Modelling for organics and nutrients release during Benthal sludge stabilisation : Part I -organics

Abstract

Settleable solids in the untreated and partially treated domestic and industrial effluents discharged into a river system undergoes settling and decomposition in the form of benthal sludge deposits, Early models of biochemical oxygen demand (BOD) assimilation in rivers do not account for the BOD contribution by these benthal sludge deposits. In this paper, a model for computations of the BOD contribution by benthos (both from the top aerobic layers and the leached portion of BOD from the bottom anaerobic layers) was presented. Observations from three sets of experiments at the chosen overlying water flow rates (500 ml/min, 1000ml/ min and 1500 ml/min) show a higher BOD contribution by benthos at higher overlying water flow rates. The ratio of the BOD contributions by benthos to the volatile solids in the top aerobic layers was lower when compared to the similar ratio in respect of the bottom layer volatile solids showing that a higher contribution was made by the top layers.