Tuesday, August 5, 2008
Organic wastes such as sewage impose high oxygen demands on the receiving water leading to oxygen reduction with potentially severe impacts on the whole eco-system. Industries release a variety of pollutants in their wastewater including heavy metals, organic toxins, oils, nutrients, and solids. Discharges can also have thermal effects, particularly those from power stations, and these too decrease the available oxygen. Silt-bearing overflow from many activities including construction sites, deforestation and agriculture can inhibit the penetration of sunlight through the water column, restricting photosynthesis and causing blanketing of the lake or river bed, in turn damaging ecological systems.