High Temperature Coal Tar Hydrogenation Wastewater Improved Biological Enrichment-multi-stage AO Experimental Study

At the beginning of the 21 st century,China began to develop high-temperature coal tar hydrogenation technology to alleviate the pressure on China's energy demand.However,the discharge of high temperature coal tar hydrogenation wastewater can not meet the national standards,which restricted the development of this technology.The treatment of high temperature coal tar hydrogenation wastewater needs to be solved urgently.This paper takes the simulation of high temperature coal tar hydrogenation wastewater as the research object.,and the modified biological enrichment-multi-stage AO system combined treatment is carried out,focusing on the treatment performance of COD,volatile phenol and ammonia nitrogen,exploring the main influencing factors and the best processing conditions.In this study,from the perspective of cost-effectiveness,bio-filler is used instead of powdered activated carbon to improve the biological enrichment process,so as to increase the sludge concentration in the bio-enrichment system,and to create high sludge concentration,long sludge age and low dissolved oxygen.The treatment environment creates conditions for microbes and simultaneous nitrification and denitrification with long generations.In view of the characteristics of high temperature coal tar hydrogenation wastewater,multi-point water injection is adopted to improve the nitrogen removal performance of multi-stage AO process.Firstly,the system is started with the actual domestic sewage.When the activated sludge reaches a certain amount in the system,the wastewater is added for domestication,which shortens the sludge cultivation time.The influent concentrations of COD,volatile phenol and ammonia nitrogen in the acclimation period are 111.6~772mg/L,48.9~121mg/L,57.37~127.89mg/L,respectively.The effluent concentration of COD,volatile phenol and ammonia nitrogen in the modified biological enrichment system are 91.63mg/L,4.65 mg/L,9.68 mg/L.The removal rate reaches 80%,95.02%,86.88%.The effluent concentrations of COD,volatile phenol and ammonia nitrogen in multi-stage AO system are 126.83 mg/L,5.23 mg/L and 3.89 mg/L,and the removal rates are 80%,94.34% and 94.89%,respectively.When domestication is completed and stable operation,the high-throughput sequencing is used to compare and analyze the population structure of the modified bioconcentration system and multi-level AO system.Studies show that Proteobacteria,Bacteroidetes and Firmicutes are the most dominant bacteria in the two systems.In addition,Verrucomicrobia has an advantage in modified biological enrichment systems.The multi-stage AO system achieves nitrification and denitrification and denitrification under the combined action of bacteria such as Haliangium,Nannocystis,Dokdonella,Brachymonas,Paludibacter and Trichococcus.In the continuous operation phase,this study investigats the effects of different hydraulic retention time(HRT),mixture reflux ratio and sludge reflux ratio on the treatment efficiency of the modified biological enrichment system.The research shows that the influent concentrations of COD,volatile phenol and ammonia nitrogen are 1100~1300mg/L,211~300mg/L,150~210mg/L.Under the test conditions of HRT=36h,mixture reflux ratio of 200% and sludge reflux ratio of 75%,the modified biological enrichment system has the best treatment performance.The average effluent concentrations of COD,volatile phenol and ammonia nitrogen are 345.66mg/L,10.46mg/L,87.97mg/L,and the average removal rates are 71.15%,96.1%,56.03%,respectively.The study finds that the modified biological enrichment system greatly reduces the concentration of COD and volatile phenol,improves the biochemical properties of wastewater,and creats favorable processing conditions for the subsequent denitrification process.The effects of different HRT,water inflow ratio and sludge reflux ratio on the nitrogen removal performance of multi-stage AO system are further explored.Under the conditions of HRT=36h,the water inflow ratio is 1.3:1:0.7,and the sludge reflux ratio is 75%,the multi-stage AO system has the best nitrogen removal effect,the average effluent concentration is 14.21mg/L,and the average removal rate reaches 86.73%.