Benthal sludge stabilization in the river Ganga at Kanpur: Part I - Field observations

Abstract

Field observations were conducted at Kanpur to analyze the ration of biochemical oxygen demand (BOD) contributions by benthalsludge to the overlying waters of the river Ganga. This data was later correlated to the data obtained under different conditions of operating and process variables in the laboratory. Observations were made at 3 sections along the river downstream of an outfall discharging partially treated wastewater. The rate of BOD contribution by benthalsludge to the overlying waters was estimated by utilizing the observed values of dissolved oxygen (DO) and BOD and is presented in Part 2 of this paper. The rate of BOD contribution was higher at section A during summer and at section B during winter, throughout the depth of overlying waters. This is because of the higher stabilization of the settled organic matter during summer. In winter, the BOD released gets carried away to the downstream sections. The rate of BOD contributions (expressed as a percentage of the BOD remaining in the top benthalsludge layers) was insignificant during winter. The rate of BOD contribution (expressed as a percentage of the BOD added continuously) was higher at sections closer to the outfall during summer, but higher at section B in winter. Predictive models were developed for the rate of BOD contribution by benthalsludge. The observations in the laboratory were done on a significantly smaller model and the field data differed by an order of magnitude. Models were developed to predict the overall scale factor (OSF) for different field conditions by benthalsludge by using the laboratory models. 2011 - Kalpana Corporation.