Efficiency And Biofilm Flora Structure Response Relation In The SMBBR Treatment Of The Coking Wastewater

Coking wastewater is produced in the process of high-temperature carbonation,gas purification and chemical refining in coking plant.It contains high concentration ammonia and stubborn organic pollutants,such as phenol,long-chain alkane,polycyclic aromatic hydrocarbon and N,O,S heterocyclic compounds,etc.it is one of the most difficult wastewater to be treated at present.Therefore,to explore the biotransformation process of the pollutants contained in it is helpful to explore the reaction mechanism,process improvement,dynamic monitoring and optimal control of coking wastewater treatment,and improve the efficiency of wastewater treatment.In this paper,the specific moving bed biofilm reactor(SMBBR)was used to treat the coking wastewater after anaerobic pretreatment.By optimizing the process parameters,the treatment effect was optimized.The interaction between the pollutants degradation in the reactor was evaluated by HS-GC/Ms.Illumina Miseq sequencing platform was used to identified the relationship between dominant microorganisms and pollutant degradation and transformation,and explored the relationship between environmental changes caused by pollutant degradation and the structure of biofilm flora through canonical correspondence analysis(CCA).The film was hung by the method of airtight aeration and sludge discharge.By adjusting the process parameters such as Hydraulic Retention Time(HRT),pH value,Dissolved Oxygen(DO)and temperature,the system membrane was started to complete,and the influence of different influencing factors on the wastewater treatment effect was explored.The response surface method was used to optimize the process operation parameters to find the best operation conditions of the system,so as to optimize the processing efficiency.When DO concentration was 4-6 mg/L,pH value was 7.5-8.5 and HRT was 5-6 days,the removal efficiency of organic matter in coking wastewater was better.The reaction process was optimized and predicted by the response surface model and the best operating conditions were:DO concentration was 5 mg/L,pH was 8,and HRT was 5 days.At this time,the COD removal rate reached 84.51%.Continuously monitor the aerobic treatment effect of bioreactor,explore the interaction between pollutant degradation,detect the components of organic pollutants in the system,and analyze the degradation of organic pollutants.The results show that the system still has good treatment effect when the influent water quality fluctuates greatly.Among them,phenol can inhibit the degradation of thiocyanate and cyanide,and thiocyanate and cyanide can inhibit the degradation of ammonia nitrogen.The main organic pollutants in the influent water are ethyl propionate,phenol,neopentyl glycol,2,2-diethyloxypropane,ethyl butyrate,2,2,4,4,6,8,8-heptanonane and ethyl benzoate.After SMBBR treatment,2,2,4,4,6,8,8-heptanonane,ethyl butyrate,ethyl benzoate and phenol were completely removed.The high-throughput sequencing technology was used to monitor the evolution of biofilm bacterial community structure and analyze the response relationship between pollutant degradation and the change of biofilm bacterial community structure.CCA was used to analyze the influence of environmental change caused by pollutant degradation on the structure of biofilm flora.The results showed that the abundance and diversity of biofilm flora were different with different reaction time.During the reaction period,Proteobacteria had the highest relative abundance(20.57%~34.55%),which promoted the degradation of phenol;Thauera,ottowia and unclassified_o_rhizobiales were the dominant bacteria of phenol degradation in the system,Thiobacillus was the dominant bacteria of SCN~-and CN~-degradation.CCA analysis showed that pH value had the most positive correlation with Nitrospira,and effective control of pH value could contribute to the stable operation of nitrification.