CALCIUM PHOSPHATE PRECIPITATION IN A DENITRIFYING BIOFILM — THE CONCEPTUAL BASIS

ABSTRACT A kinetic model for calcium phosphate precipitation in a fixed denitrifying biofilm is presented. The calcium phosphate precipitation is a result of the high pH created in the biofilm by the denitrification reaction. According to the model the phosphate removal is directly linked to the zero-order nitrate removal. In addition the removal rate is predicted to be relatively high in areas with low alkalinity wastewater. If calcium carbonate precipitates and exists in equilibrium in the biofilm calcium phosphate will redissolve. The theory presented may explain some of the observations often referred to as luxury phosphate removal.