Characteristics of Denitrifying Phosphorous Removal in AnaerobicAnoxic SBR System

Simultaneous biological phosphorous and nitrogen removal was investigated in an anaerobic/anoxic sequencing batch reactor (A/A SBR) enriched with denitrifying phosphorous removing bacteria (DPB) sludge. The lab-scale experiments were conducted under the conditions of various SRTs (14d, 60d, and 34d), COD concentrations (200 mg/L, 400 mg/L, and 600 mg/L), and nitrate concentrations (60, 80, 100 mg/L). These key factors had significant impact on the performance of the denitrifying phosphorous removal system. The results indicated that SRT set as 34d was favorable for the denitrifying phosphorous removal system. An increase of COD concentration from 200 mg/L to 600 mg/L led to the increase of anaerobic phosphorous release, but excessive residual organics in the anoxic stage inhibited phosphorous uptake. Anoxic phosphorous uptake increased with an increasing nitrate concentration under a threshold level. When nitrate concentration in the system was limited, secondary phosphorous release appeared.