Characteristic Contaminants Degradation And Microbial Community Succession Of Coking Wastewater

Coking wastewater is a typical industrial wastewater with high toxicity.Its main characteristic contaminants are volatile phenol,thiocyanide,ammonia nitrogen,PAHs,etc.Its treatment with biological processes is often challenging because it contains constituents inhibiting microbial activity.Most coking wastewater treatment processes use municipal sludge as the start-up sludge for domestication.In the activated sludge process,microorganisms are the key factors to determine the quality of sludge treatment.Therefore,The study on the composition of sludge microbial community can reveal the law of sludge evolution in the process of domestication,and provide the basis for regulating the process capability.This paper combines the A/O/H/O process,focusing on the process of domestication of municipal sludge in aerobic stage.And the process of domestication of sludge was obtained by investigating the degradation of pollutants and the changes of microbial communities.The main research contents and results are as follows:(1)The effects of A/O/H/O coking wastewater treatment on the degradation of COD,ammonia nitrogen,volatile phenol,cyanide and PAHs were investigated and compared with those of A/O2 process.The results showed that the removal rates of COD,ammonia nitrogen,volatile phenol,thiocyanide were 97.87%,96.73%,99.99%,99.16% and 99.72% respectively in A/O/H/O process.The removal rate of ammonia nitrogen and volatile phenol was higher than that of A/O2 process.The A/O/H/O process was more effective in the degradation of PAHs.The concentration of 16 PAHs in the effluent was only 3.52 ?g·L-1 and the concentration of BaP was 0.009 ?g·L-1.It was also found that PAHs were adsorbed in the sludge during the treatment,which was not conducive to the biodegradation of PAHs,indicating that the decrease of PAHs in the process may be the result of the interaction between microbial degradation and sludge adsorption.(2)To study the inhibitory effect and possible acclimation of microbes in coking wastewater treatment,municipal sludge was inoculated into coking wastewater.Time dependent concentrations of COD,phenol,ammonia nitrogen and thiocyanide in coking wastewater were analyzed.Microbial community structure was investigated by the Illumina high-throughput sequencing technology during inoculation.The results showed that COD began to decrease after 16 h and that 97.1% of phenol disappeared after 40 h.Thiocyanide began to be degraded at 72 h and was undetectable after 96 h.Accordingly,the concentration of ammonia increased as the thiocyanide concentrations decreased.High-throughput pyrosequencing analysis showed that the microbial community structures and species richness were different over different culture stages.In the stage of phenol degradation,the abundance of Acinetobacter and Pseudomonas increased rapidly,the two species richness were 13.04% of the community at 48 h.In the stage of thiocyanate degradation,Sphingobacterium,Brevundimonas,Lysobacter,Chryseobacterium were dominant bacteria and were 16.13% species relative abundance of community at 96 h.At 144 h,Fluviicola,Stenotrophomonas and Thiobacillus became the dominant species and were 22.45% of the community abundance.The results showed that municipal sludge can rapidly overcome the toxicity of coking wastewater as the pollutants were degraded rapidly.Microbial community structure changed as different wastewater components were degraded.It appeared that environmental factors and competition of bacteria played key roles in the microbial community succession.(3)In order to investigate the effect of glucose,phenol and Triton X-100 on the degradation of characteristic contaminants and the change of microbial community during the domestication of municipal sludge.The glucose,phenol and Triton X-100 were continuously flowed during the process of municipal sludge acclimation and measured COD,ammonia nitrogen,thiocyanide,total nitrogen and PAHs.The effects of three kinds of flowers on the reaction system were analyzed by combining the changes of characteristic pollutants and microbial community test results.The results show that all the four reaction systems can effectively degrade COD and thiocyanide in coking wastewater.The results of community sequencing showed that 80% of the microbes in the four reaction systems belonged to Proteobacteria,but in the genus level analysis,there were significant differences in the four reaction systems.The study also found that the reaction system with glucose and phenol had good ability to degrade ammonia nitrogen and total nitrogen.However,from the practical application,phenol was the main component of wastewater,so the application of phenol was more practical.In addition,the degradation efficiency of PAHs,the reaction system with Triton X-100 was higher than that of the other two reaction systems,and Alcaligenes,Diaphorobacter,Sphingobium,Sphingopyxis and Stenotrophomonas(PAHs degrading bacteria)were present in the reaction system with Triton X-100.It is shown that the addition of Triton X-100 in the process of municipal sludge acclimatization can effectively improve the degradation ability of PAHs.