Abstract
The successive extraction method with 0.1N HCl and 0.5N NH4OH for the analysis of organic phosphorus in soils was applied to determine the phosphorus in activated sludges from 24 sewage treatment plants in Chiba Prefecture. The repeatability of this method was satisfactory and the sum of the phosphorus in HCl and NH4OH extracts from the sludge was in agreement with the total phosphorus in the sludge which was measured after the digestion with H2SO4-HNO3.
The phosphorus content was higher in inorganic fraction in HCl extract and organic fraction in NH4OH extract than the other fractions. The inorganic phosphorus in HCl extract was considered the phosphorus which was accumulated by “luxury uptake” in the activated sludge and this phosphorus fraction was closely related to polyphosphates and metals such as Ca or Fe.
From the balances of phosphorus and sludge in an activated sludge process, the decrease of phosphorus concentration in the process was shown as follows : ΔP=aC' ΔBOD/ (1+bSRT) where C' was the phosphorus concentration in the microorganisms of the activated sludge. The amount of excess sludge per unit influent flowrate was found to be a factor controlling the phosphorus removal in an activated sludge process.
