Assessment of Dissolved Pollutants in Krishna River Using Mass Balance Approach

Abstract

The River Krishna in Andhra Pradesh is typical receiving water body for urban and rural runoff. The river shows strong seasonal dependence for various constituents and the water quality deteriorates sharply as municipal and Industrial wastes are joining the River Krishna. The important characteristic associated with the pollution of the river is the slightly reduction of self-purification process over a stretch of about 85 km. A chemical mass balance approach has been used for measuring changes in the concentration and/or load to the river, which in turn calculates the transport of pollutants. The mass balance calculations conducted for certain water quality constituents indicated that additional inputs are needed to account for the observed differences in load along the river. The sources may include non-point sources of pollution due to agricultural activities, sediment remobilization or entrainment, ground water intrusion or a combination of these sources. Mass balance calculations over a 4 years period indicate that pollutants are retained in the sediments of the investigated 85-km long reach of the stream (2,500 kg of Potassium, 40,000 kg of Sodium, 25,000 kg of Chloride, 2,000 kg of Fluoride and 2,000 kg of Silicates). Other pollutants such as Calcium, Magnesium and Sulphate appear to retained and washed-out, depending on leading rates and local stream conditions. The retained pollutants represent a substantial part of the total mass transport through the stream (10–75%). Almost 80% of the transported Potassium is retained within the stream sediment. Subsequently, the deposited pollutants represent a potential pollutants source.