Crucial Technology Development And Engineerng Design Of An Upgrading And Reconstruction Project For Swine Wastewater Tratement In The North Of China

In response to energy conservation and emission reduction of national strategy,a pig farm located in Heilongjiang Province converts piggery dung cleaning mode into manure-free to reduce the manure emission,water consumption,and required to meet higher discharge standards after the treatment of the wastewater.However,according to the dramatically change in quality and quantity of wastewater,the original treatment process,“Hydrolysis acidification-Biological contach oxidation”cannot fulfill the local standards,and an upgrading is urgent.Normally,SBR,CASS,A/O and Multi-stage A/O are introduced to treat the wastewater,but they cannot remove nitrogen efficiently and cost-effectively because the manure-free piggery wastewater is a kind of high NH₄⁺-N and low C/N ratio wastewater,Thus,for efficiently treating the manure-free piggery wastewater,the bioflim anaerobic/oxic process was employed firstly in the present study as lab-scale,in which the strategy of start-up and the key parameters were confirmed.Secondly,the design of an upgrading and reconstruction project was completed,and the technology and economy of the process were also analyzed.The lab-scale test showed that the biofilm anaerobic/oxic process was feasible to treat manure-free piggery wastewater.The system was successfully started and reached a stable phase at 25?,hydraulic rentention time of 36 h,and the reflux ratio of 200%.During the stable phase,the average influent concentrations of COD,NH₄⁺-N and TN were 1347,524.7 and 636.1 mg/L,respectively,and the average removal rates were as high as 95.1%,92.7%and 88.9%,respectively,as well as the average effluent concentrations of only about 66,38.3 and 70.6 mg/L,respectively.The results indicated that the biofilm anaerobic/oxic process could treat the mannure-free piggery wastewater efficiently,and the effluent can meet the discharge standards required by local governments and enterprises.Analysis of the carbon and nitrogen balance indicated that the nitrogen removal in the anaerobic unit was based on denitrification via NO₂^--N.The main denitrification pathway of aerobic unit was shortcut nitrification and denitrification,and autotrophic denitrification contributed to at least 30.8%.Based on the result of lab-scale test,an integrated technique of solid-liquid separator,coagulation-air flotation,hydrolysis acidification,biofilm anaerobic/oxic process and disinfection with scale of 350 m³/d was selected and designed for treating mannure-free piggery wastewater in large-scale.After the technical and economic analysis?according to the design standards specifications?,the total investment of the upgrading and reconstruction project is 1.39 million yuan,with the operation cost and the total cost of 3.35 and 3.71 yuan/m³,respectively.After the implementation of this project,the COD,BOD₅,NH₄⁺-N,TP,and SS can be removed 306.6,98.4,60.0,2.8,and 200.6 tons per year,respectively.The implementation of the project can produce considerable comprehensive benefits.