The Effect Of PH And Carborn Source Concentration On Phosphorus Removal In Sequencing Batch Reactor With Single-stage Oxic Process

The study investigated the effects of pH and COD concentration on biological phosphorus removal in single-stage oxic SBR, using synthetic wastewater, with glucose as carbon source.When study the effect of pH on biological phosphorus removal, two lab-scale sequencing batch reactors (SBRs) were operated (R1:pH8±0.2; R2: pH7±0.2) using synthetic wastewater, and variations of the main intracellular polymer during a cycle were also compared to discuss the probable reasons for different performances of phosphorus removal. The results showed that both R1and R2performed well in phosphorus removal,94.9%and83.5%of the average efficiencies of phosphorus removal were respectively obtained in R1and R2, suggesting that the effect of pH on phosphorus removal was slight in such a single-stage oxic process. The reason for the higher performance of phosphorus removal in R1was its stronger dependence on polyphosphate. During the aerobic period, the accumulation of glycogen by bacteria in R1was lower than that in R2(R1:1.42mmol/g, R2:1.55mmol/g), but the degradation of glycogen in R1was higher (R1:1.41mmol/g, R2:1.19mmol/g); in the idle phase, glycogen in R2degraded obviously while that in R1seldom degraded. Besides, though obvious phosphorus release was observed in both R1and R2, the content of phosphorus released in R1was higher (R19.65mg/L, R27.33mg/L). A slight decrease and increase of PHA were respectively observed during the aerobic and the idle periods in R2while no obvious change of PHA was found in R1during the whole period.When study the effect of COD concentration on biological phosphorus removal, four lab-scale sequencing batch reactors (SBRs) were operated(R1200mg/L, R2500mg/L, R3800mg/L, R41100mg/L), using synthetic wastewater, the difference of phosphorus removal performances and the probable reasons for the difference were discussed. The results showed that41.60%,91.87%,65.93%and33.40%of the average efficiencies of phosphorus removal were respectively obtained in R1、R2、R3and R4, suggesting that the effect of COD on phosphorus removal was strong in such a single-stage oxic process. When COD increase in the system, phosphorus removal performance increased ininialy, then decreased and even crashed. In the aerobic period, glycogen accumulated in R1、R2、R3and R4were1.32mmol/g,3.16mmol/g, 7.25mmol/g and9.01mmol/g respectively; glycogen degraded in these reactors were1.30mmol/g,3.13mmol/g,3.01mmol/g and1.92mmol/g respectively. When COD increased from200mg/L to500mg/L, the reason for the increased phosphorus removal performance was ATP provided in related reactor increased; when COD increased from500mg/L to1100mg/L, the reason for the decreased phosphorus removal performance was the dependence on polyphosphate by microorganisms in related reactor weakened and even lost.