Investigations On The Effects Of Methanol And Ethanol On Biological Phosphorus Removal In Sequencing Batch Reactor With Single-stage Oxic Process

In recent years, single-stage oxic SBR phosphorus-removal process gotgreat development because of its simple process, stable water out and low cost.Carbon source is one of the main factors that affected the biologicalphosphorus-removal system, so it is an important research topic to look forlow cost and good phosphorus removal external carbon source.We studied the effect of phosphorus removal in single-stage oxic SBRsystem using methanol and ethanol as carbon source respectively because bothtwo carbon source are cheap and common in industrial production. First, wecarried out methanol （for SBR1#） and ethanol （for SBR2#） as the sole carbonsource, and investigated the effects of them on the efficiencies of biologicalphosphorus removal in the single-stage oxic process, respectively. The resultsshowed that the average phosphorus removal contents and its efficienciesrespectively reached at6.56mg/L,52.63%in SBR1#and11.22mg/L,90.34%in SBR2#during the steady-state operation, when the concentration ofphosphorus in the water was about13mg/L. For a typical SBR cycle, withinaerobic period, the phosphate uptake rates could reach1.62and5.31mgPO₄³--P/gVSS.h in SBR1#and SBR2#, respectively. In addition, theeffluent phosphate concentration in SBR2#was below the detection limit. Andthe internal storage compounds were higher in SBR2#than that in SBR1#during a cycle. The results suggested ethanol as a carbon source seemed to bebetter for biological phosphorus removal in biological phosphorus removalsystem. During the idle period, more phosphorus was found to be released inSBR2#than that in SBR1#as more poly-p was degraded, due to the higheractivity of PAOs in SBR2#.In consideration of the good performance of ethanol’s phosphorusremoval effect in single-stage oxic SBR, Thus further, we investigated thephosphorus removal effect both in A/O process for SBR3#) and single-stageoxic SBR（for SBR4#）.At the same time,we operated both SBR3#（A/Oprocess） and SBR4#（single-stage oxic SBR） using ethanol as carbon source.During the50d’s steady-state operation, ethanol as carbon source, the averagephosphorus removal contents and its efficiencies respectively reached at10.47mg/L,80.36%in SBR3#and11.21mg/L,89.41%in SBR4#. For atypical cycle, the phosphate uptake content reached15.62mg/g and16.93mg/g respectively in SBR3#and SBR4#. And the content of phosphorus release wererespectively9.63mg/g and7.66mg/g and the phosphate uptake contentrespectively reached15.62mg/g and16.93mg/g in SBR3#（for A/O process）and SBR4#（for single-stage oxic SBR）. Also the internal material storage（PHA and glycogen） capacity were respectively3.29mmol/gå’Œ5.29mmol/g inSBR3#（for A/O process） and SBR4#（for single-stage oxic SBR）. The reasonwhy the internal material storage is more in A/O process and its phosphorusremoval effect is a bit poor is that the energy of its internal material storagenot only for P uptake but also for glycogen synthesis and large phosphorusrelease. In comparison, the internal material storage is mainly used in P uptakein single-stage oxic SBR process.We concluded that the phosphorus removal effect of ethanol is better thanmethanol in single-stage oxic SBR process, according to the experimentalresults. Further study shows that both single-stage oxic SBR process usingethanol as carbon source and A/O process had good phosphorus removal effect,but the phosphorus removal effect was better in single-stage oxic SBR processin comparison, which shows that this kind of process has great feasibility usingethanol as carbon source.