The Selection Of Mixed Predominant Bacteria By Coke-plant Wastewater And The Studying Of Their Degradation Ability

The composition of coking wastewater is very complex,which contains a large quantity of toxic and harmful substances and is a kind of typical refractory organic wastewater.The removal rate of the refractory organics by the conventional activated sludge process is low,which results in a relatively high value of COD,NH₃-N and chrominance in effluent,so the quality of effluent can not reach the national draining standard.In recent years,the scientific researchers have proceeded to extensive research,and then looked for the high-efficient,economic ways to dispose coke-plant wastewater,improved environment quality and realized water-resource recycle.This paper has recounted the origin,characteristic,mostly constituting, actuality and advance in the technology of treating coke-plant wastewater. Among the treatment of refractory organic wastewater,bio-augmentation has been discussed and applied in coke-plant wastewater.Therefore,selected the mixed predominant bacteria from the separated bacteria,studied their degradation capability in treating coke-plant wastewater to provide a way of biodegradation of actual wastewater.The mixed predominant bacteria were selected from six separated predominant bacteria,which were separated from activated sludge of aeration tank of the coke plant,by the turbidity of bacteria liquid and TTC-dehydrogenase activity.The mixed predominant bacteria are DPâ…¢_3a,DPâ…¢₁₆,EPâ…£₁,DPâ…¢₂₁,the proportion of bacteria is 2:2:1:1.Their growth characteristics have been primarily researched.The result indicates that the best cultivating time is 24 hours,the best temperature is 30～35℃and the best pH is 7～7.5 for the mixed bacterial growth.The degradation ability of the mixed predominant bacteria has been studied on a kind of cultivate conditions.The orthogonal experimental research result shows that it is the best cultivate condition,when temperature is 35℃,pH is 7, shaking culture is at 120r/min.All these conditions are favorable for the growth and reproduction of the mixed predominant bacteria.The coke-plant wastewater treatment system of conventional active sludge, of the mixed predominant bacteria cooperating with activated sludge,and of the mixed predominant bacteria immobilized with activated sludge using aggregation and cross linkage have been researched simultaneously.The results show that(1)The mixed predominant bacteria can accelerate the speed of domesticating the sludge and eliminate sludge expansion effectively.(2)The mixed predominant bacteria can obviously raise COD removal rate of coke-plant wastewater cooperating with activated sludge,the max COD removal rate can reach up to 73.5%,on average 68.6%,and it can be raised by 16.3%compared with conventional activated sludge.(3)The mixed predominant bacteria can further increase COD removal rate of coke-plant wastewater after immobilized with activated sludge,the max COD removal rate can reach up to 84.8%,on average 78.4%,and it can be respectively raised by 26.1%and 9.8%compared with single activated sludge and the mixed predominant bacteria cooperating with activated sludge.(4)The mixed predominant bacteria immobilized with activated sludge can dispose the chrominance as well,the max chrominance removal rate can reach up to 84.8%,on average 78.4%,the of effluent averagely fell to 100-fold.Combined with subsequent treatment,it can satisfy the country standard of GB8978-1996The experimental research results show that the mixed predominant bacteria cooperating with the activated sludge make for improving the removal rate of coke-plant wastewater compared with conventional active sludge.The disposal effects of the mixed predominant bacteria immobilized with activated sludge by using aggregation and cross linkage can also be improved further.It will be possible that the effluent COD and chrominance meet with the national draining standard.The testing result of this paper can offer the references for farther study and application.