Biodegradation Characteristics Of Yeast And Kinetic Analysis Of Substrate Biodegradation By Sequencing Bath Reactor In Cassava Alcohol Wastewater Treatment

Targeting the removal of high organic matter,high total suspended solid(TSS)and complex component of cassava alcohol wastewater,the combination process of yeast and sequencing bath reactor(SBR)was studied in this paper.The biodegradation characteristics and some major factors influencing the COD removal rate in yeast treatment were investigated.Also,the work conditions and kinetic analysis of SBR post-treatment were studied.This paper aims at studying the feasibility of cassava alcohol wastewater treatment using the combination process of yeast and SBR,so as to offer the basis for engineering design.The COD concentration of cassava alcohol wastewater ranged between 14,660 and 30,140mg/L,BOD₅ concentration was in the range of 7,000～14,467mg/L.After yeast pretreatment,the COD removal rate could reach 83.2%to 86.4%,and the BOD₅ removal rate was ranging from 91.4%to 92.2%.Operating the experiments on a pilot scale continuously, the optimal controlled parameters were as follows:inoculation amount 1%o(v/v,the live bacterium was 4.1×l0⁶per milliliter),dissolved oxygen 2～3mg/L,influent pH 5.0～5.5, temperature 30℃,aeration time 72h,BOD₅:N:P was equal to 400:2:1.Due to the high organic content in the influent,after yeast pretreatment,the effluent COD concentration was in the range of 2,000～3,500mg/L.In order to ensure that the effluent would meet the National Standard for discharge,the effluent which was pretreated by yeast need to be combined with a post-treatment.The results of integration water-quality experiment and microorganism respiration rate experiment revealed that the BOD₅/COD ratio of wastewater pretreated by yeast was about 0.3,the wastewater was easy to be biodegraded,so the SBR could be applied to the post-treatment.Effluent was treated by SBR for 6 hours,and its COD concentration was reduced to less than 100mg/L.The optimal running parameters were as follows:restricted aeration,0.375m³/h of aeration rate,unadjusted pH,20minutes fill time,6hours aeration time, 20minutes settling time,20minutes decant time,and no idle time.It took 7 hours for each cycle to run.The kinetic analysis of substrate degradation in SBR was studied under optimal conditions.The results showed that the rule of organic biodegradation complied with the Monod equation under constant temperature;the non-biodegradation value was 63mg/L;the decelerated increment velocity constant was 0.0024.When the kinetic equation was used,the results showed that the practical treatment time matched with theoretical treatment time,and the formula derivation of organics biodegradation model was proven.Using the combination process of yeast and SBR in the cassava alcohol wastewater treatment,the COD and BOD removal rates reached 99%;the effluent COD concentration was reduced to less than 100mg/L,which complies with Grade one of the National Standard (GB8978-1996)for discharge.The optimal running parameters of yeast and kinetic model of SBR were crucial to the engineering design of cassava alcohol wastewater treatment processes.