Abstract
Relatively high ammonium concentration suggested nitrification inhibition in the pond water of a sea-based solid waste disposal site (SWDS) where incineration ash from municipal wastes is mainly disposed. Depletion of phosphate seemed to affect nitrification in the pond water. Very low concentration of phosphate in the pond water was attributed to the formation of relatively insoluble precipitates with salts contained in the incineration ash such as calcium. To elucidate phosphate deficiency in nitrification, an experiment was carried out in a pilot plant using fibrous contactor as the base of nitrifying biofilm. Addition of phosphate enhanced nitrification even at low temperatures under 10 ℃ while intermission of phosphate addition retarded nitrification even at temperatures above 25 ℃. Phosphate depletion was the primary factor in limitation of nitrification while no such limitation by depletion of inorganic carbon (IC), as an indicator of carbon dioxide or alkalinity, was observed under our experimental conditions. Accumulation of nitrite in the effluent of nitrification tank under low phosphate concentration suggested that nitrite-oxidizing bacteria (NOB) were more sensitive to phosphate depletion than ammonia-oxidizing bacteria (AOB). This implies applicability to partial nitrification by controlling phosphate supplementation.
