Chemical and Microbial Contamination Status of Ground Water Quality in Kelani River Basin

Abstract

Water is the key factor in sustaining human life. Water pollution may occur in various formssuch as catchment characteristics, anthropological activities, land use practices and industrialdischarges. Such polluting agents may affect physical, chemical and biological parameters ofsurface and ground water. The present study was focused to analyse the present status ofground water pollution in the Kelani river basin by means of physico-chemical andmicrobiological parameter using standard analytical and microbial methods. Pesticides weredetected using pesticide library in the GCMS. Thirty ground water samples from head,transitional and meandering zones were collected for a period of six months from November2012 to April 2013. pH values of most of the samples were deviated from the SLS drinkingwater standards and remained acidic during the study period (3.98-6.46). 80% of samplesrecorded high COD values (12.81-307.19 ppm) and also showed an increasing tendencytowards downstream of the river basin. High BOD values were detected in meandering zone(4.80-10.19 ppm) in comparison to the head and transitional zones. The conductivity, TDSand hardness values were ranged between 21.67-917.00 μs/cm, 13.37-596.05 ppm, 2.00-206.67 ppm respectively. Acceptable concentrations of phosphate and nitrate were detectedbetween 0.004-0.344 ppm and 0.01-1.394 ppm. Total coliform and feacal coliform countswere almost above 1,100 for 100ml. Samples from head and meandering zone of the riverbasin have shown more than 80% and 100% of total and feacal coliform contaminationsrespectively. Heavy metals such as Cd, Al, Zn, Pb, Cr, Cu remains within the SLS standardsfor drinking water. During the rainy season in some sampling locations of the head andmeandering zone of the river basin, high Cd, Al and Zn were detected, though theconcentrations remain below the SLS drinking water standards. Some pesticides/derivativesnamely O,O-dimethyle S-methylcarbamoylmethyl phosphorodithioate, 5-bromo-3-sec-butyl-6-methyluracil, O,O-dimethyl S-2-(1-methylcarbamoyl-ethylthio) ethyl phosphorothioate, 1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)-2-butanone were detected in somewells in the transitional zone indicating the effect of anthropological activities on groundwater pollution in the Kelani river basin. The study is in progress to identify and quantifypathogenic microbes contamination in the river basin.