Deoxygenation andReaeration Coupled hybridMixing cells Based Pollutant Transport Model to Assess water Quality Status of a River

Document Type: Original Research Paper

Author

Civil Engineering Programme, School of Engineering, University ofKwaZulu-Natal, Durban 4041, SouthAfrica

Abstract

Prediction of spatial and temporal variation of water quality is vital for managing pollutants
disposal into the rivers. Depletion of dissolved oxygen (DO) takes place due to the consumption of oxygen by
microbes to digest bio-degradable pollutants which enter a water course. Reaeration takes place in a specific
rate depending on DO deficit. Many investigators have formulated models as an alternative to the Fickian
Model for the advection dispersion pollutant transport. Since Streeter-Phelps research on BOD-DO modeling,
many researchers have studied fate of pollutant considering first order reaction along with only advection. The
Streeter-Phelps dispersion model includes deoxygenation and reaeration along with advection and dispersion
and which has been solved by defining an axillary variable relating DO deficit and BOD concentration. Thus
this paper considered first order decay and reaeration along with advection and dispersion to simulate spatial
and temporal variation of DO concentration using a hybrid mixing cells model. The proposed model has been
successfully applied for a hypothetical flow conditions and the River Brahmani, India. River flow requirement
and regulation for pollutant disposal with pre-treatment were optimized using the responses of proposed
model for this River. This research analyzed the selected river reach using proposed model having a particular
flow and channel characteristics and found that release of 1180m3/s from Rengali Dam is required to avoid
pollution problem. However, in absence of this flow at least 50% of pretreatment pollutants are required
before released into river Tikira.

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