Sustainable Water Engineering: Theory and Practice

6 Sustainable Effluent Disposal

Pollution can occur due to natural contamination, like poison springs and oil seepage, or due to anthropogenic contamination. The sources could be point (ditches, drain pipes, or sewer outfalls) or nonpoint pollution sources (runoff from agricultural fields/feedlots, lawns, gardens, golf courses and atmospheric deposition of air pollutants carried by air currents). One of the most serious concerns about water contaminants in terms of animal/human health is pathogenic organisms that originate from untreated or improperly treated wastes. Water bodies with clear water and less biological productivity (oligotrophic conditions) are often converted to eutrophic conditions, which are rich in organisms and organic materials. Human activities have greatly accelerated eutrophication, leading to imbalances in nature. High biological productivity is seen in ‘blooms’ of algae and dense growth of aquatic plants. Blooms of deadly microbes called dinoflagellates have become increasingly common in many surface-water bodies, resulting in red tide. Pfiesteria piscicida, a poisonous dinoflagellate, which has wiped out millions of fish in polluted surface water bodies. Some toxic chemicals released from rock weathering are transferred by runoffs and anthropogenic activity can increase the rate of release of such inorganic chemicals by mining, use, processing and discarding of minerals. Rivers carry sediment to the oceans and human activities have greatly increased ...