下水汚泥からのリン溶出に関する実験的検討

抄録

The behavior of phosphorus in sewage sludge from various kinds of activated sludge processes was investigated by laboratory-scale experiments. Using an extract-fractionation method, insoluble phosphorus in sludge was divided into three fractions: the metal phosphate fraction, the polyphosphate fraction and the other fraction. In the experiments, more than 40% of insoluble phosphorus was rapidly transformed within 24 hours under anaerobic conditions to soluble phosphate in mixed sludge from an anaerobic-aerobic activated sludge process. In the sludge, the transformed phosphorus was originated from the polyphosphate fraction and the other fraction. On the other hand, only 16% of insoluble phosphorus was slowly dissolved over 72 hours in sludge from a conventional activated sludge process, because there are a less amount of phosphorus in the polyphosphate fraction and the other fraction than that in sludge from other activated sludge processes. Little phosphorus was dissolved when excess coagulants existed in sludge after added metal salts in activated sludge processes, because dissolved phosphorus from the polyphosphate fraction and the other fraction was converted to insoluble metal phosphate. From the experimental results, amounts of soluble phosphorus after 72 hours were recognized to have a close correlation with the molar ratio of metal component to phosphorus of the polyphosphate fraction and the other fraction at 0 hour.