Title of Invention	PROCESS FOR TREATMENT OF ALUM CONTAINING CLARIFIER SLUDGE
Abstract	A process for treatment of metal hydroxides containing alum sludge generated by clarification processes is disclosed. The process involves mixing of porous ion exchange resin with the alum sludge to recover aluminium ions for reconstituting the alum and thereby recycling the alum used in the process and reducing the loss of alum from water treatment plants. 9 JUN 2008

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FORM -2 THE PATENT ACT, 1970 (39 of 1970) & THE PATENT RULES, 2003 COMPLETE SPECIFICATION (See section 10 and Rule 13) TREATMENT OF ALUM SLUDGE THERMAX LIMITED an Indian Company of D-13, MIDC Industrial Area, R.D. Aga Road, Chinchwad, Pune-411 019, Maharashtra, India. THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. FIELD OF THE INVENTION The present invention relates to a process for treatment of alum sludge from clarifier. BACKGROUND Definitions In the context of this invention the term 'alum' includes mineral acid salts such as chloride or sulfate salts of metals which include alkali metals (Na, K alkaline earth metals (Ca, Mg), aluminum and iron. "Eluent" means an acidic solvent used in the process of eluting adsorbed metals ions from ion exchange resins; "Eluate" means an acidic solution containing separated metal ions from the ion exchange resin obtained after elution. "Bed volume" [BV] means the volume of eluent or wash water used per unit volume of the resin in the bed. "Chamber" in the context of the present invention means a bed, a container, a vessel or a column wherein the method step of elution is carried out. Introduction Water being the cheapest and easily available universal solvent, is used in numerous industries. Raw water is derived from sources such as river, lakes and underground. While, underground water is clear due to natural filtration; the surface water contains suspended impurities such as silt, mud, humic acids etc. The suspended solids in surface water vary from as low as 20 ppm to as high as 10,000 in rivers during rains. 2 Before industrialization, water was available as a free abundant source because of less contamination. With the increased use of water by the expanding population and growing industries, waste water discharge and resulting pollution from it has become a cause of concern. In the developing world, wastewater still goes untreated into local rivers and streams. The untreated water disposal not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources. Hence, positive action to reduce and eliminate water contamination is needed. The effluent water after biological or chemical treatment is clarified. Water treatment is a process used to make water more acceptable for a desired end-use and to allow treated water to discharge into the environment without adverse ecological impact. These processes may be physical such as settling, chemical such as disinfection or coagulation or biological such as lagooning, slow sand filtration or activated sludge. Clarifier is a structure usually in the form of a tank or a basin, for separating sludge from clearer waste water in a typical water treatment plant. Clarifier is designed to coagulate, flocculate and settle the suspended impurities from the raw as well as the secondary effluent. The settled sludge from clarifier is further thickened and disposed. A continuing demand exists for reduction in the sludge generated from water and waste water clarifiers. The suspended impurities vary from 50 ppm to 1000 ppm or more depending on the treatment given before clarification. The suspended solids in water have size in submicrons and hence as per stokes law, a long time is taken to settle this matter. Further, few particles known as 3 colloids are charged with -ve electric potential and the particles repel each other preventing their precipitation. Hence to ensure their sedimentation in reasonable time; coagulation is done to neutralize the change and bring the colloids to gather followed by flocculation to make a larger size particle for faster settling. Various flocculating agents are used in domestic and industrial clarification processes. Alum is one of the most widely used and inexpensive flocculating agent. A primary coagulant such as polyDADMAC and flocculants such as Polyacrylamide are also widely known. However, these synthetic polymers are many a times cost prohibitive. Generally, alums are used in the range of 5 to 1000 ppm as flocculants to remove suspended impurities. Flocculating agents are generally metal salts which undergo reaction when used in water to form poly-hydroxy insoluble complex which have positive charges to neutralize negative charges on colloids and their polymeric nature helps to form large floes. Commonly used flocculating agents are prepared from aluminium and iron as chloride and sulphate salts. A combination with many alkali and alkaline earth metals such as Na, K or Ca, Mg are used to optimize flocculating Action. Alum is used in various forms such as solid, liquid as a solution, partially neutralized form, pre polymerized form like Poly aluminum chloride and various combinations with caustic, lime and other aids. The coagulated colloids are flocculated further with alum or polyelectrolytes to make larger floes for sedimentation. A clarifier system is designed to coagulate, flocculate and settle suspended impurities from raw as well as 4 secondary effluent. Thus alum end up in the sludge along with other suspended matter from water. Depending upon the inlet turbidity and when alum is used as flocculating agent, metals hydroxide, contribute to 30 to 90 % by volume of the total sludge produced from a clarifier. The sludge from a clarifier is concentrated in thickeners and further dried for disposal as land filling. The disposal of clarifier sludge in a landfill results in the loss of a valuable asset (metal ions) and the metal hydroxides in the sludge causes ground water contamination which is an environmental issue. The dewatering and disposal of Clarifier sludge adds significantly to the cost of treating water because the generated sludge is difficult to dry and dispose due to voluminous and gelatinous nature of metal hydroxides. Further, the clarifier sludge has unacceptable color, especially when iron based flocculating agents are used. Hence from economic, aesthetic and environment point of view, reduction of metal in the sludge is sought by users. Ion exchange processes generally involve reversible chemical reactions between solid ion exchangers and an aqueous solution whereby ions are interchanged between the exchanger and the solution. The most widely used exchangers are ion exchange resins which comprise, for the most part, insoluble organic polymer matrices having attached functional groups which provide mobile ions which may be exchanged for ions in the solution bearing the same charge. To impart increased stability to the resins, the matrices are usually prepared by addition copolymerization reactions which provide varying degrees of cross linking. Depending upon the nature of the functional group, ion exchange resins are classified broadly as strong acid, weak acid, 5 strong base and weak base. The acid exchange resins are further classified as cation exchangers while the Base Exchange resins are usually referred to as anion exchangers. Strong acid cation exchange resins typically comprise sulfonated copolymerized styrene-divinylbenzene products crosslinked to varying degrees. Such resins are widely used in water conditioning, demineralization of syrups, chromatographic separations, and metal recovery. Weak acid cation exchange resins are commonly prepared by reacting an unsaturated carboxylic acid, e.g., acrylic or methacrylic acid, with a crosslinking agent such as divinylbenzene or ethylene glycol dimethacrylate. Functional groups may comprise phenolic, phosphorous or carboxylic entities, combinations of these and others. Weak acid resins have found application in water conditioning, chromatographic separation, and metal recovery. Strong base anion exchange resins generally are prepared by affixing quaternary ammonium groups to a polystyrene divinylbenzene matrix. Resins of this type are used principally in water conditioning. Weak base anion exchange resins contain primary, secondary and tertiary amine groups or mixtures of such groups. Such resins are available in a variety of types including condensation products of amines with formaldehyde, alkyl dihalides, chloromethylated styrene-divinylbenzene, and the like. Existing Knowledge The process of removal of metal from water in dissolved form using Ion exchange resins is widely applied commercially, for example, the removal of 6 iron from pickling bath wash is widely done by using Ion exchange resins. The use of ion exchange resins for metal removals is also commercially used in mineral extraction. Gold, uranium extraction is done commercially by use of Ion exchange resins. The demineralization process also removes all metal impurities in water on cation exchange resins. It is well known that metal ion especially polyvalent metal ions such as Iron and aluminum have higher affinity for resins. The details regarding the recycling of the metal hydroxide by an extraction process with acids; the problem associated with the disposal of alum sludge, the possible contamination of ground water and alternative uses of sludge in cement, soil stabilization have been provided in "Integrated design and operation of water treatment facilities" by Susumu Kawamura . Furthermore, the problem of disposal of alum sludge, & methods of disposal are also disclosed in an article title "A Study of the Alum Sludge's from Cali City Water Treatment Plants" published in Vol 26, No.2, May , 1999 of AWWA,. US Patent number 3,959,133 discloses a process of recovering alum from sludge obtained from settling basins which involves lowering the pH of the sludge by addition of Sulfuric acid in proportionate amount to the thickened sludge for stabilizing the metal ion in metal hydroxide precipitate. The dissolved aluminum, in the form of aluminum sulfate (liquid alum), is separated from the residual solids by a gravity separator and returned to storage for reuse while the residual sludge is disposed. The aforesaid acid process as disclosed in US,Patent number 3,959,133 presents a potentially serious problem in that it is vulnerable to the accumulation of certain 7 impurities in the recovered alum. If this occurs, and the recovered alum is used for water treatment, it may cause a degradation of the potable water. US Patent number 5,304,309 discloses continuous cyclic process which employs a weak acid chelating exchanger in the form of a composite membrane for selective coagulant recovery from clarifier sludge in water treatment plants. However, composite ion exchange materials are not available in sizes appropriate for large scale applications and the process is not capable of concentrating alum to high levels. US Patent number 6,495,047 discloses a process that selectively recovers alum from sludge to reduce the volume of the disposable solids wherein a cation exchange membrane comprising plurality of sheets arranged in stacks is used. Though the process involves recovery of the coagulant compound which is a ferric compound, the process suffers from several drawback generally associated with the use of membranes. OBJECTS OF THE INVENTION It is an object of the present invention to provide a process for treatment of Alum sludge from clarifiers by resins. Another object of this invention is to provide a cost effective and economically feasible process of recovering and recycling alum from clarifier sludge. 8 Yet another object of this invention is to provide a process of treatment of alum sludge which reduces the clarifier sludge volume thereby making its disposal economical. Still another object of this invention is to provide a process of treatment of alum sludge wherein the metal content in sludge is reduced thereby making its disposal environment friendly. Still further object of this invention is to provide a process of treatment alum sludge from clarifier which reduces the wastage of alum to landfills. A further object of this invention is to provide a process of treatment of alum sludge wherein the resin is reused by regeneration. SUMMARY OF THE INVENTION A process for treatment of metal-containing clarifier sludge comprising the following steps: mixing said sludge with an ion exchange resin to form a mixture; packing the mixture in a chamber; washing the mixture with a washing agent in the chamber to remove non-metallic components therefrom, while the rest of the sludge being adsorbed on the ion exchange resin, to result in a washed mixture resident in the chamber; treating the washed mixture in the chamber with an acid-eluent in a controlled manner to collect a first eluate whilst BV/hr flow rate through the chamber is in between 2 to 6; 9 collecting a second eluate whilst BV/hr flow rate through the chamber is greater than 4; recycling the second eluate as the acid-eluent to the chamber solely or in combination with fresh acid-eluent in method step d; constituting the alum from the first eluate; and recovering the ion exchange resin and optionally defouling the ion exchange resin before reuse. Typically, the ion exchange resin is a cationic exchange resin. The cationic exchange resin is selected from a group of cationic exchange resins consisting of strong acidic, styrenic and acrylic. Preferably, the cationic exchange resin is in the form selected from a group of forms consisting of macro-porous, gel, beads, aero-gel, chips and semi-solid. In accordance with one preferred embodiment of the invention, the cationic exchange resin is in the form of a gel. In accordance with another preferred embodiment of the invention, cationic exchange resin is in the macro-porous form. Typically, the quantity of strongly acidic cation exchange resin is in the range of about 0.9 to 5 times the equivalent adsorption capacity of the resin. Preferably, the quantity of strongly acidic cation exchange resin is in the range of about 1 to 2 times the equivalent adsorption capacity of the resin. Typically, the washing agent is water. 10 Typically, during the method step of washing, volume of the washing agent in the chamber is subjected to expansion in the range of about 40% to 60 %. Typically, the eluent is at least one eluent selected from a group of eluents consisting of sulfuric acid and hydrochloric acid. Typically, the concentration of the eluent is in the range of about 4 to 15 %. Preferably, the first eluate is collected while maintaining BV/hr flow in the range of 2 to 4. Typically, the process of defouling of the ion exchange resin comprises passing 5 to 15 % alkaline brine, preferably, 10% sodium chloride with 0.1 to 0.5% caustic at 1 to 5 BV/hr flow through the resin column. Alternately, the process defouling of the ion exchange resin comprises soaking the ion exchange resin in 5 to 15 % alkaline brine, preferably 10% sodium chloride with 0.1 to 0.5%) caustic. DETAILED DESCRIPTION OF THE INVENTION Accordingly, there is provided a method for treatment of metal hydroxide containing clarifier sludge by mixing Ion exchange resin in appropriate form and proportion with sludge to adsorb the metal ion from sludge. The present invention provides a process that removes metal ions from the clarifier sludge 11 making disposal of sludge easy and recovers the metal ions for reconstituting the alum and thereby recycling the alum used. In accordance with this invention there is provided a process for treatment of metal- containing clarifier sludge comprising the following steps: a) mixing said sludge with ion exchange resin to form a mixture; The mixing is carried out under continuous stirring for the period of 1 to 6 hrs, preferably for 2 to 4 hrs so as to keep resin under suspension. The resin preferably absorbs the metallic ions such as iron, aluminium from the sludge. The sludge after the treatment with resin contains substantially reduced volume of metal salts and can be disposed after conventional treatment. b) packing the mixture in a chamber. Mixture prepared in step a) is then introduced in a chamber. Depending on the scale of operation a chamber can be a bed, a column or a vessel. c) washing the mixture with a washing agent in the chamber to remove non- metallic components therefrom, while the rest of the sludge being adsorbed on the ion exchange resin, to result in a washed mixture resident in the chamber. Typically, the backwash is given for 10 to 60 minutes; more preferably for 15 to 25 minutes at flow rate of 4 BV to 20 BV per hr. Preferred flow rate is to maintain the volume of the washing agent to 40 to 60 % of the capacity of the chamber. d) treating the washed mixture in the chamber with an acid-eluent in a controlled manner to collect a first eluate whilst BV/hr flow rate through the chamber is in between 2 to 6. 12 Typically, the present invention uses dilute acids for regeneration which are available as byproducts from many plants at much lower costs making this process more cost effective. Typically, the first eluate contains salts of metal such as aluminum or iron chloride or sulphate, depending on the particular acid used (sulphuric or hydrochloric) and excess acid. The respective alum is recovered from the said first eluate. The concentration of metal salts in the recovered alum varies with: • concentration and quantity of acid used for elution and • cut off point for metal recovery which is optimized depending on the cost. The concentration of the acid is also decided on the alkalinity of the water to be treated. Higher acid concentration is acceptable when water alkalinity is higher. e) collecting a second eluate whilst BV/hr flow rate through the chamber is greater than 4. f) recycling the second eluate as the acid-eluent to the chamber solely or in combination with fresh acid-eluent, in method step d. g) constituting the alum from the first eluate. In accordance one preferred embodiment of the invention, first eluate as such is used as flocculating agent or alum. In accordance with another preferred embodiment of the invention, the reconstitution of the alum recovered in the first eluate is done by partial neutralization of excess acid by adding an alkaline agent selected from a group consisting of caustic, lime, aluminum hydroxide and iron hydroxide. Preferably, caustic or lime is used for partial neutralization. 13 h) recovering the ion exchange resin and optionally defouling the ion exchange resin before reuse. The resin after elution and draining of excess acid is directly used for the next metal adsorption cycle thereby obviating the need for wash water treatment. Typically, the ion exchange resin is a cationic exchange resin. Typically, the cationic exchange resin is selected from a group of cationic exchange resins consisting of strong acidic, styrenic and acrylic. Typically, the strongly acidic cation exchange resin is selected from hydrogen, sodium or Calcium form preferably in Hydrogen form with functional group sulphonic, phosponic, carboxylic or chelating. More preferably the functional group is sulphonic group. The Cation resin can also be styrenic or acrylic, preferably styrenic; macro porous or gel preferably macro porous with surface area from 15 to 35 sqm/gm; preferably 25 sqm/gm. Typically, the resin used in the present invention for metal absorption is cation, more preferably strongly acidic macroporous cation. The cross linked resin with degree of cross-linking between 4 to 16% and surface area in the range of 0 to 35 Sqm/gm can also be used which is selected depending on the nature of organic components of the sludge. Typically, the cation exchange resin is in the form selected from a group of forms consisting of macro-porous and gel. In accordance with one preferred embodiment of the invention, the cation exchange resin is in the form of a gel. In accordance with another preferred embodiment of the invention cation exchange resin is in the macro-porous form. 14 Typically, the quantity of strongly acidic cation exchange resin is in the range of about 0.9 to 5 times the equivalent adsorption capacity of the resin. Preferably, the quantity of strongly acidic cation exchange resin is in the range of about 1 to 2 times the equivalent adsorption capacity of the resin. Typically, the washing agent is water. Typically, during the method step of washing, preferably the flow rate is maintained so as to retain the washing agent in the chamber occupying 40 to 60 %, preferably 50 % of the capacity of the chamber. Typically, the eluent is at least one eluent selected from a group of eluents consisting of sulfuric acid and hydrochloric acid. In accordance with one preferred embodiment of the invention, the eluent is hydrochloric acid. Typically, the concentration of the eluent is in the range of about 4 to 15%. Preferably, the first eluate is collected while maintaining BV/hr flow in the range of 2 to 4. In accordance with this invention there is also provided a process for removal of any foulants present on the resin due to organics or anionic organics which is carried in the following manner. Typically, the process of defouling of the ion exchange resin comprises passing 5 to 15 % alkaline brine, preferably 10% sodium chloride with 0.1 to 0.5%o caustic at 1 to 5 BV/hr flow through the resin column; Alternately, the process defouling of the ion exchange resin comprises soaking the ion exchange resin in 5 to 15 % alkaline brine, preferably 10% sodium chloride with 0.1 to 0.5% caustic. 15 TECHNICAL ADVANCEMENT The process as described herein above offers several advancements over processes disclosed in the prior art in terms of overall simplicity and the recoverability of almost all the reagents. Furthermore, the process reduces the metal content of the clarifier sludge thereby reducing its volume which in turn helps in easy disposal. In case of iron containing flocculating agents, the process also helps in discoloration of the disposable sludge thereby improving its acceptability for land filling purposes. Regenerability of the ion exchange resin aided with its defouling ensures repeated use of the resin to its fullest extents for significantly longer periods of time. Similarly, recycle of alum constitutes the most significant feature of the process for it renders the process environment friendly and saves the valuable alum. ECONOMIC SIGNIFICANCE Approximate quantity of Alum used in a plant of 1 million liters per day capacity is 50 kgs/day. By using the process in accordance with this invention almost 80 % of the alum can be recovered. Thus in a plant of aforesaid capacity almost 40kg of the alum can be recovered. Apart from the savings in terms requirement of alum per day, another economically significant aspect is that by using the process in accordance with this invention, there will be almost 80% reduction in the quantity of alum that goes with sludge. Furthermore, the process of treatment of alum sludge in accordance with this invention reduces the clarifier sludge volume thereby making its disposal economical. 16 The invention will now be described with respect to the following examples which do not limit the invention in any way and only exemplify the invention. Example 1 310 ml of strongly acidic cation Tulsion T 42 in Hydrogen form was mixed with 500 ml of sludge containing 1% aluminium. The mixture was stirred for 3 hrs. The mixture was then taken in a 25 mm chamber and backwashed to remove balance sludge at 4 BV flow rate. The backwash water was collected in a beaker and allowed to settle to measure the sludge volume. The volume of the sludge in the backwash was 50 ml about 1/10th of the original sludge volume. The sludge was collected and was analyzed by standard methods for aluminium and the percentage of aluminium was found to be less than 0.12% i.e. about 88% reduction. Example 2 310 ml of strongly acidic cation resin Tulsion T 42 having 8% cross-linking was mixed with 500 ml of sludge containing 1% aluminium. The mixture was stirred for 2 hours in a beaker. The mixture was then taken in a 25 mm column. The resin was then backwashed with demineralized water to remove remaining sludge. The sludge was collected and was analyzed by standard methods for aluminium absorption over resin. The analysis shows that 82% of the aluminium in the sludge was absorbed on the resin. 17 Example 3 370 ml of strongly acidic cation resin Tulsion T 42 having 8% cross-linking was mixed with 500 ml of sludge containing 1% aluminium. The mixture was stirred for 2 hours in a beaker. The mixture was then taken in a 25 mm column. The resin was then backwashed with demineralized water to remove remaining sludge. The sludge was collected and was analyzed by standard methods for aluminum absorption over resin. The analysis shows that 85% of the aluminium in the sludge was absorbed on the resin. Example 4 470 ml of strongly acidic cation resin Tulsion T 42 having 8% cross-linking was mixed with 500 ml of sludge containing 1% aluminium. The mixture was stirred for 2 hours in a beaker. The mixture was then taken in a 25 mm chamber. The resin was then backwashed with demineralized water to remove remaining sludge. The sludge was collected and was analyzed by standard methods for aluminium absorption over resin. The analysis showed that 87% of the aluminium in the sludge was absorbed on the resin. Example 5 The absorption of the metal ion on the resin was done by mixing ion exchange resin with large quantity of sludge as described in the example 1. Then water 18 backwash was given for 15 min. to remove any particulate matter to get the 50% bed expansion. After settling the resin, the excess water was drained. After removal of non-metallic impurities and particulate matter from resin, by washing, the said resin was treated with an acid eluent, 6% Hydrochloric acid (HC1), 8 times the volume of resin at 4BV flow rate in resin column. The resin was analyzed by standard methods for aluminium absorption. The analysis showed that the 90% of the aluminium was desorbed from the resin. The different fractions of eluates were collected in two distinct lots at different BV flow rates. First Eluate containing high metal concentration Fraction with 12.4 % alum was collected first. Cut off point for first eluate was at the B V rate of 4. Subsequently, second eluate containing low metal concentration fraction with balance alum was collected at higher BV flow rates. The collected eluate lots were analyzed for aluminium and results are as shown in the Table 1 below. Table 1: BVof 0 1 2 3 4 5 6 7 8 acid passed %A1 0 40 63 76 80 85 87 89 90 recovered Example 6 The resin regenerated as described in example 5 was used after backwash. First three fractions of resin were collected by which 76% of metal salt was recovered. The resultant mixture of three fractions contains 12.4% alum and 19 4.4% of acid. The coagulation tests were done by jar test apparatus and results were similar when compared with fresh 12.4% alum solution under similar conditions. 1 Initial turbidity of water: 730 NTU 2 Alum (Al2 (S04)3, 18 H20) dose =150 ppm 3 Turbidity of water after flocculation with fresh alum = 3 NTU 4 Turbidity of water after flocculation with 80% recycle alum = 10 NTU 5 Turbidity of water after flocculation with 80%> recycle alum and adjusting pH with lime to original water pH = 2 NTU Example 7 The fractions of eluate from 4 to 8 [second lot of eluate with low metal concentration] as given in example 5, were reused as an eluent. The cation exchange resin loaded with metal was treated with the second lot of eluate and backwashed with demineralized water as described in example 2. The analysis of the collected alum fractions are given in the table 2 below: Table 2: Fraction 0 4 5 6 7 8 1 2 . 3 Passed %A1 0 40 63 76 80 85 87 89 90 recovered 20 1, 2 and 3 were the fractions of fresh acids. Based on this analysis, present invention recommends optimization of concentration of acid and recycle of excess acid fractions based on the cost and alkalinity of water. Foulants present on the resin due to organics or anionic organics were removed by passing 10% sodium chloride with O.4% caustic at 1 BV flow. In one of the adsorption cycles, the defoulants on the ion exchange resins were removed by soaking the resin in 10% sodium chloride withO.4% caustic for 2 hrs to remove the organic foulants. Example 8 The details of sludge from a municipal plant were as per the details given below: A) The quantity & quality of sludge generated is as given below Quantity: 1) Sludge : 19 cum/day 2) Alum: 150Kgs/day Sludge Analysis: 1) Total Solids: 3.64% 2) Total dissolved solids: 150 mg/1. 3) Average Aluminum contents as Al: 0.064 %. Sludge was treated with conventional method and disposed off to land.. B) Results 1) The original volume of sludge taken for treatment with invented process = 1100 ml 2) Volume of final sludge after using invented process = 400 ml 21 3) Reduction in sludge volume by invented process = 63% 4) Metal contents in the original sludge = 0.64 gpl 5) Reduction in Metal contents in the sludge by invented process = 95.3 % 6) Quantity of flocculating agent saved = 80 % 8) Quantity of acid required/ kg of flocculating agent substituted by recycle = 5.62kgs of 30% HCl 9) Quantity of lime (80% purity ) required to maintain alkalinity of water per kg of alum saved = 1.25 Kgs. While considerable emphasis has been placed herein on the specific steps of the preferred process, it will be appreciated that many steps can be made and that many changes can be made in the preferred steps without departing from the principles of the invention. These and other changes in the preferred steps of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. 22 We Claim 1. A process for treatment of metal-containing clarifier sludge comprising the following steps : a. mixing said sludge with an ion exchange resin to form a mixture; b. packing the mixture in a chamber; c. washing the mixture with a washing agent in the chamber to remove non-metallic components therefrom, while the rest of the sludge being adsorbed on the ion exchange resin, to result in a washed mixture resident in the chamber; d. treating the washed mixture in the chamber with an acid-eluent in a controlled manner to collect a first eluate whilst BV/hr flow rate through the chamber is in between 2 to 6; e. collecting a second eluate whilst BV/hr flow rate through the chamber is greater than 4; f. recycling the second eluate as the acid-eluent to the chamber solely or in combination with fresh acid-eluent in method step d; g. constituting the alum from the first eluate; and h. recovering the ion exchange resin and optionally defouling the ion exchange resin before reuse. 2. A process as claimed in Claim 1, wherein the ion exchange resin is a cationic exchange resin. 3. A process as claimed in claim 2, wherein the cationic exchange resin is selected from a group of cationic exchange resins consisting of strong or weak acidic, styrenic and acrylic. 23 4. A process as claimed in claim 3, wherein the cationic exchange resin is in the form selected from a group of forms consisting of macro-porous, gel, beads, aero-gel, chips and semi-solid. 5. A process as claimed in claim 4, wherein the cationic exchange resin is in the form of a gel. 6. A process as claimed in claim 4, wherein cationic exchange resin is in the macro-porous form. 7. A process as claimed in claim 1 and 3, wherein the quantity of strongly acidic cation exchange resin is in the range of about 0.9 to 5 times the equivalent adsorption capacity of the resin. 8. A process as claimed in claim 6, wherein the quantity of strongly acidic cation exchange resin is in the range of about 1 to 2 times the equivalent adsorption capacity of the resin. 9. A process as claimed in claim 1, wherein the washing agent is water. 10. A process as claimed in claim 1, wherein during the method step of washing, volume of the washing agent in the chamber is subjected to expansion in the range of about 40% to 60 %. 24 11. A process as claimed in claim 1, wherein the eluent is at least one eluent selected from a group of eluents consisting of sulfuric acid and hydrochloric acid. 12. A process as claimed in claim 12, wherein the concentration of the eluent is in the range of about 4 to 15%. 13. A process as claimed in claim 1, wherein the first eluate is collected while maintaining BV/hr flow in the range of 2 to 4. 14. A process as claimed in claim 1, wherein the process of defouling of the ion exchange resin comprises passing 5 to 15 % alkaline brine, 10% sodium chloride with 0.1 to 0.5%) caustic at 1 to 5 BV/hr flow through the resin column; 15. A process as claimed in claim 1, wherein the process defouling of the ion exchange resin comprises soaking the ion exchange resin in 5 to 15 % alkaline brine, 10% sodium chloride with 0.1 to 0.5% caustic. Dated this 9th day of June, 2008 Mohan Dewan of R. K. Dewan&Co Applicants' Patent Attorneys 25

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