The Study On The Removal Of COD In Coke Plant Wastewater By SBBR

The coke plant wastewater is characterized by its high concentration of COD,NH₃-N and poor biodegradability,large quantity of strong toxicity.if the wastewater was discharged in to water body without treatment,it could cause severe environment problems and also do harm to people's health,under the circumstances of coke sewage being drainaged without reaching standard in majority of coke factories,we adopted a process of biological way called SBBR to treat the wastewater.it is a new process which has many virtues,such as high efficiency,low consumptions and so on.The experiment included the performance and efficiency of the removal of COD.The conclusion was divided into two parts:First the start up of the systemThe stage of immobilization kept about 8 hours under the conditions of DO being 4.3-5.2mg/L and temperature being 25-27℃.at the end of the stage,the effluent COD reached 37mg/L,the removal rate was 92.6%.The second part of the start up work is to acclimatize high-efficient microorganisms.The influent COD concentration was 20%,30%,40%,70%。Considering biodegradable matters in coke sewage,we finished this part when the effluent COD reached 525.5mg/L and the removal rate was 85.0%.Second the examinations of the influencing factors of the removal of COD(1)In a whole period experiment,it is important for the COD removal result to make sure the time span of aerobic and anoxic stages.The experiment was done in one period to study the relationships when the influent COD concentration was about 1000mg/L and 1500mg/L.at the beginning,the removal rate of COD increases with extending the aerobic stage.It reached the best efficiency when the time of the aerobic stage was 8 hours,considering other factors,we thought a proper aerobic time in one period was 8 hours.(2)We inspected the removal rate of COD in one cycle and got the result: the removal rate changed when lengthened the reaction time.(3)We have studied on the relationship between the removal efficiencies of COD and PH value,it is the conclusion that the removal rate reached maximum when PH value was about 8.5 and decreased when PH value was 8.5-9.2.(4)The study was done with the influent COD concentration being about 1003.0mg/L,1241.3mg/L,1512.7mg/L,1757.1mg/L,2011.6mg/L and HRT being 12h,24h,36h,.48h,72h.The results were:When the HRT was less 48h,the COD removal rate increased with the increased HRT:when the HRT was more than 48h,the removal rate of COD became stable.Although the COD all having reached the number below 150mg/L,the reactive time extending with increasing influent COD concentration. (5)The experiment about effection of capacity loads to efficiency of SBBR showed:the COD removal rates increased with the increasing of COD loads was under 1.38kg/m³d and the maximum COD removal rates reached 92.5%;COD removal rates decreased with the increasing of COD loads when COD loads was over 1.38kg/m³d.it believed that 1.38kg/m³d was best at present experimental conditions.(6)The study was also done on the stability of the system in different influent COD concentrations.the results indicate:the removal rate all reached about 92%,it changed little when increasing the density of COD;the system had certain ability to resist the changes of COD loads.(7)We do the experiment in the optimum process conditions(HRT=48h,T=25-27℃,DO为4-5mg/L,PH=8.5),the results were:up to 94.5%of COD was removed and the effluent concentrations for COD were 94 mg/L-158 mg/L。it is considered that the COD could attained the primary and secondary national standard about wastewater discharge《GB8978-1996》when the influent concentration for COD was less than 2650 mg/L.