Title of Invention

"A PROCESS FOR ANAEROBIC BIODEGRADATION OF HUMAN WASTE AT LOW TEMPERATURE"

Abstract

This invention relates to a process for anaerobic biodegradation of human waste at low temperature in the hilly areas comprising of the steps of preparing pits for biodigester, one pit of diameter of 2.1 to 2.3 m and 2.2 to 2.4 m depth, and second pit of diameter of 1.6 to 2.0 m and depth of 1.8 to 2.5 m for soaking; fixing the biodigester in the pit prepared in step (a) by layering cow dung and cellulose waste mixture as herein described, the said layer of cow dung and cellulose waste mixture has a thickness of 60 cm at the bottom and 25 to 30 cm on dome shaped top; preparing microbial consortium by taking cow dung slurry comprising of hydrolytic, acetogenic, acedogenic and methanogenic anaerobic bacterial consortium, having pH of 7.0 and working at 20°C in a floating dome biodigester, feeding the biodigester with human waste at the rate of 25 days hydraulic retention time (HRT) in continuous mode and then reducing the temperature at a rate of 2°C per 60 days till it is lowered to about 4°C; biodigesting by taking microbial consortium prepared in step (c) in a working volume of 40-60% in the biodigester fixed in step (b) and allowing it to stabilize for 2-3 days.

Full Text

FIELD OF INVENTION This invention relates to an improved process for eco-friendly and safe disposal of human waste by anaerobic biodegradation at low temperature particularly in hilly areas. PRIOR ART There are different types of organic wastes generated by industrial processes like leather, soap, milk, distilleries etc. or produced as excreta of animals and human. These wastes pollute the environment, if not treated properly before discharge. Among these, human waste is of the most serious concern. Being rich in protein, it is subjected to putrefaction by native or surrounding bacteria resulting in foul smell. It increases the Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) level of rivers, ponds, lakes and water streams resulting in depletion of dissolved oxygen and disturbing the aquatic ecosystem. Moreover, human waste is a rich source of various pathogens and thus contaminates drinking water and food sources. Consumption of these may result in various diseases like diarrhea, jaundice, typhoid, cholera and amoebiasis. Traditional processes used to treat human waste can be divided into four categories: physical, chemical, biological and thermal. Of these, biological treatment processes (biodegradation) have been considered as the most attractive alternative primarily due to the conversion of pollutant to environmentally safe products like carbon dioxide, methane and water. The process operates continuously with minimum material and manual input and inactivates most of the pathogens. Biodegradation process is commonly referred as bioremediation, in the art, and is performed as land or hquid treatment. Land treatment is performed mostly through composting of solid waste. Although the method described in the art, is least expensive, it is difficult to perform due to obnoxious nature of the substrate and require adequate amount of land which may not be available in hilly terrain. Another process described in the art is by liquid treatment which is carried out by employing either aerobic or anaerobic bacteria. One of the disadvantage of aerobic processes used generally .require water of low BOD value and require agitation and aeration for efficient biodegradation. Another disadvantage of the process is the need of high oxygen transfer which generates higher cell mass termed as sludge and thus needs to be removed by secondary treatment. A method described for anaerobic treatment of liquid waste is an old and well established technology, and was practiced in the middle east, many centuries before Christ, for waste water having high BOD commonly ranging between 2000 - 100000 mg / ml. The anaerobic fermentation as described in the art is carried out in four steps by four different types of hydrolytic, acidogenic, acetogenic and methanogenic bacteria. The final product of the process is methane which is a clean fuel. The process inactivates most of the pathogens and very little sludge is generated as compared to aerobic treatment. The main disadvantage of the process described in the above art is that the process works only at mesophihc temperatures and is ineffective at higher reaches of Himalayas where the ambient temperature falls to -30°C and lower. Another method described in the art for disposal of human waste at higher reaches of Himalayas where the ambient temperature falls to -30°C and lower is that the human waste is either buried under the soil (Deep Trench Latrine) or accumulated throughout the winter session in Laddhaki type toilet. The disadvantage of these methods is that the waste is not subjected to full decomposition and there is a risk of polluting water bodies. Another disadvantage is that the waste accumulated in the laddhaki toilet is transferred to the field causing foul smell in adjoining area. Yet another disadvantage is that there is a risk of pathogens contaminating the environment and food sources. Another process known in the art for treatment of human waste is the biodegradation process by which biogas is produced. The limitation of the process is that it works very well at 30°C and above but becomes ineffective at subzero temperature Therefore there is a need for a process which can easily and continuously degrade the human waste at subzero temperature. The process should not require additional energy or should require minimum energy through sources easily available in the locality. QBJECTS OF PRESENT INVENTION The main object of the present invention is to provide an improved process for anaerobic biodegradation of human waste at low temperature in hilly areas. Another object of the present invention is to provide an anaerobic biodegradation process which is easy, cost effective and eco-friendly. Yet another object of the present invention is to provide an anaerobic biodegradation process which is continuous and sustainable at various environments. Further object of the present invention is to provide an anaerobic biodegradation process which does not require external source of energy. Yet further object of the present invention is to provide an anaerobic biodegradation process which can degrade up to 90% of the human waste. Still further object of the present invention is to provide an anaerobic biodegradation process which can convert human waste into an odorless gas. The other object of the present invention is to provide an anaerobic biodegradation process wherein the out coming effluent has less than 10% stabilized organic /inorganic matter. Another object of the present invention is to provide an anaerobic biodegradation process which inactivates the pathogenic bacteria during fermentation process.DESCRIPTION OF INVENTION According to this invention there is provided a process for anaerobic biodegradation of human waste at low temperature in the hilly areas comprising of the steps of: a) preparing pits for biodigester, one pit of diameter of 2.1 to 2.3 m and 2.2 to 2.4 m depth; and second pit of diameter of 1.6 to 2.0 m and depth of 1.8 to 2.5 m for soaking; b) fixing the biodigester in the pit prepared in step (a) by layering cow dung and cellulose waste mixture as herein described, the said layer of cow dung and cellulose waste mixture has a thickness of 60 cm at the bottom and 25 to 30 cm on dome shaped top; c) preparing microbial consortium by taking cow dung slurry comprising of hydrolytic, acetogenic, acedogenic and methanogenic anaerobic bacterial consortium, having pH of 7.0 and working at 20°C in a floating dome biodigester, feeding the biodigester with human waste at the rate of 25 days hydraulic retention time (HRT) in continuous mode and then reducing the temperature at a rate of 2°C per 60 days till it is lowered to about 4°C; d) biodigesting by taking microbial consortium prepared in step (c) in a working volume of 40-60% in the biodigester fixed in step (b) and allowing it to stabilize for 2-3 days. The anaerobic microbial consortium has the ability to function at the lowest temperature of 5°C. However, it works efficiently at 10°C to 35°C and can tolerate up to 2 cycles of freezing and thawing, if encountered during the installation of biodigester. Fluctuation of the temperature in the range of 5 to 35°C does not affect the consortium and its fermentation efficiency. The process inactivates the bacterial pathogens and 90% of waste is converted into biogas which is 65-72% methane. It is an eco-friendly and cost-effective process which is sustainable continuously in various environments without the requirement of any external source of energy. DESCRIPTION OF THE PROCESS; According to the present invention the process for anaerobic biodegradation of human waste at low temperature in the hilly areas comprises of the steps of: a) Preparation of Pits: A pit of 2.1 to 2.3 M diameter and 2.2 to 2.4 M depth is dug. Bottom of the pit is layered by cow dung mixture comprising of cow dung and cellulose wastes like wheat straw, leaves etc. in the ratio of 1:1. The cow dung mixture is filled up to about 60 cm at the bottom. Another pit (soak pit) of size 1.6 - 2.0m diameter and 1.8 - 2.5m depth is made for collection of effluent, 0.7 - 1.0m away from the biodigester pit. It is covered with galvanized iron sheet or concrete slabs. b) Fixing the Biodigester: The biodigester a cylindrical structure made up of 3 - 6 mm preferably 4-5 mm thick mild steel, comprising of a dome shaped top, inlet pipe, outlet pipe, gas pipe, working chamber and a partition, is placed in the centre of the pit made in step a). The surrounding gap of about 60 cm around the biodigester is filled with the cow dung mixture. Top of the biodigester is covered with cow dung mixture (25 - 30 cm) followed by soil to make it upto the ground level. The inlet pipe of the biodigester is connected to 4 - 6 number of toilets through a chamber of size 60 cm x 50 cm x 50 cm (W x L X D). The distance of chamber from the biodigester should be the closest possible and the distance of toilet commode from the chamber should not be more than 1 mefre. The connecting pipes are made of cement / PVC, and are buried 20 cm to 40 cm preferably 25 - 30 cm below the ground level. These pipes are covered up to a thickness of about 15 cm all around by cow dung mixture. The outlet pipe of the biodigester is connected to the soak pit prepared in step a). c) Preparation of Microbial Consortium: In a floating dome biodigester 40-60% preferably 50-55% of working volume, cow dung slurry having pH value of 7.0, comprising of hydrolytic, acetogenic, acedogenic and methanogenic anaerobic bacterial consortium, working at about 200C, is taken. The biodigester is fed with human waste at the rate of 25 days Hydrauhc Retention Time (HRT) in continuous mode. The temperature of the biodigester working at about 20°C is reduced at a rate of 2°C per 60 days till the temperature is lowered to about 4°C. d) Biodigestion Process: Microbial consortium or the inoculum prepared in step c) is filled in to the biodigester of step b) through a chamber connected to the inlet pipe of the biodigester. Inoculum occupies 40 - 60% preferably 50 - 55 % of the working volume. It is allowed to stabilize for 2 - 3 days till biogas production starts. The amount of feed material to the biodigester is calculated in terms of Hydraulic Retention Time (HRT) which indicates that in how many days the volume of biodigester slurry will be replaced. In other words' HRT is equivalent to working volume of the biodigester divided by feed material per day. The biodigester of the present invention operates at HRT of 25 - 35 days preferably 25 - 30 days and is used by 50 - 60 persons. Each person uses one to two litre of water for washing purposes. Washing water and human waste serves as feed material for biodigeter. Effluent in the soak pit contains less than 10% of the volatile sohds as compared to feed material and bacterial pathogens are inactivated. Biogas contains 65 - 72% methane content. This invention will now be illustrated with a working example, which is intended to be typical example to explain the technique of the present invention and is not intended to be taken restrictively to imply any limitation to the scope of the present invention. WORKING EXAMPLE A pit of 2.0 M diameter and 2.2 M depth was dug. Bottom of the pit was layered by cow dung mixture comprising of cow dung and cellulose wastes like wheat straw, leaves etc. in the ratio of 1:1. The cow dimg mixture was filled up to 60 cm at the bottom. The biodigester was placed in the centre of the pit. The surrounding gap of about 60 cm around the biodigester was filled with the cow dung mixture. On the top of the biodigester 20 cm soil was filled in the pit. Another pit (soak pit) of size 1.6m diameter and 1.8m depth was made for collection of effluent, 0.7m away fi-om the biodigester pit. It was covered with galvanized iron sheet. The inlet pipe of the biodigester was directly connected to the toilets commode and the outlet pipe was connected to the soak pit. The biodigester provided complete anaerobic condition (devoid of oxygen). The microbial consortium was filled in to the biodigester through inlet pipe to occupy 50% of the working volume. It was allowed to stabilise for 3 days till biogas production started. The inlet of the biodigester was connected to 6 toilets (for 50 person waste). The hydraulic retention time was kept at the rate of 25 days. The biogas was collected through a gas pipe fitted with nozzle projecting from the top of the biodigester and tested for inflammability. It is understood that the process of the present invention is susceptible to modifications, changes, adaptations by those skilled in the art. Such modifications, changes adaptations are intended to be within the scope of the present invention which is further set forth under the following claims: I CLAIM; 1. A process for anaerobic biodegradation of human waste at low temperature in the hilly areas comprising of the steps of: a) preparing pits for biodigester, one pit of diameter of 2.1 to 2.3 m and 2.2 to 2.4 m depth; and second pit of diameter of 1.6 to 2.0 m and depth of 1.8 to 2.5 m for soaking; b) fixing the biodigester in the pit prepared in step (a) by layering cow dung and cellulose waste mixture as herein described, the said layer of cow dung and cellulose waste mixture has a thickness of 60 cm at the bottom and 25 to 30 cm on dome shaped top; c) preparing microbial consortium by taking cow dung slurry comprising of hydrolytic, acetogenic, acedogenic and methanogenic anaerobic bacterial consortium, having pH of 7.0 and working at 20°C in a floating dome biodigester, feeding the biodigester with human waste at the rate of 25 days hydraulic retention time (HRT) in continuous mode and then reducing the temperature at a rate of 2°C per 60 days till it is lowered to about 4°C; d) biodigesting by taking microbial consortium prepared in step (c) in a working volume of 40-60% in the biodigester fixed in step (b) and allowing it to stabilize for 2-3 days. 2. A process as claimed in claim 1 wherein the pits are at a distance of 0.7 to 1.0 m from each other. 3. A process as claimed in claim 1 wherein the inlet pipe of the biodigester is connected to 4-6 toilets. 4. A process as claimed in claim 1 wherein the outlet pipe of the biodigester is connected to soak pit. 5. A process as claimed in claim 1 wherein the biodigester operates at hydraulic retention time of 25-35 days preferably 25-30 days. 6. A process as claimed in claim 1 wherein the water used for washing purposes is 1-2 litres. 7. A process for anaerobic biodegradation of human waste as substantially described and exemplified herein.

Documents:

262-DEL-2004-Abstract (25-01-2010).pdf

262-del-2004-abstract.pdf

262-DEL-2004-Claims (25-01-2010).pdf

262-del-2004-claims.pdf

262-DEL-2004-Correspondence-Others (25-01-2010).pdf

262-del-2004-correspondence-others.pdf

262-del-2004-correspondence-po.pdf

262-DEL-2004-Description (Complete) (25-01-2010).pdf

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

262-del-2004-form-1.pdf

262-del-2004-form-2.pdf

262-DEL-2004-Form-3 (25-01-2010).pdf

262-DEL-2004-GPA (25-01-2010).pdf