Study On Pretreatment Of High Concentration Piggery Wastewater By MBBR Process Inoculated With Bacteria

The extremely high concentrations of ammonia and organics of piggery wastewater causes severely adverse environmental issue.Thus,piggery wastewater requires adequate treatment before it is directly discharged.Anaerobic treatment,as a pretreatment technology for high concentration piggery wastewater,its efficiency is easily affected by tank volume and temperature.And after anaerobic treatment,there is a low C/N ratio of effluent,which requires a complicated process flow for further processing.Therefore,it is urgent to find a new pretreatment process to treat high concentration piggery wastewater.A low-cost and high-efficiency MBBR pre-process for the piggery wastewater has been proposed in this research.In the novel MBBR,HN-AD bacteria with high tolerance and removal capacity were used as inoculum（HMBBR）to replace the traditional activated sludge,which solved the problems of long start-up time and poor TN removal capacity in the traditional biological process under high ammonia conditions.The effect of ammonia nitrogen concentration on pollutant removal performance and the microbial community in MBBRs（K1 and PVA as carrier,namely K-HMBBR and P-HMBBR）has been comparied.Confirmed that PVA is more suitable as a carrier for the new MBBR.At the same time,the parameters were optimized by adjusting the influent C/N ratio and hydraulic retention time（HRT）.Based on this,in order to further improve the performance of the new MBBR for pretreating high-concentration piggery wastewater,the Acinetobacter sp.TAC-1 is used to bioenhance the performance of the process.Pollutants of real piggery wastewater can be largely removed by this process.Finally,Illumina Mi Seq sequencing technology and SEM characterization were used to observe the changes of microbial community and obtain the information of key bacteria.functional gene prediction was used to reveal functional genes and nitrogen cycle pathway,which provide a theoretical basis for the engineering application of the new MBBR process.The MBBR inoculated with HN-AD bacteria provides a feasible method for the industrial application of high NH₄⁺concentration of piggery wastewater treatment.The main conclusions are as follows:（1）Compared with the MBBR started up by traditional activated sludge,MBBR stared up by HN-AD bacteria can effectively shorten the start-up time from 39 d to 15 d,and significantly increase NH₄⁺-N removal efficiency from 34.6%to 90.7%.HN-AD bacteria as the inoculum is conducive to start up MBBR process in a short time,at the same time to achieve effective removal of nitrogenous substances.Compared with the K1,PVA is more suitable for the MBBR process started up by the bacteria.MBBR with PVA as carrier can increase the tolerance to ammonia nitrogen to 900 mg/L.The 76.7%of NH₄⁺-N and 73.3%of TN can be removed when the influent NH₄⁺-N is higher than 900 mg/L.The porous structure of PVA can protect the growth of bacteria to a certain extent and reduce the toxicity.The relative abundance of nitrogen removal bacteria（Acinetobacter,Pseudomonas,Paracoccus,Flavobacterium,Arcobacte and Rhocococcus）in P-HMBBR is about 27%,which can ensure high-efficiency nitrogen removal performance under high ammonia nitrogen conditions.（2）The optimal influent C/N ratio and HRT for P-HMBBR process operation are 6～10and 48 h.Under the best operating conditions,better removal performance of COD,NH₄⁺-N and TN can be achieved.Paracoccus and Acinetobacter are key functional bacteria that perform nirogen removal at low C/N ratios.As HRT was 48h,Acinetobacter,Flavobacterium,Paracoccus,Thaurea,Alcaligenes and other nirogen removal bacteria had the highest total relative abundance of 47.42%.This is conducive to the effective removal of pollutants.（3）The optimum inoculation amount of Acinetobacter sp.TAC-1 strain bioaugmentated P-HMBBR is 15%.The bioaugmentated P-HMBBR can achieve 86.16%,95.22%and 85.57%removal efficiency of COD,NH₄⁺-N and TN within 24 hours.P-HMBBR process treats the real water collected from pig farm in Chongqing Banan Longqiao Farm,the removal efficiency of COD,NH₄⁺-N and TN were 84.85%,95.01%and 86.40%,respectively.The NH₄⁺-N concentration of the effluent is below 45 mg/L,which has reached the“Emission Standard of Pollutants for Livestock and Poultry Farming”.P-HMBBR bioaugmentated by Acinetobacter sp.TAC-1 can greatly remove the pollutant content of real piggery wastewater.（4）After P-HMBBR was bioaugmentated by Acinetobacter sp.TAC-1,the relative abundance of nitrogen removal bacteria increased from 9.78%to 22.93%,especially Acinetobacter with function of HN-AD significantly increased from 0.12%to 6.69%,which is conducive to the nitrogenous substances removal.During the process of treating real piggery wastewater,the microbial diversity was increased because the microorganisms in the real wastewatee are fused with the microbial community in the original P-HMBBR.And the advantageous HN-AD bacteria will be changed from Acinetobacter to Rhodococcus to ensure efficient removal of pollutants.PICRUSt2 prediction analysis showed that the total relative abundance of nitrogen removal genes increased from 0.092%to 0.101%after Acinetobacter sp.TAC-1 bioaugmentated P-HMBBR.Bioaugmention is conducive to the increasing of nitrogen removal genes,so that the nitrogen removal performance of P-HMBBR is enhanced.From the perspective of nitrogen metabolism,DNRA and denitrification are the main metabolic pathways of P-HMBBR.