RECOVERY OF BIOLOGICAL PHOSPHORUS REMOVAL AFTER PERIODS OF LOW ORGANIC LOADING

Activated sludge plants for enhanced biological phosphorus removal (EB PR) are often disturbed by short periods of low organic loading. Depen ding on the exact nature of the disturbance this may result in a parti al or complete depletion of the internal PHB stores. PHB and phosphate measurements in a pilot-scale EBPR process show that recovery from su ch disturbances is slow and temporarily results in high phosphate conc entrations. The measurements strongly suggest that the main reason for this slow recovery is a dependency of P-uptake on a slowly rising lev el of PHB. In a number of batch experiments this dependency of P-uptak e on PHB was clearly shown. Also, based on the results of these batch experiments, a more detailed analysis was made of the effect of organi c loading and aeration time on EBPR recovery. It is concluded that to obtain EBPR recovery, the aeration time should be carefully adjusted t o the organic loading, particularly if the organic loading is low. Cop yright (C) 1996 IAWQ.