ROLE OF METALS AND PHOSPHATE CRYSTALLIZATION IN BIOLOGICAL PHOSPHORUS REMOVAL

Throughout the industrialized world regulators are pushing towards more stringent discharge standards for municipal, industrial, and agricultural wastewater treatment facilities. Meeting these standards requires more and more facilities to apply methods of nutrient removal. Amongst these methods, biological phosphorus removal is gaining popularity due to the potential for savings in chemical costs. Today, the mechanism of enhanced biological phosphorus removal (EBPR) is fairly well understood. Yet for many treatment plants that operate EBPR and anaerobic digestion, a number of significant interrelations exist, some of which may hold the key to success and level of phosphorus removal. The main interrelations include the uptake and release of phosphate, magnesium, potassium, and ammonia; corresponding crystallization reactions, calcium phosphate precipitations; solids processing recycle phosphate load; and the required load of readily biodegradable COD. This paper discusses some of the EBPR process optimization results and two years of operation experience at Durham Facility, Portland Tigard OR. While the facility has been delivering exceptional biological phosphorus removal results (