BIOMASS CHARACTERIZATION IN A NITRIFICATION-DENITRIFICATION BIOLOGICAL ENHANCED PHOSPHORUS REMOVAL (NDBEPR) PLANT DURING START-UP AND SUBSEQUENT PERIODS OF GOOD AND POOR PHOSPHORUS REMOVAL

During commissioning and process stabilization of a NDBEPR plant at Be ndigo intracellular distribution and movement of phosphorus, K+, Mg2and Ca2+ was followed to establish the nature of biomass development. The system was also monitored at the end of a period of breakdown of t he BEPR process and during its return to phosphorus removal. Phosphoru s (P) and Mg2+ distribution in the biomass were closely related during all phases of plant operation, and laboratory trials indicated that t he poor performance of the full-scale plant was associated with season al reduction in influent Mg2+. Laboratory scale trials produced a simi lar effect when the influent Mg2+ was limited to concentrations much l ower than those experienced in the full scale plant, but only after th e Mg2+ and P reserves in the biomass were depleted. The distribution o f P, K+, Mg2+ and Ca2+ in the biomass from the full scale plant was si milar to that seen in the laboratory trials when cations in the feed w ere severely limited and recovery of the full scale plant also closely matched that of the laboratory scale system.