Abstract
In recent years, efficient enhanced biological phosphorus removal (EBPR) processes operating at temperature higher than 28 °C have been reported in several studies. However, the operating strategy to maintain stable and high phosphorus removal efficiency at tropical temperature remains elusive. In EBPR process, glycogen accumulating organisms (GAOs) compete with polyphosphate accumulating organisms (PAOs) for the often limited carbon substrates. Carbon loading is apparently impactful on the EBPR performance. Although there have been many studies on the effect of carbon concentration on EBPR, the temperature range investigated was below 25 °C. It is of our interest to elucidate how carbon loading affects the EBPR performance at higher temperatures. In this study, EBPR is carried out at 30 °C in a laboratory-scale sequencing batch reactor (SBR) with a working volume of 1.6 L. The seed sludge was obtained from a local sewage treatment plant (STP). The reactor was operating under alternating anaerobic-aerobic condition and fed with acetate-rich synthetic wastewater. The acetate concentration is reduced consecutively from phase I (60 mg C/L) to phase II (40 mg C/L). The reactor exhibited EBPR characteristics one week after the start-up, showing an extremely short acclimatisation period. In phase I, we observed an increase in the anaerobic phosphorus release from 61 mg P/L to 125 mg P/L and the aerobic phosphorus uptake from 28 mg P/L to 121 mg P/L. The phosphorus content in the dry biomass also increased from 3 wt% to 11 wt%. In phase II, the reduction of acetate concentration led to the deterioration of EBPR performance whereby the phosphorus content reduced from 11 wt% to 4 wt%. The findings indicate that higher carbon loading may be a key to maintain efficient EBPR processes in the tropics.
