| With the rapid development of intensive pig industry,the amount of pig manure excretion and total amount of TN and COD pollutants increased rapidly.Anaerobic digestion is currently the mainstream technology for pig manure treatment,but the content of NH4+-N in anaerobic digestion solution is far.Higher than the "Emission Standards for Pollutants in Livestock and Poultry Industry"(GB 18596-2001),if it is not effectively disposed,it will generate huge environmental pressure.The pig manure anaerobic digestion liquid has the characteristics of low COD/NH4+-N,so the traditional nitrification and denitrification treatment of anaerobic digestion liquid usually requires an external carbon source,and the cost is high.In contrast,short-range nitrification and denitrification reduces the demand for carbon sources by 40%,the demand for oxygen by 25%,and has the advantages of faster reaction rate and smaller reaction volume,and is more suitable for treating low COD/NH4+-N.Waste water.Aiming at short-range nitrification and denitrification treatment of pig manure anaerobic digestion solution,rational allocation of carbon source,exploring the effect of nitrogen removal under different loads and clarifying the mechanism of microbial action is the key content of the research.The content of this experiment is divided into three parts.The first part uses SBR reactor to directly treat pig manure anaerobic digestion liquid,and discussed the feasibility of short-term nitrification and denitrification to directly treat anaerobic digestion liquid.The second part focuses on different loads.The effect of pig manure raw water as carbon source(ZF-SBR)and sodium acetate as carbon source(YS-SBR)on nitrogen removal efficiency;the third part analyzes the diversity of microorganisms in the reactor and the structure analysis.The main work and conclusions are as follows:(1)Directly treating the diluted pig manure anaerobic digestion solution with SBR.Under the influent ammonia nitrogen concentration of 50 mg/L and 200 mg/L,the ammonia nitrogen conversion rate is greater than 84%,but the nitrate nitrogen in the effluent The concentration of nitrite nitrogen is too high,the removal rate of TN is only 10-20%,and the alkalinity in the system is insufficient,and the p H is lowered to below 6.Even if it is difficult to increase the TN removal rate by optimizing the reactor operating conditions,it is not feasible to directly treat the pig manure anaerobic digestion solution by short-cut nitrification and denitrification.(2)Using the pig manure raw water and sodium acetate as the organic carbon source,the operation of the two reactors under different load conditions was investigated.The results show that the denitrification effect of the two reactors is basically the same,in which ZF-SBR obtains the maximum TN removal rate(70%)at the influent concentration of 500 mg N/L;the YS-SBR has an influent concentration of 400 mg N/L.The maximum TN removal rate(78.4%)was obtained.At higher influent concentrations(?500 mg N/L),the denitrification effect of pig manure raw water as carbon source is significantly better than that of acetic acid carbon source.The use of pig manure raw water as a carbon source to treat high-concentration pig manure anaerobic digestion liquid can meet the demand of short-cut nitrification and denitrification without the need of an external carbon source.(3)By increasing the influent ammonia nitrogen load,the total nitrogen removal load(NRR)reached a maximum of 190.6 mg N L-1 d-1 when the pig manure raw water was used as the carbon source reactor in the fourth stage influent ammonia nitrogen concentration was 600 mg L-1 d-1,at this time NRR=0.72 NLR,the average TN removal rate was 67.9%,and the highest TN removal rate was 74.8%.Therefore,when the pig manure raw water is used as the carbon source,the reactor operates at the best condition: the pig manure anaerobic digestion liquid is diluted to a concentration of ammonia nitrogen of about 600 mg/L,the reaction process control temperature is 25?,and the dissolved oxygen is 2 mg/L in the aeration stage,sludge retention time is 13 d.(4)The results of microbial high-throughput analysis showed that the biocommunity of the reactor with the raw material of pig manure as the organic carbon source was higher and the uniformity was better than that of the reactor with sodium acetate as the external carbon source.When the pig manure raw water was used as the organic carbon source,the relative abundance of the denitrifying bacteria in the reactor(9.80%)was greater than that of the reactor with sodium acetate as the carbon source(6.72%).The dominant denitrifying bacteria were Comamonas(3.33%),unclassified_f__Comamonadaceae(1.69%),Ottowia(1.63%),paracoccus(1.51%)and Thauera(1.11%)when pig manure raw water was used as the carbon source. |
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