Conditions Influencing Struvite Precipitation from Anaerobic Sludge Digestion Filtrate in a Batch Reactor

Abstract

Struvite precipitation in sludge dewatering filtrate was achieved in a lab-scale sequencing batch reactor. The influence of the operational conditions on the struvite precipitation process has been studied. These operational conditions include stirring rate of the reactor, reaction time and sedimentation time. Experiments indicated that stirring rate of the reactor within 50 rpm to 250 rpm had no strong influence on the formation of struvite. As reaction time increased, there was a slight positive effect on the removal of Mg2+, NH4+ and PO43-. Suggested reaction time is 40-80 minutes based on our experiments. In order to obtain the lower turbidity and the lower PO43- concentration in the decanting filtrate of the batch reactor, the minimum sedimentation time should be more than 30 minutes.