Title of Invention

"A PROCESS FOR RECOVERY OF SALT FROM SALT LADEN WATER CONTAINING DISSOLVED ORGANICS FOR REUSABLE OPTION"

Abstract

The present invention provides process for recovery of salt from salt laden water containing dissolved organics using Oxidising agent under acidic condition to remove the dissolved organics. Other chemical and biological impurities present in the water containing salt and dissolved organics can be removed by passing the same through activated carbon of specific characteristics. Water free from dissolved organics, evaporated under sun light provide salts for reusable option.

Full Text

The present invention relates to a process for recovery of salt from salt laden water containing dissolved organics for reusable option. Field of the Invention More particularly, the present invention provides a process for the purification of water containing common salt and dissolved organics using chemical method, whereby the recovered common salt can be reused for industrial purpose. This process has enormous potential application in the treatment of water, generated from various industries including leather, dyeing, food, and chemicals, for not only rendering the industrial effluents free from dissolved organics and salts, but also recovering the salt for reuse. Background of the Invention Salt laden wastewater along with dissolved organics when discharged into open land migrates through the soil matrix and gets exchanged for ions and absorbed on the core of the soil particles. On exceeding the threshold concentration, the cation exchange capacity of the soil is reduced and this in turn affects the fertility and biodiversity. As reported by Nandy (Symposium on Raw Hides and Skins Curing and Preservation, CLRI, 71-75, 1957), the salt solution gets contaminated with blood, manure and other substances leading to a raise in pH not conducive for the growth of microorganisms. These impurities impart colour to the salts after evaporation and thus hinder the preserving property of the salt. Evaporation using solar pans, with cost effective means of available abundant solar energy, producing salts with other impurities was also reported by Krishnamurthy et al (Journal of American Leather Chemists Association, 71, 36-40, 1976). Nandy (Symposium on Raw Hides and Skins Curing and Preservation, CLRI, 71-75, 1957) reported that the presence of impurities restricts the reuse of the salts recovered. Simoncini (Symposium on fuller and Better Utilization of hides, 35-48, 1964) suggested the use of hypochlorite, sodium carbonate and naphathalene to denature the activity of microorganisms. Further Sehgal (Journal of Leather Science 23, 236-239, 1976) reported that repeated washing of the salt with saturated sodium chloride solution reduces the quality of salts obtained from solar evaporation. The method is effective and depends on the solar energy. Moreover the rate of evaporation is hindered by the presence of impurities like proteinous compounds etc. Evaporation during rainy season is very difficult and it requires large land area for storing the wastewater necessitating for high investment cost. Another well known method of treatment of water containing only salt is chemical coagulation. As reported by Sekaran et al (Leather Science, 30(6), 191-192, 1983), precipitation of sodium chloride from saturated solution of scraped salt produce salts for reuse. Sekaran et al (Pakistan Leather Technology Journal, December, 41-50, 1994), comparing the efficiency of various coagulating agents like alum, lime and mixture of both, reported that only the alum coagulation removes considerable quantity of pollution load of salt laden water. About 66% BOD, 70% COD and 89% SS and 80% of dissolved protein has been removed by this method. The major limitation in using this process is requirement of high quantity of coagulants for precipitation and the disposal problem of sludge generated in this system. Further, the presence of dissolved organics limits the reuse of recovered salt because of poor quality. The next possible method is the biological method. As reported by Nandy (Symposium on Raw Hides and Skins Curing and Preservation, CLRI, 71-75, 1957), the efficiency of the biological method is poor because of the fact that the growth of the microbial species is highly restricted by the high saline nature of wastewater. Moreover, the salt recovered from this process is highly coloured and not always sufficient to meet the quality standards. Photosynthetic organisms including higher plants, algae and animal tissues from processing unit of food and meat are the major sources for dissolved organics in water and or wastewater. Diss6lved organics can also be released to the environment during decomposition and growth of the organisms, thereby contaminating the water. Moreover, the dissolved organic chemicals often interfere with the analysis of the pollutants present in water and also tend to disrupt the water purification processes in water treatment plants by clogging filters, settling on resin beds, etc. In salt recovery system, the presence of dissolved organics in the saline water, produces coloured salts upon solar evaporation. As a result, there is no end use of the salt recovered. Several attempts have, therefore been made to remove dissolved organics from water containing common salt. The following treatment options have conventionally been in practice. 1. UV irradiation 2. Carbon filtration process (activated carbon treatment) 3. Use of oxidizing agents Thomson et al (Journal of Water SRT-Aqua, 51, 297-306, 2002) reported that the application of UV irradiation for removal of dissolved organics would not work if the water is saline. As reported by Yip and Konasewick (Journal of water pollution control (Can.), 6, 14-18, 1972) and Whiteby et al (Journal Water Science Technology, 27 93-4), 379-386, 1993), UV lamps may become fouled on continuous usage for more than 2 years, the residues produced by UV irradiation in the presence of other oxidizing agents result in toxicity, necessitating further treatment. A combination of UV irradiation and activated carbon filtration has however been reported to remove more than 50% of dissolved organics present in water. Sekaran et al (Indian patent Application No. 380 Del 96) used rice bran based activated carbon for the removal of dissolved organics. The activated carbon used for this purpose had surface area in the range of 220-240 m /g as well as the macropore and mesopores in the ratio ranging between 1:0.6 and 1:1. Reference may be made to Bonne et al (Water Supply, 2(1), 139-146, 2002) and Frank DeSilva (Water Quality Products Magazine, 1-2, 2000), who observed that the continuous usage of activated carbon for a period of more than 6 months for removal of dissolved organics results in fouling of carbon granules requiring frequent backwash. As reported by Braghetta et al (Water Supply, Vol 1 No 5-6 pp 331-339, 2001), it was possible to remove only 11 and 27% of dissolved organics and colour respectively by using carbon filtration process. The above limitations have prompted the researchers to explore the possibilities of using oxidizing agents for the purpose of removing dissolved organics from water. There has been a report (Tech Brief: In: National Drinking water clearing house Newsletter, No. 12, 1-4, 1999) stating that though the efficiency of ozonation in removal of dissolved organics is 100%, the major disadvantages of using ozone lies in its toxic nature and high cost. Another major limitation associated with the process is that ozone oxidizes the organics present in water producing aldehydes and ketones, necessitating for the post treatment of the treated water. It has however been possible to remove 70-80% of dissolved organics by using combination of ozonation and activated carbon filtration technique, as reported by Ervin Orlandini et al (Water Science and Technology Vol 35 No 7 pp 295-302, 1997) and Yasushi Takeuchi, et al (Water Science and Technology Vol 35 No 7 pp 171-178 1997) and Joanne Sketchell et al (Water Quality Research Journal of Canada, 34(4): 615-631 1999). Another viable method for removal of dissolved organics is by hydrogen peroxide. Miller et al (Journal of Water Research, 29(10), 2353-2359, 1995) reported that the reaction of hydrogen peroxide with organics is dependent on various environmental factors such as pH, temperature, dose, reaction time, and/or catalyst addition. Siegrist (Environmental Protection Agency, 542-N-00-006, 37, 1-3, 2000) reported that Fenton's reagent is effective under very acidic pH (pH 2-4) and becomes ineffective under moderate alkaline condition. Thus this option has its own limitation of flexibility of reaction conditions. It has been possible to overcome this limitation by using catalysts such as iron, copper and manganese, that enhances the oxidizing capacity of hydrogen peroxide. As reported by Collins and Gordon (Journal of American Chemical Society, 111, 4511-4513, 1989), hydrogen peroxide catalyzed with copper is only used for purification of water containing cyanides. Use of Fenton's reagent for removal of dissolved organics was reported by Teel et al (Water Research, 35(4), 977-984, 2001). Reference may be made to Carr et al (US Patent No. 4604214,1986), who recommends the use of Fenton's reagent as the best method for removal of dissolved organics without any harmful effects. However, the use of this reagent in presence of common salt is associated with certain limitations. Fenton's reagent generates hydroxyl radicals which hydroxylate the organic compounds present in the wastewater to ease their degradation. The generation of hydroxyl free radical is accompanied with the formation of trivalent iron (ferric iron), which will be spontaneously converted into ferrous iron by reacting with one of the free radicals generated during the course of the reaction. In the presence of sodium chloride the ferric iron is poisoned by chloride ion making difficult to revert back to ferrous ion and more often it leads to the formation of trivalent iron oxide. Thus the accumulation of ferric oxide in the system hinders further oxidation, resulting in the reduced rate of removal of dissolved organics. Thus, the major limitation associated with all the aforesaid water treatment processes is that the presence of any common salt adversely affects the removal of dissolved organics. Attempts are therefore being made to explore possibilities for developing suitable process to remove dissolved organics as well as common salt, simultaneously present in water, whereby the recovered common salt can be reused. No prior art is available on removal of dissolved organics in water and or wastewater in the presence of common salt. Objects of the Invention The main objective of the present invention is to provide a process for recovery of salt from salt laden water containing dissolved organics for reusable option, which obviates the drawbacks stated above. Another objective of the present invention is oxidizing the dissolved organics in the water containing salt to the extent of more than 99%. Yet another objective of the present invention is to use activated carbon having both mesopores and micropores (1:0.6 and 1:1) to ensure oxidation of organics present in the wastewater. Summary of the Invention Accordingly the present invention provides a process for recovery of salt from salt laden water containing dissolved organics for reusable option which comprises i. adjusting the pH of the water containing both dissolved organics and salt to 3.0- 5.3 by known method, ii. treating the water, as obtained in step(i) with 0.1 -1.0% w/v, of known oxidizing agent for a period of 2-4 hours followed by passing the same through 70-80 % w/v, of activated carbon having surface area in the range of 220 -240 m /g by known method for a retention period of minimum 6 hours and collecting the resulting water by known method to obtain saline water free from dissolved organics iii. drying the saline water, as obtained in step(ii) by conventional method to obtain salt (Common salt) for reusable options. In an embodiment of the present invention, the known method of separation may be selected from decanting, filtration, settling. In another embodiment of the present invention, the activated carbon used for oxidizing dissolved organics may be such as rice bran based carbon with surface area in the range of 220 -240 m2 /g, macropore and mesopores in the ratio between 1:0.6 and 1:1. In yet another embodiment of the present invention, the oxidizing agent used may be selected from potassium permanganate, hydrogen peroxide, ozone, Fenton's reagent, either individually or in any combination. In yet another embodiment of the present invention, the known method of drying used may be such as air drying, solar drying, steam drying. Detailed description The process of the present invention is described below in detail. The water containing dissolved organics and salt (common salt) is subjected to separation by known method to get water free from undissolved particles. pH of the water is adjusted in the range of 3.0 - 5.3 by known method of addition of acid or alkali and the treated water is subjected to separation by known method. It is then treated with 0.1- 1.0% w/v, of oxidizing agent for 2-4 hours. The resulting water is then passed through 70-80% w/v of activated carbon, characterized by surface area in the range of 220-240 m2/g, and the macropores and mesopores ratios in the range of 1:0.6 and 1:1 for 4-6 hours. Water free from dissolved organics is collected by conventional method and is dried by known method. The resultant dried salt (common salt) can be reused. The inventive step of the present invention lies in the use of oxidizing agent coupled with carbon oxidation using air whereby the free radicals released by the oxidants are trapped by the dissolved organics adosrbed onto activated carbon. The dissolved organics are fragmented by the immobilised microorganisms in the mesopores of activated carbon. The fragemented organics are completely oxidised generating gaseous carbon-di-oxide, that escapes, while the free chloride ions, residing on the particle pheripheraral surface of the pores remain in water itself without coming in contact with the free radicals, thus ensuring that the reaction is not hindered, thereby forming saline water free from dissolved organics. In contrast to the hithertoknown methods where the free radicals generated are scavenged by the chloride ions present in the salt laden water, thereby making the oxidant ineffective, the present invention enables the free radicals to be held over the carbon surface, facilitating chain reaction of breaking down the organic molecules present in the salt laden water containing dissolved organics. The following examples are given by way of illustration only and therefore, should not be construed to limit the scope of the present invention. Example 1 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of water collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interais of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 - 10000 mg/1. pH of the salt laden wastewater was adjusted to 4.0 using IN H2SO4. The resultant water was then filtered using filter paper. 10ml of Fenton's reagent was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 220- 240 m2/g; Bulk density = 0.4-0.8 g/cc. The mesoporous and macroporous ratio of the carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun to get salt. The salt crystals thus obtained after evaporation was found to have 60% purity. Example 2 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 - 10000 mg/1. pH of the salt laden wastewater was adjusted to 4.5 using IN H2SO4. The resultant water was then decanted. 15 ml of Fenton's reagent was added directly to the filtered water with continuous stirring forl0 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash - 50.75 %; Surface area - 220- 240 m2/g; Bulk density = 0.4-0.8 g/cc. The mesoporous and macroporous ratio in the activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker, which was placed on water bath to get steam drying for 6 hours. The salt crystals thus obtained after evaporation was found to have 65% purity. Example 3 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity in terms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 5.3 using IN H2SO4. The resultant water was kept for settling. 20 ml of Fenton's reagent was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 220- 240 m2/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker. Air drying of the water was carried out using drying pans under shadow. The salt crystals thus obtained after evaporation was found to have 70% purity. Example 4 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 4.5 using 1N H2SO4. The resultant water was then filtered using ordinary filter paper. 10 ml of Ozone was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 180-200 m2/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 50% purity. Example 5 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 4.5 using 2N H2SO4. The resultant water was then filtered using ordinary filter paper. 10 ml of Hydrogen peroxide was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 220- 230 m2/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 70% purity. Example 6 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 4.3 using 1N H2SO4. The resultant water was then filtered using ordinary filter paper. 10 ml of Potassium permanganate was added directly to the filtered water with continuous stirring forl0 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 220- 220 m2/g; Bulk density - 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 60% purity Example 7 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 5.0 using 1N H2SO4. The resultant water was then filtered using ordinary filter paper. 20 ml of Potassium permanganate reagent was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 210-240 m2/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon were maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 65% purity. Example 8 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 5.0 using 1N H2SO4. The resultant water was then filtered using ordinary filter paper. 5 ml of Potassium permanganate reagent and 10 ml of ozone was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area 190-220 m/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon were maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 65% purity. Example 9 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 5.0 using 1N H2SO4. The resultant water was then filtered using ordinary filter paper. 10 ml of Fenton's reagent and 5 ml of ozone was added directly to the filtered water with continuous stirring for 10 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 200- 220 m2/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 65% purity. Example 10 Ten liters of salt laden wastewater from a tannery was collected in a plastic container. The chemical properties of wastewater collected was studied as per the method followed in American Public Health Association (2000) and it was estimated as Salinity interms of chloride as 20000 - 40000 mg/1, Biochemical Oxygen Demand (BOD) as 1000-2000 mg/1; Chemical Oxygen Demand (COD) as 3000 - 6000 mg/1; suspended solids as 4000 -10000 mg/1. pH of the salt laden wastewater was adjusted to 5.0 using 1N H2SO4. The resultant water was then filtered using ordinary filter paper. 10 ml of Hydrogen peroxide and 5 ml of ozone was added directly to the filtered water with continuous stirring forl0 minutes and was kept undisturbed for two hours. After a period of 2 hours the supernatant was decanted. A continuous flow reactor of 60 cm height was packed with the activated carbon having the following characteristics; Carbon content = 48.45%; Hydrogen content = 0.7%; Nitrogen content = 0.10%; Ash = 50.75 %; Surface area = 180-220 m2/g; Bulk density = 0.4-0.8 g/cc. The mesopores and macropores of the-activated carbon was maintained between 1:0.6 and 1:1. The bed of the packing was made up to 6cm in diameter and 42 cm height. The decanted water was passed through the reactor column as prepared above at hydraulic retention time of 6 hours. The treated liquor coming out at the outlet of the reactor was collected in beaker and evaporated under sun. The salt crystals thus obtained after evaporation was found to have 65% purity. Advantages The main advantages of the present invention are listed below. 1. Salt obtained from the invention is having > 90% purity 2. Addition of oxidizing agent oxidizes dissolved organics in the salt laden water 3. Residual pollution parameters such as Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Dissolved Solids (TDS) are reduced. 4. Getting salts devoid of colour at a short detention time 5. The salts can be reused for preservation of skin/hide, or for food preservation 6. Clogging of the reactor doesn't take place 7. Maintenance cost of this treatment technique will be comparatively less than the conventional technologies. We claim 1. A process for recovery of salt from salt laden water containing dissolved organics for reusable option which comprises (i) adjusting the pH of the water containing both dissolved organics and salt to 3.0-5.3 by known method, (ii) treating the water, as obtained in step (i) 0.1-1/0% w/v, of known oxidizing agent for a period of 2-4 hours followed by passing the same through 70-80% w/v, of activated carbon having surface area in the range of 220-240 m2/g characterized in that the oxidizing agent coupled with carbon oxidation using air whereby the free radials released by the oxidants are trapped by the dissolved organics absorbed onto activated carbon for a retention period of minimum 6 hours and collecting the resulting water by known method to obtain saline water free from dissolved organics (iii) drying the saline water, as obtained in step (ii) by conventional method to obtain salt (Common salt) for reusable options. 2. A process, as claimed in claim 1, wherein the known method of separation is selected from decanting, filtration, settling. 3. A process, as claimed in claim 2, wherein the activated carbon used for oxidizing dissolved organics is such as rice bran based carbon with surface area in the range of 220-240m2/g, macropore and mesopores in the ratio between 1:0.6 and 1:1. 4. A process, as claimed in claim 3, wherein the oxidizing agent used is selected from potassium permanganate, hydrogen peroxide, ozone, Fenton's reagent, either individually or in any combination. 5. A process, as claimed in claim 4, wherein the known method of drying used is such as air drying, solar drying, steam drying

Documents:

317-del-2004-abstract.pdf

317-DEL-2004-Claims-(08-02-2012).pdf

317-del-2004-claims.pdf

317-DEL-2004-Correspondence Others-(08-02-2012).pdf

317-DEL-2004-Correspondence Others-(15-11-2011).pdf

317-del-2004-correspondence-others.pdf

317-del-2004-correspondence-po.pdf

317-del-2004-description (complete).pdf

317-del-2004-form-1.pdf

317-del-2004-form-18.pdf

317-del-2004-form-2.pdf

317-del-2004-form-3.pdf

317-del-2004-form-5.pdf