Environmental impact of polluted city canals — a case study from Colombo,Sri Lanka

The city canal of Colombo, an effluent canal running through the city, was monitored for its nitrogeneous species and toxic trace metal contents. The canal is the dumping ground for municipal garbage, human and animal excreta, organic waste matter, etc. However, nitrate content of the canal water remains low, indicating an incomplete nitrification process. Due to the existing pH and redox conditions, the nitrogen species are present in a chemically reduced form. Since the Pb, Cd, and Zn contents of the canal water are high, industrial contamination is obvious. The environmental impact of such a polluted canal is enhanced by the presence of a large number of drinking water wells in the vicinity of the canal.