When a town grows into a city, or when many towns and cities are built along the same river, the #ecosystem is overwhelmed by the large amount of #wastes. So #sewage treatment becomes absolutely necessary. Modern sewage technology shows an understanding and application of part of the #aquatic ecosystem. Sewage treatment plants for instance, utilize the same microorganisms that serve as decomposers in natural bodies of water. But as #urban growth and #population have continued to increase, it has become apparent that sewage treatment technology is only partly in tune with the ecosystem. However, the nitrates, phosphates and other nutrients released from the organic matter by the #microorganisms in the sewage treatment plants are passed on through the ecosystem where they stimulate the growth of #algae. Thus, the end result is #eutrophication. Algae overgrowth has been a major factor, for instance, in the break down of the ecosystem in some of North America’s lakes such as the #Lake Erie