification of tannery
wastewater.

We Claim:
1. An improved effluent treatment plant useful for the treatment of tannery wastewater
to obtain non-polluting water which comprises an improved conventional effluent
treatment plant (CETP), such as herein been described, characterized in that the
said CETP being provided in combination with an electrochemical reactor
selectively at stages the receiving sump stage, post anaerobic lagoon treatment
stage, post secondary clarification stage and pre final discharge stage and the said
electrochemical reactor consisting of anode which is a plate of conductive metals
having electrocatalytic coating such as metallic or ceramic and cathode of stainless
steel of similar geometry as that of the anode and the distance of anode and cathode
being kept in the range of 2- 4 cm and current density of the electrochemical reactor
being kept in the range of 2-4A./dm2 .
2. An improved effluent treatment plant as claimed in claims 1, wherein the
electrochemical reactor essentially consists of an anode which is a plate of
conductive metal, such as titanium having electrocatalytic coating such as metallic
or ceramic and cathode stainless steel of similar geometry as that of the anode.
3. An improved effluent treatment plant as claimed in claim 1-2, wherein the
electrochemical reactor anode having electrocatalytic metallic coating is selected

from one or a combination of two metals from Group VIII metals, particularly platinum and iridium.
4. An improved effluent treatment plant as claimed in claim 1-2, wherein the
electrochemical reactor anode having electrocatalytic ceramic coating is selected
from coatings of oxides or sub oxides of Rh, Pd, Pb and Ti.
5. An improved effluent treatment plant as claimed in claim 1-4, wherein the
electrochemical reactor anode is selected from anode containing
Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2 (50%); Ti/PdO(70%)/Co3O4(30%) and
Ti/PbO2.
6. An improved effluent treatment plant as claimed in claim 1-5, wherein the said
CETP being provided at the receiving sump stage with an electrochemical reactor
comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/ TiO2
(50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2.
7. An improved effluent treatment plant as claimed in claim 6, wherein the preferred
anode is either Ti/Pt(70%)/lr(30%) and Ti/RhOx(50%)/TiO2 (50%).
8. An improved effluent treatment plant as claimed in claim 1-7, wherein the said
CETP being provided at the post anaerobic lagoon treatment stage with an
electrochemical reactor comprising of any of the anodes such as
Ti/Pt(70%)/lr(30%);Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%).

9. An improved effluent treatment plant as claimed in claim 8, wherein the preferred
anode is Ti/PdO(70%)/Co3O4(30%).
10. An improved effluent treatment plant as claimed in claim 1-9, wherein the said
CETP being provided at the post secondary clarification stage with an
electrochemical reactor comprising of any of the anodes such as
Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)/TiO2(50%); Ti/PdO(70%)/Co3O4(30%).and
Ti/PbO2.
11. An improved effluent treatment plant as claimed in claim 10, wherein the preferred
anode is selected from Ti/Pt(70%)/lr(30%); Ti/RhOx(50%) TiO2 (50%).
12. An improved effluent treatment plant as claimed in claim 1-11, wherein the said
CETP being provided at the pre-final discharge stage with an electrochemical
reactor comprising of any of the anodes such as Ti/Pt(70%)/lr(30%); Ti/RhOx(50%)
/ TiO2 (50%); Ti/PdO(70%)/Co3O4(30%) and Ti/PbO2.
13. An improved effluent treatment plant as claimed in claim 12, wherein the preferred
anode is Ti/Pt(70%)/ Co3O4(30%) .
14. A process for the treatment of tannery waste water to obtain non-polluting water,
which comprises treating effluent in the improved effluent treatment plant as
claimed in claim 1-13, enabling in the improved effluent treatment plant as claimed
in claim 1-13, enabling simultaneous removal of ammonium (NH4+), total Kjeldhal
nitrogen (TKN) and Chemical Oxygen Demand (COD).

15. A process for the treatment of tannery waste water to obtain non-polluting water,
which comprises treating the effluent in the improved effluent treatment plant as
claimed in claim 1-13.
16. A process as claimed in claim 14-15, wherein the electrochemical reactor current
density is in the range of 2 - 4 A/dm2.
17. An improved effluent treatment plant useful for the treatment of tannery wastewater
to obtain non-polluting water, substantially as herein described with reference to the
examples and drawings accompanying this specification.
18. A process for the treatment of tannery waste water to obtain non-polluting water,
substantially as herein described with reference to the examples and drawings
accompanying this speciation.

Documents:

598-del-2002-abstract.pdf

598-del-2002-claims.pdf

598-del-2002-correspondence-others.pdf

598-del-2002-correspondence-po.pdf

598-del-2002-description (complete).pdf

598-del-2002-drawings.pdf

598-del-2002-form-1.pdf

598-del-2002-form-19.pdf

598-del-2002-form-2.pdf

598-del-2002-form-3.pdf

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Patent Number

217355

Indian Patent Application Number

598/DEL/2002

PG Journal Number

15/2008

Publication Date

11-Apr-2008

Grant Date

26-Mar-2008

Date of Filing

30-May-2002

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SANTOSH NARAIN KAUL	NATIONAL ENVIRONMENTAL ENGINEERING REARCH INSTITUTE NAGPUR-440020, INDIA.
2	NAGESWARA RAO NETI	NATIONAL ENVIRONMENTAL ENGINEERING REARCH INSTITUTE NAGPUR-440020, INDIA.
3	TAPAS NANDY	NATIONAL ENVIRONMENTAL ENGINEERING REARCH INSTITUTE NAGPUR-440020, INDIA.
4	SHANTA SATYANARAYAN	NATIONAL ENVIRONMENTAL ENGINEERING REARCH INSTITUTE NAGPUR-440020, INDIA.
5	LIDIA SZPYRKOWICZ	ENVIRONMENTAL SCIENCS DEPARTMENT UNIVERSITY OF VENICE 30123, VENICE, ITALY.

PCT International Classification Number

C25B 9/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA