Title of Invention

IMPROVED BIO-CHEMICAL PROCESS FOR CONVERSION OF NITROGENOUS COMPOUND PRESENT IN WASTE WATER

Abstract

A biochemical process for conversion of nitrogenous compound present in the waste water from coke oven consisting of ammoniacal nitrogen, cyanide and thiocyanate. The waste water is treated to remove sludge. It is then subjected to biodegradation reaction in bioreactors in the presence of bacteria to effect a nitrification reaction. The flow of the waste water is controlled in order to maximize the nitrification reaction and the rate of air supply into the bioreactors is also controlled. The treatment is carried out under a pH of between 7-9 to effect optimum nitrification of the nitrogenous compounds present in waste water. The process is affected in a device in which the waste water from the coke oven is stored in a few tank. The waste water is cooled at room temperature and fed to a plurality of biodegradation tanks connected in series through clarifiers, said biodegradation tankers having aeration assembly fixed inside. Means are provided for feeding the waste water to the biodegradable tankers at a predetermined level.

Full Text

The present invention relates to a biochemical process for the conversion of nitrogenous, compounds present in industrial waste slurry into nitrate form and also to an installation for carrying out the said process. The invention more specifically relates to the treatment of waste water obtained from coke oven batteries. Waste water from coke oven batteries mainly contain nitrogenous compounds in the form of ammoniacal nitrogen, thiocynates, cyanides etc along with small quantity of phenol and other miscellaneous organic compounds in traces which results from the coal carbonization process, amount of which slightly varies depending on the temperature of carbonization. Disposal of waste slurry including waste water containing several poisonous chemicals which if disposed without treatment will create serious problems to the environment. The Pollution Control Board has therefore made-mandatory for industries either small or large to have waste treatment plants. The most commonly observed nitrogenous compound present in coke oven waste water are ammoniacal nitrogen, cyanide and thiocyanate. The levels at which these are usually found in waste water from coke batteries is as follows : Compounds mg/litre Ammoniacal nitrogen - 400 - 600 Cyanide - 20-50 Thiocyanate - 150 - 250 Additionally other materials that are found in small amounts are aromatic hydrocarbons including phenols.. Removal of phenol and other organic compounds can be easily done by using conventional methods e.g., aeration but the main problems centers around the removal of the nitrogenous compounds. 2 Biodegradation of nitrates nitrogen into N2 is a conventional process known in the art. The process of nitrification (producing nitrate N2) preceeds denitrification and subsequent removal of nitrogen compound through N2 gas. The conventional methods of the waste water treatment from coke battery are much above the parameters prescribed by the Pollution Control Board. As a result the different control parameters for nitrification reaction assumes significant importance. As biodegrardation to N2 was the ultimate goal, inventors made detailed study on factors controlling nitrification (conversion into nitrate) reaction specific and suitable for coke oven waste water containing significant quantities of various nitrogen bearing chemicals. These chemicals contribute to environmental pollution. The known methods for the removal of ammoniacal nitrogen cannot meet the requirement of the Pollution Control Board. It is therefore the principal object of the present invention to provide an improved process to convert the ammoniacal nitrogen and other common nitrogen containing components present in coke oven waste water into nitrates. Another object of the present invention is to avoid atmospheric pollution from waste water containing nitrogenous compound, discharged from coke oven batteries. A further object of the invention is to develop a process in which ammoniacal N2 and other forms of N2 can be easily converted into nitrates for assimilation and growth of denitrifying bacteria. A still further object of the invention is to identify, develop and further optimize the controlling factors leading to maximum yield of nitrate in coke oven waste water. 3 The inventors have found that the conversion of other forms of Nitrogen into nitrate nitrogen depend on several factors. It has been particularly found that the conditions of bacteria control and its growth to form nitrates associated with feed rate of influent waste water in the bioreactor, its pH control and on thiocyanate load of waste water are critical for effecting the process of the invention. Thus the present invention relates to an improved biochemical process for conversion of nitrogenous compound present in the waste water for coke oven comprising treating the waste water so as to remove sludge ; subjecting the waste water to biodegradation reaction in bioreactors in the presence of bacteria to effect a nitrification reaction, controlling the flow of the waste water in order to maximize the nitrification reaction and controlling the rate of air supply into the bioreactors ; and providing a pH of between 7-9 to effect optimum nitrification of the nitrogenous compounds present in waste water. The bacteria used for the biodegradation reaction is chosen from acclamatized bacteria present in BOD plants. The pH of the mass is controlled by the addition of alkali and alkaline earth components which are selected from sodium carbonate, sodium hydroxide and calcium hydroxide. The waste water before the treatment with bacteria is subjected to room temperature cooling. The invention also provides an installation for carrying out the process according to the invention comprising 4 a feed tank in which the waste water from the coke oven is stored ; cooling means for cooling the waste water to substantially room temperature ; a plurality of biodegradation tankers connected in series through clarifiers, said biodegradation tankers having aeration assembly fixed inside ; means for feeding the waste water to the biodegradable tankers at a predetermined level. The invention will now be described with respect to typical example for a better understanding of the invention and also with reference to accompanying drawings in which Fig. 1 shows a bioreactor with aeration assembly In fig. 1 the assembly consists of feed tank 1, Bio degradation tank (2,4), clarifiers (3,5), aeration assembly (A). All are connected as shown in the drawing. In the present biodegradation reaction for getting an optimum concentration of nitrate to the extent of 80 to 90% from ammoniacal Nitrogen, Cyanide and thiocyanate present in coke oven waste water, an assembly of feed tank (1) is connected to multiple of Bio degradation tanks (2,4) through clarifier (3,5) aeration assembly (A) having ceramic diffuser or mechanical rotating agitator are fitted inside the BOD tanks for air supply. In the present biodegradation reaction an assembly of feed tank 1 (60 L capacity), aeration tank (30 Ltr, two chembers) were connected through intervening clarifier for sludge removal (see fig.). In the last stage 4 Nos. of tall bioreactors (6,7,8,9) (also called BOD tanks) (20 Ltr. Capacity) were connected in series. The four bioreactors (6,7,8,9) carry out the sequential bioreactor 5 reaction through variation in amount of bacteria (MLSS) pH variation which has profound influence on the removal efficiencies of different pollutants. These bioreactors were fitted with mechanical stirrers to avoid sludge settling. Plurality of BOD tanks (2,4) are connected in series through clarifiers (3,5) for removal of excess sludge. Aeration assembly having ceramic diffuser or mechanical rotating agitators are fitted inside the BOD tanks for air supply. Coke oven waste water is fed in the BOD tanks at a predetermined rate after cooling in primary coolers where the waste water to room temperature before entering in BOD plant. In actual bioreactor operation the following operations were carried out sequentially (1) Filling up of feed tank (60 ltr) with coke oven raw waste water everyday. (2) Controlling the pH of the waste water at various levels as required for optimization. (3) Controlling the feed rate from tank A to tank B by adjustment of operating knob to find out the flow rate (ml/hr). (4) Removal of excess sludge in clarifiers and sending back to bioreactors as shown by arrow. (5) Control of air supply into the bioreactors through air pumps (10-15 /hrs.). (6) Measurement of pH, nitrate nitrogen, ammoniacal nitrogen, thiocynate and Cyanide through standard method of analysis. (7) Recording the data and analyzing the same. 6 Certain experimental results demonstrates the content of ammoniacal nitrogen, nitrate and thiocyanide in the final product. Experiments were carried out with original sample containing 400-600 mg/litre ammoniacal nitrogen, cyanide 20-50 mg/litre and thiocynate 150-250 mg/litre and the following results obtained : TABLE I No. of Observations PH Ammoniacal Nitrogen in tank Nitrate - Nitrogen Thyiocynate RE Tank D RE Tank D RE TankD RE TankD 1 7.2 8.1 70.3 50 100 100 5.2 4 2 7.1 8.1 154 64 0 111 7.0 3.2 3 7.0 8.0 104 56 0 185 12.9 4.2 4 7.2 8.2 70 52 0 92 15 12 5 6.9 8.0 - - 0 141 17 14 6 6.9 7.2 138 31 0 88 72 3.2 7 7.0 7.5 124 96 0 56 80 15.2 8 6.0 8.0 - - 0 358 77 9.3 9 7 6 - - 0 24 80 7.8 10 6.5 8.5 84 78 0 294 55.4 1.4 11 6.0 9.6 - - 0 214 10.3 4.2 12 7.8 7.2 - - 0 53 70.5 15.2 13 7.7 7.0 - - 0 14 45.4 5.8 14 7.6 7.2 114 88 0 32 41.7 5.7 15 7.2 7.0 112 78 0 56 41.5 7.1 16 7.7 7.2 178 66 0 36 56.2 3.9 17 7.8 7.6 125 52 0 32 42.3 7.1 18 7.4 7.3 148 80 0 30 6.6 6.0 19 7.8 6.8 272 48 0 24 40.3 16.1 20 7.4 7.0 56 31.6 0 51 18.3 13.5 21 6.9 7.1 93.2 76.8 0 24 16.5 7 22 - - 216 208 0 24 15.3 5.4 23 7.5 6.9 58 13 0 33 12.1 10.8 24 7.5 7.1 216 184 0 17 30.9 9.6 25 6.7 7.0 272 148 0 64 40.3 16.6 7 TABLE 2 Influence of flow rate of Feed to BOD for conversion into nitrate Flow Rate of the feed in BOD Percentage conversion into nitrate i) 8 to l/hr 70% - 80% ii) 4to7 l/hr 85%-90% iii) 3 l/hr 70%-72% TABLE 3 Influence of Thiocvanate content of the feed on percentage conversion to nitrate Theocynate content of Percentage conversion into nitrate the original sample i) 5%-20% 4%- 15% ii) 40% - 80% 85% - 95% From the above results it is clear that (a) Feed rate of raw waste water influence the formation of Nitrate nitrogen in bioreactor and when the feed rate is between 4 to 7 litre per hour the conversion to nitrate is maximum. (b) Similarly pH control of the bioreactor has got a profound influence on the formation of nitrate and at pH between 7 to 9 the formation of nitrate is maximum. (c) Thiocynate content of the feed waste water has got a definite influence on the formation of nitrate and when thiocynate of the feed is below 30 to 40 8 mg/litre it has got practically no influence on the formation of nitrate but when it exceeds the limit, nitrate formation increases. ADVANTAGE The key features of the process of the invention are as under : 1) Establishment of an optimum pH between 7-9 which has found to give optimum nitrification reaction under the existing operating condition. 2) Control of flowrate between 4-7 l/hrs maximizes the nitrification reaction. 3) That the effect of thiocynate level having significant amount has shown and optimum level below 30-40 mg/ltr. Has no affect of on nitrification. Once this load in exceeded then the biodegradation of thyocynate results in additional ammonical nitrogen release influencing ammonia load in bioreactor. 4) That the control of alkali or alkaline earth influences nitrification reaction through bicarbonate/carbonate generation as and product biodegradation of associated phenol load leading to carnonic acid. 9 WE CLAIM : 1. An improved biochemical process for conversion of nitrogenous compound present in the waste water from coke oven so as to produce nitrate nitrogen comprising: treating the waste water so as to remove sludge; subjecting the waste water to biodegradation reaction in bioreactors in the presence of bacteria to effect a nitrification reaction, controlling the flow of the waste water in order to maximize the nitrification reaction and controlling the rate of air supply into the bioreactors ; and providing a pH of between 7-9 to effect optimum nitrification of the nitrogenous compounds present in waste water. 2. An improved biochemical process for conversion of nitrogenous compounds present in coke oven waste water as claimed in claim 1, wherein nitrogenous compounds present in coke oven waste water usually consisting of the following components Compounds mg/litre Ammoniacal nitrogen - 400 - 600 Cyanide - 20-50 Thiocyanate - 150-250 3. An improved biochemical process for conversion of nitrogenous compounds present in coke oven waste water as claimed in claims 1 or 2, wherein the bacteria used in the biodegredation reaction is chosen from existing BOD plants. 10 4. An improved biochemical process for conversion of nitrogenous compounds present in coke oven waste water as claimed in claims 1 or 2, wherein the pH of the mass is controlled by the addition of alkali and alkaline earth compound selected from sodium carbonate, sodium hydroxide and calcium hydroxide. 5. An improved biochemical process for conversion of nitrogenous compounds present in coke oven waste water as claimed in anyone of the preceding claims, wherein the waste water is prior to the step of biodegradation is subjected to cooling to substantially room temperature. 6. An improved biochemical process as claimed in claim 1, wherein the air supply through aeration assembly in the BOD tanks is maintained at a rate of 10-15 litre/hr. 7. An improved biochemical process as claimed in claim 1, wherein the conversion of other forms of N2 in coke oven waste water into nitrate form is between 80 and 90%. 8. An installation for carrying out the process according to any one of claims 1 to 7 comprising : a feed tank in which the waste water from the coke oven is stored and connected to plurality of biodegradation tanks said biodegradation tank connected through clarifiers ; said clarifiers adapted to remove slurge; cooling means for cooling the waste water to substantially room temperature ; a plurality of bioreactor tanks (BOD tank) connected in. series for sequential bioreactor reaction with variation in amount of bacteria and pH variation, said bioreactor tanks having aeration assembly fixed inside; means for feeding the waste water to the biodegradable tanks at a predetermined level". 11 9. An installation as claimed in anyone of the preceding claims, wherein said aeration assembly have ceramic diffuser or mechanical rotating agitator fitted inside the BOD tanks for air supply. 10. An installation as claimed in anyone of the preceding claims, wherein said bioreactors are fitted with mechanical stirrers. 11. Improved biochemical process and installation for conversion of nitrogenous compounds present in coke oven waste water into nitrate substantially as herein described and ascertained with reference to accompanying drawing. Dated this 28th day of March 2000. S. MAJUMDAR of S. MAJUMDAR & CO. Applicants' Agent. 12 A biochemical process for conversion of nitrogenous compound present in the waste water from coke oven consisting of ammoniacal nitrogen, cyanide and thiocyanate. The waste water is treated to remove sludge. It is then subjected to biodegradation reaction in bioreactors in the presence of bacteria to effect a nitrification reaction. The flow of the waste water is controlled in order to maximize the nitrification reaction and the rate of air supply into the bioreactors is also controlled. The treatment is carried out under a pH of between 7-9 to effect optimum nitrification of the nitrogenous compounds present in waste water. The process is affected in a device in which the waste water from the coke oven is stored in a few tank. The waste water is cooled at room temperature and fed to a plurality of biodegradation tanks connected in series through clarifiers, said biodegradation tankers having aeration assembly fixed inside. Means are provided for feeding the waste water to the biodegradable tankers at a predetermined level.

Documents:

00181-cal-2000-abstract.pdf

00181-cal-2000-claims.pdf

00181-cal-2000-correspondence.pdf

00181-cal-2000-description(complete).pdf

00181-cal-2000-drawings.pdf

00181-cal-2000-form-1.pdf

00181-cal-2000-form-18.pdf

00181-cal-2000-form-2.pdf

00181-cal-2000-form-3.pdf

00181-cal-2000-pa.pdf

181-cal-2000-granted-abstract.pdf

181-cal-2000-granted-claims.pdf

181-cal-2000-granted-correspondence.pdf

181-cal-2000-granted-description (complete).pdf

181-cal-2000-granted-drawings.pdf

181-cal-2000-granted-examination report.pdf

181-cal-2000-granted-form 1.pdf

181-cal-2000-granted-form 18.pdf

181-cal-2000-granted-form 2.pdf

181-cal-2000-granted-form 3.pdf

181-cal-2000-granted-letter patent.pdf

181-cal-2000-granted-pa.pdf

181-cal-2000-granted-reply to examination report.pdf

181-cal-2000-granted-specification.pdf