Effect Of Temperatures On Nitrogen And Phosphorus Removal In Aerobic/Extended-idle Regime

In this paper, four temperature gradients(R1=5℃, R2=15℃, R3=25℃, R4=35℃)were introduced to investigate the effect of temperature on biological nitrogen andphosphorus removal in aerobic/extended-idle regime, in addition, sodium propionatewas adopted as the sole carbon source in synthetic wastewater. During the long-termoperation in four SBRs, sludge settleabilities kept good, effluent phosphorusconcentrations were averagely4.05,2.17,1.34and0.11mg/L with the corresponding61.5%,79.3%,87.2%and99.0%phosphorus removal efficiencies, and thephosphorus removal rates were0.501,1.432,2.538and3.700mg-P/(g-VSS·h),respectively. The results showed that increasing temperature could contribute tophosphorus removal. In addition, the activities of polyphosphate kinase andexopolyphosphate were0.093,0213,0.376,0.549U and0.010,0.019,0.029,0.025U,respectively, and the rates of phosphorus uptaking and releasing increased, whichindicated that temperature could impose the activities of polyphosphate kinase andexopolyphosphate, thus affecting the phosphorus removal. During idle period,contents of glycogen and poly-β-hydroxyalkanoates kept stable, while poly-phosphatebecame the main energy source, leading to the phosphorus releasing contents were1.95,6.42,9.90and9.56mg-P/(g-TSS), respectively. Thses results implied that theincreasingly temperature could promote poly-phosphate degradation to provide moreenergy, thereby achieving better phosphorus uptake. It is clear thatAerobic/Extended-Idle Regime has a good application prospect of phosphorusremoval.Meanwhlie, the average efficiencies of ammonia removal were22.7%,98.9%,99.9%and99.5%, respectively. Moreover, the effluent nitrite concentrations did notexceed1.0mg/L in all reactors, and the effluent nitrate concentrations were2.59、6.01、8.30and7.70mg/L, respectively. These caused the average efficiencies of totalinorganic nitrogen removal were15.67%、82.17%、76.69%and76.95%, respectively.The results demonstrated that low temperature could seriously inhibit nitrogenremoval, however, nitrogen removal would perfectly meliorate when temperatureincreased. Nevertheless， the great reduction of total inorganic nitrogen withincreasingly temperature proved denitrification reacted obviously in aerobic period.Futhermore, the rates of nitrification were0.0187,0.0732,0.0905,0.1001mg-NH4+-N/(g-VSS·min), and the rates of denitrification were0.0022,0.0062,0.0080, 0.0095mg-NO3--N/(g-VSS·min), respectively. The phenomenon implied thattemperature could influence the activities of ammonia monooxygenase, nitriteoxidoreductase, nitrate reductase and nitrite reductase, accordingly affecting the ratesof nitrification and denitrification, then further influenced the nitrogen removal. Inthis experiment, the optimum temperatures of ammonia oxidizing bacteria, nitritebacteria, nitrate bacteria and denitrifying bacberia were15℃-35℃,15℃-35℃,25℃-35℃and about35℃, respectively. Nitrogen removal destruction at lowtemperature need to be improved, but nitrogen removal has a better potential appliedability in higher temperature environment.