Modelling for organics and nutrients release during benthal sludge stabilisation part il - Nutrients

Abstract

Settleable solids from untreated or partially treated domestic and industrial effluents undergoing stabilisation in stream beds contain significant amount or nutrients such as ammonia and phosphates apart from carbonaceous organic material. An experimental investigation was carried out to study the contribution of biochemical oxygen demand (BOD) and nutrients by this benthal-sludge undergoing stabillisation in steam beds. Sludge was collected from a sewage channel and placed at the bottom of an experimental reactor, and a continuous flow of clean tap water was maintained, in such a manner that the sludge was not disturbed. The first part of this work contained a discussion on degreadation of carbonaceous matter. The degradation of the nutrients, such as ammonia and phosphates being released from the sediments into the overlying waters at different flow rates of over laying waters is evaluated. It was noticed that the ammonia and phosphates released from the sediments into the overlying waters become more or less uniform after some days. The ammonia release and phosphate release were found to be affected by changes in the flowrates of overlying waters. The ammonia and phosphates remaining in the top and bottom layers of the sediments also showed similar trends. Predictive models have been presented for the variation of ammonia and phophate release into the overlying water, ammonia and phosphates remaining in the sediment layers at different times and different flow rates.