Research On Pretreatment Technology Of Dairy Farm Wastewater

The innovation of science and technology as well as people's increasing demands for dairy products have undoubtedly promoted the vigorous development of dairy farming in China.The wastewater produced by dairy farms has the characteristics of high COD,high SS and high ammonia nitrogen.However,the problem of untreated waste water discharged from most intensive dairy farm,which has seriously threatened the surrounding ecological environment.In view of this situation,Coagulation sedimentation-Alkaline H2O2 oxidation and EGSB process,which were used to investigate the pretreatment effect of physicochemical and biochemical treatment technologies on dairy farm wastewater.Besides,in order to provide technical reference for the construction of dairy farm wastewater treatment facilities,the optimal operating parameters of each process were investigated.The conclusions of this paper are as follows:(1)The pretreatment effect of polyaluminum chloride(PAC),aluminum sulfate(Al2(SO4)3),ferric chloride(FeCl3)and ferrous sulfate(FeSO4)on dairy farm wastewater was compared.The best coagulat was PAC.When the influent concentrations of COD,SS and ammonia nitrogen were 9216mg/L,5140mg/L and 530mg/L,the PAC dosage was 2.5g/L,pH was 7?8,slow stirring time was 16minutes,precipitation time was 25minutes,finally,the removal rate of COD,SS and ammonia nitrogen was 49.1%,71.4%and 21.1%.(2)The test results of Alkaline H2O2 oxidation pretreatment of dairy farm wastewater showed that the alkaline H2O2 oxidation can effectively remove 40%?60%of COD at pH 7?12.When the reaction temperature was 50?,the initial pH was 9,the dosage of H2O2 was 2.72g/L,and the reaction time was 20minutes,at this time,the removal rate of COD was 66.3%.(3)The pretreatment test results of the EGSB process on dairy farm wastewater showed that with the increase of start-up time,the COD removal rate of EGSB reactor is continuously increased,reaching 70%-75%after 3 months of startup.It was considered that the EGSB reactor started successfully and entered the stable operation stage.After 35 days of stable operation,the average removal rate of COD was 80%.(4)The optimum process conditions for the treatment of dairy farm wastewater by EGSB reactor were studied.When the temperature was 35?,influent concentration of COD was 5000mg/L,hydraulic retention time was 16 hours and rising flow rate was 2.2m/h,the removal rate of COD was 85.3%as well as the effluent concentration was 735mg/L.(5)The comprehensive test results showed that the treatment process for treating dairy farm wastewater was Two-stage solid-liquid separation-Coagulation sedimentation-EGSB-Two stage A/O-Alkaline H2O2 oxidation.The ammonia nitrogen in the wastewater could be effectively removed by the two-stage A/O.And finally the alkaline H2O2 oxidation process was used to ensure the discharge of the wastewater.