| The livestock wastewater is one of the main sources of pollutants in China,which is characterized by high concentrations of COD,suspended solid,ammonia nitrogen and phosphorus,pathogens.Dairy wastewater is usually treated by Anaerobic digestion is often used for the treatment of livestock wastewater such as dairy wastewater due to methane recovery and high organic loading.In practical engineering,anaerobic digestion performance is easily affected by many parameters such as environmental temperature,causing high concentration of suspended solid,nitrogen,phosphorus and inert and process defects,resulting in the high concentration of suspended matter,nitrogen and phosphorus pollutants,inert and residual degradable organic matter to be remained in the biogas slurry.Anammox has drawn extensive attention because of the low cost and high efficiency in nitrogen removal.In this paper,the performance of a full-scale anaerobic digestion of dairy wastewater in Lu’an Jinhe dairy farm is firstly investigated;Then,the effect of residual organic matter on partial nitrification system is evaluated using synthetic wastewater in laboratory.Finally,based on the above results,we design dairy wastewater process,e.g,pretreatment-partial nitrificationAnammox,whereby the partial nitrification process is started.The main conclusions drawn from this research are presented as follows:(1)Firstly,the performance of a full-scale anaerobic digestion of dairy wastewater is investigated.The effects of anaerobic digestion on the dairy farm were investigated.The effect of solid-liquid separation was inefficient in dairy farms,and the concentration of SS is as high as 10～15 g/L as the in influent of anaerobic digestion.The performance of anaerobic digestion fluctuated greatly.The concentration of COD in the effluent is 1500～3500 mg /L,and its removal rate is 40%～60%.The SS removal rate is 50%～80%.In order to evaluate the performance of anaerobic digestion,the effluent from the anaerobic digester of dairy farm is analyzed using vial experiments.The concentration of COD is 1500～3500 mg /L in the effluent of anaerobic digestion,the COD removal rate is 40%～60%,and the SS removal rate is 50%～80%.In order to evaluate the performance of anaerobic digestion process,the effluent of anaerobic digestion is analyzed by vial experiment.The results shows that the methane accumulation yield of biogas slurry is as high as 255.5 m L/g VSS after anaerobic digestion in the laboratory from 6℃,which is nearly 100% higher than that from15～20℃.Anaerobic digestion is effective for the inactivation of coliform in the wastewater,the content of coliform is reduced by 1.5～2.0 log in the wastewater,which improves the safety of dairy farm wastewater.However,the inactivation effect of Enterococcus was not effective,which is only reduced by 0.5～1.0 log,and follow-up disinfection treatment should be needed.The study shows that the performance of anaerobic digestion process is significantly affected by the environmental temperature,so it is necessary to fully consider the winter insulation measures in practical engineering,and to optimize the solid-liquid separation and sludge drainage system to avoid the accumulation of SS in the reactor of dairy farm.(2)The effect of residual organic matter on the partial nitrification system is investigated.Protein and sodium humate are added after the quickly start-up of two partial nitrification reactors.After protein is added to the partial nitrification system,both aerobic digestion and denitrification are realized in the reactor,and the partial nitrification effect is not affected.The maximum activity of the ammonia oxidizing bacteria was 31.7 mg N/(L· h).Sodium humate would not be degraded and utilized in the partial nitrification system,which would inhibit the activity of ammonia oxidizing bacteria in the initial stage.As the operation in the reactor,the activity of ammonia oxidizing bacteria quickly recovered and increased to 25.7 mg N/(L· h).In the stable stage,the removal rate of ammonia nitrogen is reached 100%,and the accumulation rate of nitrite nitrogen is stabilized at about 90% in both reactors.The results shows that the biogas slurry of anaerobic digesting with degradable and inert organic matter can be realized the application of partial nitrification process.(3)Finally,according to the actual water quality of biogas slurry,physical filtration and chemical flocculation methods are used to pretreat biogas slurry in dairy farms.In dairy farms,rapid sand filtration and low concentration polyaluminum chloride is used to pretreat the biogas slurry to remove SS.The process flow of biogas slurry denitrification is designed,based on which the corresponding denitrification treatment device is designed and built in Jinhe dairy farm.The start-up scheme of the process is designed and the start-up process of biogas slurry partial nitrification is investigated.Low temperature and high concentration of COD and SS leaded to the partial nitrification reactor in the start-up process mainly to remove suspended solids and aerobic digestion of organic matter.During the operation period,the total nitrogen removal rate is about 10% without nitrite accumulation,indicating the existence of weak denitrification and ammonia oxidation activities. |
