Study On Treatment Of Livestock Wastewater Using A Combined Simultaneous Methanoge-Nesis And Denitrification (SMD)-Shortcut Nitrification And Denitrification Process

Livestock wastewater has become one of the three water pollution sources asso-ciated with industrial wastewater and sewage, which is harmful to air, water and soil,but it is also rich in resources and has high recycling values, we can obtaine the effec-tive resources from it by adequate treatment properly.It has the characteristics of "threehighs": high ammonia nitrogen concentration, high organic matter concentration, highsuspended solids concentration. If livestock wastewater is dicharged directly or withoutadequate treatment, it would cause great harm to the environment. Nitrogen pollutionhas become a major problem, therefore it must be disposed appropriately before emis-sions.By comparing the domestic wastewater disposal technology with the overseas, aclear conclusion is obtained that the current processes are concentrated on the COD andNH₄⁺-N removal only, NH₄⁺-N is transformed to NO_x^--N, total nitrogen has not beeneffectively removed. In another words, it will continue to cause potential hazard to wa-ter body. A joint process,in which a Continous Stirred Tank Reactor（CSTR） was used asthe simultaneous methanogenesis and denitrification reactor and a Modified Sequec-ing Batch Reactor （MSBR） as the shortcut nitrification and denitrification reactor,waspromoted.Then the joint process was applied in a pilot-scale wastewater treatmenton-site.slaughtering The research focused on examining the removal effect of variouspollutants through the joint process and analysing of the removal path of pollution sub-stances; Then running performance of CSTR and MSBR was assessed; Finally, theenergy consumption of the entire operation was evaluated.By limiting the amount of aeration to0.13m³/h, the dissolved oxygen of theMSBR aeration tank and SBR tanks was0.7¹.2mg/L at the most, as a result theshortcut nitrification and denitrification was acheived; Then the effulent of MSBR wasdraw back to the CSTR by a certain percentage, mixing with the original water and thesimultaneous methanogenesis and denitrification was realized. After one-year-prac-tice,there has come to several conclusions as follows:（1） Stable and efficient removal ofcontaminants is got under the condation of great changes of the inffulent load. The re-moval efficiencies of COD、NH₄⁺-N、TN reaches97.12%、95.13%、77.14%respectively;and the effluent COD keeps below80mg/L, NH₄⁺-N keeps below15mg/L, TN keepsbelow30mg/L.（2） The main role of CSTR is the removal of COD, the NO_x^--N remov- al via denitrifying, and transformation organic nitrogen into ammonia nitrogen; TheCOD, TN, NH₄⁺-N removal contribution rates of CSTR are68.35%、27.66%、-33.42%.respectively. The main role of MSBR is TN, NH₄⁺-N removal, and further re-moval of COD; The COD, TN, NH₄⁺-N removal contribution rates of MSBR are31.65%、72.34%、133.42%, respectively.（3） The optimum reflux ratio is75%, underwhich, the NO_x^--N removal rate of CSTR is nearly100%and the CH4content of thebiogas is66.70%.along with high methanogenic activity of anaerobic sludge. combinedprocess should run in a low reflux ratio, mainly relying on the TN removal of MSBR.（4）Shortcut nitrification and denitrification shows an obvious seasonal law:in the tropicalsummer, the NAR（Nitrite Accumulation Rate） maintains at more than65%stably; incold winter,the NAR fluctuates around50%volatility.The stability of the NAR and theTN removal rate are positively correlated. Free ammonia （FA） inhibition and low dis-solved oxygen are key factors to achieve shortcut nitrification and denitrification.（5）The BOD₅removal rate of the joint process is above98%, the total phosphorus andoil are eliminate partly.