The Study On Sludge Reduction Mechanism For SBR/OSA Process

This paper studied the efficiency of sludge reduction in the process of sequencing batch activated sludge reactor combined with anaerobic reactor(SBR/OSA process),a modified process of oxic-settling-anaerobic process(OSA process).SBR/OSA process was operated stably for 4 months in parallel with the control reactor which was no recycling anaerobic sludge.This experiment explored the water quality,the characteristics of both aerobic sludge and anaerobic sludge and the consequence of sludge reduction respectively.Meanwile,the main mechanism what influence the sludge reduction was also investigated.Throughout the experiment,the influent used domestic sewage added artificial carbon source.The organic sludge loading was 0.28?0.52kg COD/kgMLSSd.Sludge age of main reaction zone was 15d.Sludge age of anaerobic column was 7d.The removal results of sewage treatment in both systems were well under above operational conditions.The results showed that:(1)SBR/OSA process with the anaerobic sludge reflux had no significant difference on sewage treatment.Effluent could almost meet the requirement of A in first gradge discharge standard of GB18918-2002.TP removal rate was slightly higher.SBR/OSA system could improve sludge settling and adaptability to sudden change of organic load.(2)Ammoniation and hydrolytic acidification reaction occurd in the anaerobic column of SBR/OSA process.Concentration of COD?NH3-N and TP was increased significantly.Due to high concentration of anaerobic sludge,NH3-N and TP index was higher than the control group.COD growth of anaerobic sludge was slightly lower,indicating lower degradation rate of microbial death.In anaerobic column,the main growth component was VFA-oriented,small amount of protein and little polysaccharides production.(3)SBR/OSA system could reduce system sludge production effectively compared with the control group.Sludge reduction rate reached 32.29%.Observed growth yield of sludge was 0.084gMLSS/gCOD.Anaerobic column was the key cause of sludge reduction in SBR/OSA process.Anaerobic column led to reduce 0.22g/d sludge production resulted by sludge decay.SBR/OSA systems could reduce 56.67%sludge production compared with traditional SBR system.(4)Activated sludge in main reaction of SBR/OSA system was higher active.Decreasing the amount of organic matter in anaerobic column showed anaerobic column was primary cause of reducing sludge production.Amount of organic matter in sludge discharged daily from SBR/OSA system that was less than traditional SBR system and the control system.It suggested organic matter played a major role on sludge yield.(5)Because microbial in SBR/OSA system had adapted to the alternation of anaerobic-aerobic environment,MLSS decreased 19.15%in the control group and 14.12%in the SBR/OSA system after activited sludge anaerobic treated for 24h.It explained that low ORP and no outside energy could promote reduction of sludge.MLSS decreased 23.73%in the control group,but MLSS only decreased 14.30%in the SBR/OSA system after activated sludge anaerobic treated for 7d.It illustrated that sludge decay in anaerobic column not only related sludge properties,but also had something to do with sludge retention time.(6)In this experiment,the main reason of sludge reduction in SBR/OSA system is sludge decay,but had nothing to do with the uncoupling of energy.The range of sludge decay coefficient was 1.05?1.15.The existence of energy uncoupling was related to the residence time of anaerobic sludge.The reduction of sludge could be achieved 12.38%when the activated sludge anaerobic treated for 24h.It could be concluded that SBR/OSA system is not the longer the anaerobic sludge retention time,the better the sludge reduction efficiency.The technology of SBR/OSA sludge reduction process is simple and easy to operate.It just inserts the sludge storage tank without adding any chemicals based on traditional SBR technology.It can meet the sewage discharge standard and achieve the purpose of sludge reduction.The experimental results have a good reference value on application of this technology.