Treatment Efficiency And Fate Of Quinoline In A/O-MBR Process Treating Artificial Coking Wastewater

Coking wastewater is a kind of waste water which is inevitable in the process of industrial production such as gas purification and coking.The water contains a lot of different toxic and harmful substances.The traditional method is difficult to remove and purify it.China economic strength continues to grow,and theiron and steel enterprises developed rapidly,which discharged a large number of industrial wastewater,leading to the increasingly serious harm to theenvironment.Therefore the state enacted gradually strict laws and regulations.National put forward new requirements and policies for energy-saving emission reduction during the 12th five-year-plan period.However,using traditional technology to deal with coking wastewater is not only difficult to meet the national standards,but also the energy consumption is quite great.Therefore,the purpose of this study is to find efficient and stable energy-saving treatment technology of simulated wastewater,and to provide theoretical and technical support for improving the performance of the acttual coking wastewater treatment plant.In this study,the concentration of quinoline was about 200 mg/L,the concentration of phenol was about 100 mg/L,and the concentration of ammonia was 180 mg/L,COD concentration of 800-1200 mg/L in the simulated coking wastewater,anoxic/aerobic-membrane bioreactor(A/O-MBR)was used to achieve ammonia nitrogen,phenol and quinoline degradation.The effects of three parameters such as hydraulic retention time(HRT),dissolved oxygen(DO)and temperature on the removal efficiency of pollutants were investigated.At the same time,the structure of major microbial flora in the reactor was monitored by deformation gradient gel electrophoresis(DGGE)biotechnology,and the main functional flora in the reactor was clarified.Finally,the regression law of quinoline was analyzed by batch test.The main conclusions are as follows:(1)When the HRT decreased from 3 d to 1 d,the average degradation efficiency of phenol was about 99.0%,the average degradation efficiency of quinoline was about 98.0%,and the average COD degradation efficiency was about 94.0%.Ammonia nitrogen and total nitrogen removal efficiency were significantly decreased,ammonia nitrogen removal efficiency decreased from 99.4%to 28.6%,total nitrogen removal efficiency decreased from 89.1%to 21.0%.DGGE analysis showed that the main functional bacteria in the reactor were Aquamicrobium,Acinetobacter,Proteobacteria,Flavobacterium,Thauera,Solitalea and Hyphomicrobium.(2)When the DO declined from 1-3 mg/L down to 0.5-0.9 mg/L,the system on the COD removal efficiency was 92.0%,phenol and quinoline removal efficiency reached 98.0%.The removal efficiency of ammonia nitrogen was about 98.0%,and the removal efficiency of total nitrogen was increased from 81.1%to about 87.0%.DGGE analysis showed that the main functional bacteria isolates in the reactor were Comamonas.Acinetobacter?Delftia?Hydrogenophaga.The effect of DO on the biota in the reactor is mainly manifested in the increase of the biota in the aerobic zone,such as phenol degrading bacteria and short-term nitrifying bacteria.Under this condition,the sludge in the reactor can achieve the treatment of simulated coking wastewater and successfully achieve short-term nitrification.(3)When the temperature decreased from 32 ? to 20 ?,the removal efficiency of ammonia nitrogen from simulated coking wastewater decreased from 83.3%to 1 1.7%,and the removal efficiency of TN decreased from 69.5%to 7.8%.The degradation efficiency of phenol and quinoline was excellent,and the degradation efficiency was about 98.0%.The results of SEM showed that the decrease of temperature leads to the increase of extracellular polymeric substance and inhibited the activity of ammonia nitrogen flora,resulting in the decrease of ammonia nitrogen removal efficiency.DGGE analysis showed that the main functional bacteria isolates in the reactor were Aquamicrobium,Advenella faeciporci,Comamonadaceae,Trichococcus,Ottowia and Sphingobium.(4)When the temperature decreased from 32 ? to 20 ?,the volatilization efficiency of quinoline in aerobic zone decreased obviously,and the volatilization efficiency decreased by nearly 2 times.The degradation efficiency of quinoline decreased obviously.Degradation efficiency of aerobic zone decreased nearly 11 times,the anoxic quinoline degradation efficiency decreased nearly 9 times.When the temperature is 32 ? and 26 ?,the Freundlich isothermal adsorption curve can better fit the quinoline adsorption capacity of the activated sludge.When the temperature at 32 ?,26 ?,20 ?,the volatilization of quinoline accounted for 3.2%of the total daily quinoline,2.1%,1.6%;discharge accounted for 0.002%of the total daily quinoline,0.4%,0.02%;the amount of degradation accounted for 96.7%,97.1%and 94.4%of the total daily quinoline;the residual amount of water accounted for 0.2%,0.4%and 4.0%of the total daily quinoline.