Effect of Ph and SRT on Denitrifying Phosphorus Removal in A2n Sequencing Batch Reactor Process

Abstract

This research investigates the effect of pH and sludge retention time (SRT) on denitrifying phosphorus removal. A series of experiments were conducted using two 20L sequencing batch units with the following configuration: anaerobic/anoxic and aerobic sequencing batch reactors (SBRs). It was found that variation in pH form 6.5 to 8 resulted in obvious increase in phosphorus release and uptake, organic matter degradation [measured by the chemical oxygen demand (COD) and the percentage volatile suspended solid (VSS)] and polyhydroxybutyrate (PHB) accumulation also showed a rising trend in the anaerobic period, but sludge acclimatized under pH 8.5 condition exhibited a slightly lower denitrifying phosphorus removal capability. In addition, the rates of phosphorus release and uptake were 20.95 and 23.29 mg/g VSS / h in condition of pH 8 value. Activated sludge with the SRT of 16 days possessed better nitrite nitrogen utilization, organic matter degradation and phosphorus removal than sludge with the SRT of 6, 10 and 22 days, and polyphosphate concentration in anaerobic activated sludge per VSS decreased to 23.1 mg/g VSS, PHB concentration in anoxic activated sludge per VSS reduced to16.3 mg/g VSS, thus, a dramatic denitrifying dephosphatation has occurred.

Improved Biological Phosphorus Removal under Low Solid Retention Time Regime in Full-Scale Sequencing Batch Reactor

“…A study on the activated sludge-treatment process suggested that activated sludge with an SRT of 16 days acquired better nitrite nitrogen utilization, organic matter degrada-tion, and phosphorus removal than sludge with an SRT of 6, 10, and 22 (days); polyphosphate concentration in anaerobic activated sludge per volatile suspended solids (VSS) decreased to 23.1 mg/g VSS; and poly-β-hydroxy butyrate (PHB) concentration in anoxic activated sludge per VSS was reduced to 16.3 mg/g VSS; therefore, a spectacular denitrifying phosphate removal occurred [5,6]. However, another study investigated the effects of SRT on sludge characteristics and operational performance in an EBPR reactor in which the results showed that the reactor operated at SRT of 8.3 days could achieve a phosphate removal efficiency of >90% and a sludge volume index (SVI) of <100 mL g −1 [7].…”