Title of Invention

"AN INTEGRATED PLANT FOR TREATMENT OF RAW WATER USING DISCARDED SLUDGES TO PRODUCE DRINKING WATER"

Abstract

This invention relate to an integrated plant for treatment of raw water using discarded aludgasfrom the plant for producing safe drinking water comprising a Sedimentation tank (11), having an inlet (11la) for introduction of raw water, an outlet (lib) of said sedunentation tank being connected to an inlet of a Rapid Mixing Device/Flash Mixer, which is connected to a clarifier/clarifloculator (3), the flash inixer (15) being connected to an coagulating agent source (2) and SRP(L) storage tank (7), the clarifloculator being connected to a Rapid Sand Filter Bed (12) to obtain purified drinking water, wherein the discarded sludge from the clarifloculator and back wash from the filter bed is stored in a sludge settling tank (4), the said tank conveying settled sludge into a Concentrated Sludge Storage (CSS) Tank (8), supernatant from the said tank being recirculated into the sedimentation tank (11), the said CSS tank (8) being in communication with a Sludge-Reagent-Reaction (SRR) chamber (5), to produce a Sludge-Reagent Product (SRP) followed by separation of SRP (Liquid) as supernatant (10).

Full Text

Field of Invention This invention relates to an integrated plant for treatment of raw water using discarded sludges to produce drinking water. Background of the invention It is generally known in the art that contaminants or impurities present in raw water from a surface water source normally consist of various categories. The first of such categories consist of substances dissolved in water, the second consisting of colloids and a third consisting of suspensions, such as particles of sand, clay and organic matter. The first category of contaminants are normally thrown out of solution and removed by chemical precipitation. The second category, namely collodial particles, are removed from the dispersion medium by the process of flocculation. The third category of contaminants are removed by operations, such as screening, plain sedimentation and flotation, For this purpose, water treatment plants normally consisted of an intake with a coarse screen for removal of large floating materials, which are prevented from entering into the system. The intake further comprised a pump for delivery of raw water from the source to the treatment system. The raw water, which is turbid in nature, may flow through a fine screen for removal of bigger particles, before entering into a primary clarifier. The primary clarifier is essentially a sedimentation tank, and where the raw water is retained over a retention period of 4 to 12 hours so that the heavy particles settled down, which are then removed as a sludge therefrom. A coagulant is added to the partially treated raw water, which is then subjected to the step of rapid mixing in a tank called flush mixer so as to provide even distribution/thorough mixing of coagulant with raw water. Such a mixer is then introduced into a flocculator and subjected to the step of slow mixing to from floes of the colloidal particles. The partially treated water thereafter introduced into a secondary clarifier and retained there for a pre-determined period where the colloidal particles in the form of floes are settled at the bottom of the clarifier. The clarified water is then passed through a filtration bed and then subjected to the step of disinfection with the help of known disinfectant before the same is supplied as safe drinking water to the consumer. The sludge settled at the bottom of the clarifier, as well as backwash from filter bed, have hitherto been discarded as waste in conventional plant as herein referred in Indian Patent No. 170107. The conventional plant is an integral part of the Integrated Plant featuring the present invention. The diagram of the conventional part of the plant is given in figure-I. The inventive features in the present invention start where the conventional Plant as described above ends and relates to the use of the discarded sludge which are given appropriate treatment to transform the same into a mass called Sludge-Reagent Product (SRP). To this end, the conventional part of the Integrated plant is operated for a minimum pre-determined period to produce enough discarded sludge which are collected, settled, chemically treated to produce a new product called Sludge-Reagent) Product (SRP). The product is separated into two parts-liquid and solid, using gravitational forces. The solid part is discarded. The liquid part of the product i.e. SRP(L) is used in combination with parent coagulant to effect desired coagulation / floccation followed by clarification. This entire process leading to production of SRP(L) takes place in the non-conventional part of the Integrated Plant. In this non-conventional part of the Plant lies the crux of the simple but innovative process of the present invention. As taught from the Patent Application No. 170107 the amount of coagulant added to the raw water is dependant on the pH and turbidity of raw water. It has been found that the pH of raw water can vary between 5.5 to 9, which upon treatment should have a basic pH or a pH of 6.5 to 7.5. Thus, and as by way of example, alum may constitute one of the coagulants in the instance where the raw water has an alkaline pH. Reference is made hereinafter to alum as the coagulant, which constitutes one of the most widely used coagulant. However, such a reference is made only by way of an exemplary embodiment to explain, and as subsequently described herein, the theoretical aspect involved in the removal of colloidal particles from the raw water, it being simultaneously understood that any other known coagulant can be employed in the water treatment plant and process of the present invention. Reference is now made to : Firstly, to the chemical aspects relating to the art of removal of colloidal particles and secondly, to the chemical activity (ion exchange characteristics) of the colloidal particles in the discarded sludge becoming positively charged with the release of Al+3-ions which together act as coagulants by way of neutralizing negatively charged colloidal particles in raw water. This in turn, helps formations of floes and makes separation of colloidals possible. Appreciation of these two phenomena are essential pre-requisites for better understanding of the conventional treatment plant integrated with the present Treatment Plant using discarded sludge. In case of the former, upon addition of alum or aluminium sulphate to raw water, a reaction is caused resulting in the formation of Al3+-ions, aluminium hydroxide and sulphuric acid and, whereby, the pH of raw water is reduced, though not appreciable. Thus, and as by way of example, if the pH of raw water is 7, then the pH is reduced to approximately 6.8 due to the formation of aluminium hydroxide caused by the reaction of aluminium sulphate with water. However, if the raw water has a pH of 5.5, alumimium sulphate as a coagulant would not have the same economic benefits as the addition thereof will further reduce the pH of raw water, and sufficient aluminium hydroxide would not be available for floe formation. Even, if the raw water has a pH of 7, and insufficient amount of alum is added, the amount of A13+ is not sufficient to cause an efficient removal of the colloidal particles. Simultaneously, if an excess quantity of alum is added, the pH of the raw water would rapidly reduce and, thereby, resulting in a less formation of aluminium hydroxide. Thus, normally only the optimum dose of the coagulant is added so as to allow the formation of A13+ and aluminium hydroxide. It is generally known that the colloidal particles get negatively charged by way of a natural arrangement of negative ions around them. Thus, two phenomenons occur in the formation pf floe. One of the phenomena is that of collusion phenomena imparted by the action of stirring within the flocculator. The other phenomenon is the electrical kinetic phenomena. Upon addition of aluminium sulphate to raw water, Al3+-ions are released in conjunction with the formation of aluminium hydroxide. Thus, the colloidal particles, which have a negative charge, attract the positively charged ions and, whereby, the colloidals particles are destabilized and become neutral. The slow mixing allows such destabilized colloidal particles to physically form bigger floes. The sludge discharged from the secondary clarifier thus consists of destabilized colloidal particles having aluminium hydroxide floes physically attached thereto. Such a sludge was hitherto discharged as a waste. In case of the later, the fact that sludge discharged from the clarifier consists of settleable solids and colloidal floes, and where the colloidal particles are in destabilized state. The destabilized colloids are recharged with positive charges with the release of Al3+-ions. The presence of the settleable solids in the sludge is not important for purposes of the present invention. However, the presence of the destabilized colloidal floes is important in that such destabilized colloids are treated for purposes of recycling into the process as explained hereinafter. It has been tought in the earlier patent referred herein that the destabilized colloidal floes contain aluminium either in the form of aluminium ions or alwninium hydroxide physically and electro chemically entrapped therein. Qne of the^epjec|iojleof the present invention concerns with release of such aluminium from the sludge which regains its charge and emerges as aluminuium ions. The aluminium ions are entrapped electro chemically, whereas, aluminium hydroxide is entrapped physically in the sludge. The sludge discharged from the clarifier has a pH depending on the pH of the raw water. In accordance with this invention, the sludge is introduced into a rapid mixing tank and, wherein, a reagent is added so as to cause a lowering of the pH of the sludge. The reagent comprises preferably an acid. Thus, and in the instance where the coagulant comprises alum or aluminium sulphate, which is the example described earlier herein in order to exemplify the invention, the reagent employed for causing a reducing of the pH of the slurry may be sulphuric acid. The presence of sulphuric acid causes an electro chemical release of the aluminium ions from the sludge. Thus, upon addition of sulphuric acid, IT" ions and whereby, aluminium ions are released therefrom and H"1" ions are attracted thereto. The result of H+ ions being attracted to and electrochemically bonded with the colloidal particles is that the colloidal particles acquire a positive charge, and the aluminium ions released from the colloidal particles possess a positive charge. Thus, the treated sludge consists of positively charged colloidal particles and positively charged aluminium ions, which is suitably introduced as a coagulant into the system and provide a better floe formation with the negatively charged colloidal particles present in the raw water. In accordance with the prior art teaching, the pH of the Sludge-Reagent-Product (SRP) is reduced to 4 or below. Preferably, the treated sludge has a pH of 1 to 4. If the treated sludge has a pH of greater than 4, which will arise in the instance of addition of a lesser quantity of sulphuric acid to the sludge, the amount of available H +ions would not be sufficient to release the A13+ ions from the colloidal particles. Simultaneously, if the sludge is treated such that the pH is less than 1, then the amount of sulphuric acid would be excessive. Thus, when such a sludge is employed as a coagulant and recycled into the system, the pH of the raw water would be reduced and causing an adverse effect on the formation of floes. The present invention is an advanced development over the former invention vide Patent No. 170107 wherein the applicant was Sudhendu Kumar Biswas, who is one of the applicants in the present application. A disadvantage associated with the aforesaid known process in Patent No. 170107 is that the efficiency reduces with the number of recycles necessitating repetition of the process over and again. In other words, the process is to be operated in batches. The table herein below will indicate as to how the efficiency reduces with the number of recycles. Table -1 Treatment efficiency of Sludge-Reagent-Product (L) to treat Raw Water having Turbidity of 75 NTU. (Table Removed) In the present invention i.e. "An Integrated Plant for Treatment of raw water using discarded sludge from the said plant", disadvantages inherent in Patent No. 170107 is obviated rendering the same a continuous process and thus enabling operation of the plant hassle free and simple, without any loss of efficiency. OBJECTS OF THE INVENTION 1. An object of this invention is to propose an Integrated Plant for treatment of raw water to produce water of quality conforming to the standard prescribed for safe drinking water. 2. Another object of this invention is to propose an Integrated Plant for treatment of raw water and, wherein, the sludge hitherto rejected as a waste is treated and recycled as a coagulant of higher efficiency. 3. Yet another object of this invention is to propose an Integrated Plant for treatment of raw water and, wherein the sludge hitherto rejected as a waste is treated and recycled as a coagulant and provides a substantial reduction in the cost of treatment. 4. Still another object of this invention is to propose an Integrated Plant for treatment of raw water and, wherein, the sludge hitherto rejected as a waste is treated and recycled as a coagulant which provides a substantial reduction in volume of sludge leading to handling of sludges simpler and economical. 5. A further object of this invention is to propose an Integrated Plant for treatment of raw water and, wherein, the sludge hitherto rejected as a waste is treated and recycled as a coagulant and whereby the sludge discharged has mostly inert materials contained therein, disposal of which is simple and does not pose any environmental hazards. 6. Another object of the invention is to propose an Integrated Plant for treatment of raw water and, wherein, supernatant from the Sludge Settling Tank is recycled as raw water thereby reducing loss of water at plant site to an extent of 5-8% leading to overall physical and financial efficiency of the plant. 7. A still further object of this invention is to propose an Integrated Plant for the treatment of raw water and, wherein, the sludge hitherto rejected as a waste is treated and recycled as a coagulant, which is simple. 8. Yet another important object of the invention is that in the event of the above recycling, discharges of sludge to natural bodies of water or on land becomes negligible resulting in substantial reduction in Environmental Pollution. 9. A still further object of the invention is to propose an Integrated Plant for treatment of raw water and wherein, the colloidal phenomena as observed herein is fundamental and opens areas of fundamental research studies. DESCRIPTION OF INVENTION The present invention has provided an Integrated Treatment Plant for treatment of raw water to use said treated water as potable water, comprising the following features of: i) a sedimentation tank having an inlet for introduction of raw water. ii) an outlet of the sedimentation tank is connected to coagulating agents such as alum and Sludge-Reagent-Product (Liquid), the said outlet is also being connected to an inlet of a Rapid Mixing device for thorough mixing of coagulating agents with raw water. iii) raw water thoroughly mixed coagulating agents have an outlet from the Rapid Mixing Device, enters into a clariflocculator for slow mixing resulting floe formation, which settles down as sludge; clarified water through outlet of the said clariflocculator enter into Rapid Sand Filter, sludges settled at bottom of the said clarifier is discarded as waste; back-wash water from Rapid Sand Filter is also discarded as waste. iv) Filtered water from the Rapid Sand Filter is collected through an outlet, disinfected with suitable disinfectant and supplied to the consumers for drinking purpose inter alia. It is to be understood for the proper understanding of the invention that the processes of collection of discarded sludges, their chemical treatment, separation of the liquid part of the product from that of solid, use of the liquid part as coagulant constitute features of the invention summarized as follows:- 1. discarded sludges are being collected and allowed settlement in a Sludge Settling (SS) Tank, the said SS tank is having outlet for clear supernatant and is connected to the raw water channel for recycling and another outlet for the sediment (concentrated sludge). 2. a Concentrated Sludge Storage (CSS) tank with an inlet for settled sludge from SS tank and an outlet from CSS connected to inlet of Sludge Reagent Reaction (SRR) Chamber, the said SRR Chamber inlet is also connected with the Sludge Reagent Tank. 3. the said Sludge Reagent Reaction Chamber, where, reagent reacts with sludges, has in outlet for the product of the reaction and is connected to the inlet of the Sludge-Reagent-Product (SRP) settling chamber. 4. In a SRP settling Chamber, the liquid part of the product is separated from that of the solid part, the said SRP settling chamber is having outlets for SRP(L) as well as for SRP(S), the outlet for SRP(L) is connected to inlet of the SRP(L) storage tank, the SRP(L) storage tank is in turn connected to the raw water channel, the said SRP(L) hereinafter is used as coagulant. 5. a SRP(S) - Lime Mixing Tank with an inlet for SRP(S) from SRP settling chamber as well as an inlet for lime from lime tank, the mixing tank has an outlet for the mixer and connected to the inlet of Sludge Drying Bed. 6. a Sludge Drying Bed is having an outlet for leach ate to be disposed of suitably on land and/or natural water bodies, the dried sludge cake is also disposed of preferably by Sanitary Landfill, According to this invention there is provided an integrated plant for treatment of raw water using discarded sludges from the plant for producing safe drinking water comprising: i) a Sedimentation tank having an inlet for introduction of raw water, ii) an outlet of said sedimentation tank is connected to an inlet, of a Rapid Mixing Device, outlet of which is connected to a clarifloculator, iii) inlet of the Rapid Mixing Device is connected to an coagulating agent source such as alum and SRP(L) storage tank, iv) the outlet of the clarifloculator is connected to a Rapid Sand Filter Bed to obtain purified filtered water and a disinfectant is added to the filtered water to produce safe drinking water, v) characterized in that the discarded sludge from the clarifloculator and back wash from the filter bed is stored in a sludge setting tank, the said tank having an outlet for conveying settled sludge into a concentrated sludge storage (CSS) Tank, supernatant from the said tank is recirculated into the inlet of sedimentation tank, vi) she said CSS tank is being in communication with a sludge-reagent-reaction (SRR) chamber which have inlets for receiving the concentrated sludge and a reagent such as acid from Sludge Reagent Tank to produce a Sludge-Reagent-Product (SRP) which is fed from said reaction chamber into a SRP Settling chamber wherein SRP (Liquid) is separated as supernatant (10) from the SRP (solid) as sediment, an outlet of said SRP settling chamber is connected to SRP (L) storage tank. DESCRIPTION WITH REFERENCE TO ACCOMPANYING DRAWING Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawing and wherein Fig.1 illustrates a schematic drawing of the conventional water treatment plant and Fig 2 illustrates a proposed water treatment plant with SRP technology according to the present invention, Referring to Pig. 2, raw water is fed to a plain sedimentation tank 11 through an inlet (lla). Partially treated water from plain sedimentation tank is fed to the inlet of a Rapid mixing device (15) and therefrom to clarifoculaior (3). Sedimentation tank (11) causes a separation of sediments or coarser particles present in raw water. The Rapid mixing device causes uniform mixing of coagulants with raw water. Specifically, in accordance with this invention, a Sludge-Reagent-Product (Liquid) SRP(L) from storage tank (7) feeds SRP(L) to the raw water prior to being fed to a Rapid mixing device, fa a likewise a coagulating source (2), such as alum, is also fed to raw water prior to entry into the said mixing device. However, and with an important concept of this invention, if 100% of me coagulating agent is added to raw water in me absence of SRP(L), only 10-20% of the optimum dose is added as the remainder of the coagulating agent now constitutes me product of sludge, which was hitherto a waste, fed from storage tank (7). SRP(L) frotu tank (7) and only 10 to 20% of me optimum dose of alum from coagulating source (2) is fed to raw water uniformly mixed before it enters into clarifier (3). Clarifier (3) has an outlet (3a) for clarified water which then passes through a sand filter bed (12) and discharged as treated water. A disinfectant is added to the treated water. Reference is made in particular to the sludge discharged from clarifier outlet (3b), Such a sludge together with back wash water from outlet (12a) of sand filter bed (12) is fed to a sludge settling tank (4) to cause a separation of the supernatant from the concentrated sludge. The supernatant is recycled as raw water, whereas the concentrated sludge flows to a storage tank (8). The concentrated sludge from storage tank (8) is fed to a Sludge-Reagent-Reaction Chamber (5) together with a reagent, such as an acid, fed from reagent source (9). The reagent reacts with the sludge to produce a mass called Sludge-Reagent-Product (SRP), which is then fed to a SRP Settling Chamber (6)> and where the supernatant SRP(L) is separated from the solids SRP (S). The supernatant SRP(L) is fed to storage tank (7) and the solids SRP(S) is fed to a sludge drying bed (14) after mixing with lime from a lime tank (17) in a SRP (S) Lime Mixing Tank (16). The leachate from bed (14) is disposed of on land for irrigation and / or natural bodies of water, and the sludge on drying from bed (14) is discarded. The conventional plant for treatment of raw water is shown in the schematic flow sheet diagram, wherein it is to be noticed that present invention originates by using the discarded sludge from the clarifoculator and back wash water from the filter bed as in the prior art and the said utilizing of the discarded sludge m integrated with the prior invention in this field by feeding SRP(L) from the SRP(L) Storage Tank with the raw water after sedimentation Reference is now made to Table 2 which shows the turbidity of treated water by the Integrated Treatment Plant of the invention by using SRP(L) and various doses of alum as a continuous process. WE CLAIM; 1. An integrated plant for treatment of raw water using discarded sludges from the plant for producing safe drinking water comprising: i) a Sedimentation tank (11) having an inlet (lla) for introduction of raw water, ii) an outlet (lib) of said sedimentation tank is connected to an inlet of a Rapid Mixing Device, outlet of which is connected to a clarifloculator (3), iii) inlet of the Rapid Mixing Device (15) is connected to an coagulating agent source (2) such as alum and SRP(L) storage tank (7), iv) the outlet (3a) of the clarifloculator is connected to a Rapid Sand Filter Bed (12) to obtain purified filtered water and a disinfectant is added to the filtered water to produce safe drinking water, v) characterized in that the discarded sludge from the clarifloculator and back wash from the filter bed is stored in a sludge setting tank (4), the said tank having an outlet for conveying settled sludge into a concentrated sludge storage (CSS) Tank (8), supernatant from the said tank is recirculated into the inlet (lla) of sedimentation tank (11), vi) the said CSS tank (8) is being in communication with a sludge-reagent-reaction (SRR) chamber (5) which have inlets for receiving the concentrated sludge and a reagent such as acid from Sludge Reagent Tank (9) to produce a Sludge-Reagent-Product (SRP) which is fed from said reaction chamber (5) into a SRP Settling chamber (6) wherein SRP (Liquid) is separated as supernatant (10) from the SRP (solid) as sediment, an outlet of said SRP settling chamber is connected to SRP (L) storage tank (7). 2. An integrated plant for treatment of raw water as claimed in claim 1 wherein an outlet for SRP (S) is connected to SRP (S) Lime Mixing Tank (16), situated between SRP Settling Chamber (6) and a Sludge Drying Bed (14). 3. An integrated plant for treatment of raw water as claimed in claim 1 wherein the said SRP (S) Lime Mixing Tank (16) having inlet for lime from lime tank (17) and an outlet from SRP (S) Lime Mixing Tank (16) into a Sludge Drying Bed (14). 4. An integrated plant for treatment of raw water as claimed in claim 1 wherein the Rapid Mixing Device (15) is a Flash Mixer. 5. An integrated plant for treatment of raw water using discarded sludges from the plant to produce safe drinking water as herein described and illustrated.

Documents:

535-del-2001-abstract.pdf

535-del-2001-claims.pdf

535-DEL-2001-Correspondence-Others-(03-05-2010).pdf

535-del-2001-correspondence-others.pdf

535-del-2001-correspondence-po.pdf

535-del-2001-description (complete).pdf

535-del-2001-drawings.pdf

535-del-2001-form-1.pdf

535-del-2001-form-13.pdf

535-DEL-2001-Form-15-(03-05-2010).pdf

535-del-2001-form-19.pdf

535-del-2001-form-2.pdf

535-del-2001-form-3.pdf

535-del-2001-form-4.pdf

535-del-2001-gpa.pdf

535-del-2001-petition-others.pdf

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