The Impact of Organic Contamination on the Dynamic Equilibrium of Dissolve Oxygen in Selected Water Bodies in South East Sri Lanka

Abstract

Domestic and other related waste disposals lead to degrade the rate of equilibrium ofdissolved oxygen (DO) in the water bodies. The aim of this study is to investigate thecontributions of the organic contamination throughout the measured parameters of dissolvedsulfide, chemical oxygen demand (COD), nutrient level and salinity in dynamic equilibriumof DO. The selected parameters were observed over a period of six month and thecorrelations were studied among them for randomly selected two water bodies (WB) withdifferent type of waste effluents. Results indicated that the measured DO has good negativecorrelation with COD (r2 > 0.8), dissolved sulfide and nutrient levels in the both stationsimplies a strong impact on the dynamic equilibrium of DO. Also, the measured DOdemonstrated poor negative correlations (r2 < 0.5) with salinity indicate salinity as a lessimportant parameter for the dynamic equilibrium of DO.

The measured data were utilised in estimating the oxygen transfer efficiency, α and β values.Particularly, in Karaivahu (WB) and Allai (WB) exhibited low levels of partial pressuresimply higher level of α and lower β values. However, which were found to be in the range of8.67 – 16.88 and 0.99 – 1.02 respectively. The nutrient and COD values were observed in therange of 0.0 - 10.0 mg/L and 0 - 900 mg/L respectively. This concluded that the COD levelsignificantly contributes to the variation of DO throughout the surface active substance in thewater bodies.