Study On The Treatment Of Dairy Farm Biogas Slurry By Combined Process

At present,with our level of consumption is increasing, the living standard is improving, people’s demand for dairy products is expanding and the farming dairy plant is increasingly mature.The dairy plant wastewater by anaerobic fermentation, producing a large amount of biogas slurry.The biogas slurry has the following characteristics:high content of organic matter and ammonia nitrogen, carbon and nitrogen ratio is imbalance,poor biodegradability.Therefore, efficient control and management of biogas slurry pollution from dairy farm is imperative.This paper proposed the use of MAP-Coagulation and MAP-SBR to treat the dairy farm biogas slurry, and compared the treatment effect and economic benefit with the two combined process by analysising and studying the water quality of the Shanghai Chongming County Guangming Dairy Farm biogas slurry.MAP, namely the struvite method, also known as magnesium ammonium phosphate precipitation method, is the method of removal of nitrogen and phosphorus in dairy farm biogas by the utilization of magnesium ion, phosphate ions and ammonium ions to produce magnesium ammonium phosphate precipitation.Experiments show that the optimum experimental conditions of the MAP method as the dairy farm biogas slurry pretreatment were:about 26 degrees with the temperature, the reaction time is 10min, the stirring speed is 100r/min, pH=9.0, n (Mg2+):n(PO43"):n (NH4+) is 1.2:1:1. Under this condition, ammonia nitrogen, total phosphorus and CODcr removal rate reached 94.27%,97.82% and 68.84% respectively.Using the coagulation method and SBR method treat the effluent of dairy farm biogas after pre treatment. The experiment through the study on the coagulation method, the optimum experimental conditions of the reaction is pH=8-9,coagulant dosage of FeCl3 is 7.5mL/L, the reaction time is 5min, coagulant aids dosage of PAM is 1.0mL/L, CODcr, ammonia nitrogen and phosphorus removal rate is 90.08%, 73.36% and 99.82%respectively., and the value of the ammonia nitrogen in the wastewater is 9.82mg/L, the CODcr value is 146.6mg/L and the total value is 0.07mg/L.All these index can meet the requirements of the "discharge standard of pollutants" (GB18596-2001).Through the SBR method treat the effluent of dairy farm biogas after pre treatment. Using this method compared the removal efficiencies of CODcr, ammonia nitrogen and phosphorus with conventional activated sludge and aerobic granular sludge. Experiments show that, when the SBR water concentration of CODcr, ammonia nitrogen and total phosphorus is about 896mg/L, about 21mg/L and about 24mg/L,the CODcr, ammonia nitrogen and total phosphorus in SBR1 effluent is 422.26mg/L,5.56mg/L and 6.58mg/L; the CODcr, ammonia nitrogen and total phosphorus in SBR2 effluent is 267.5mg/L,3.56mg/L and 5.19mg/L. It can conclude that the treatment effect of aerobic granular sludge is better than the conventional activated sludge, the effluen concentration in SBR2 can reach the requirements of the "discharge standard of pollutants"(GB18596-2001).By comparing the treatment of the biogas slurryof Guangming dairy farm, Chongming County, Shanghaiwith the MAP-Coagulation method and MAP-SBR method. It can conclude that the two combined process all can meet the standard and do resource recovery of biogas slurry. But contrast the operation effect and economic benefit with the two process, choosing the MAP+SBR method is more suitable.