The labels usually also give first aid instructions. Read the label to find out how to use the product safely and what precautions to take for its disposal. Sewers collect the liquid waste and discharge it into lakes, streams or the ocean. Regardless of the process, sewage treatment plants concentrate the sewage into a solid called sludge, which is then utilized on agricultural land, disposed of in a landfill site, or incinerated. For a detailed description of the wastewater treatment process, visit the USGS Water Science for Schools web site .
Eutrophication is a form of pollution.
Eutrophication is the process of becoming better nourished either naturally or artificially. In terms of a lake, eutrophication occurs naturally with the gradual input of nutrients and sediment through erosion and precipitation resulting in a gradual aging of the lake. Humans speed up this natural process by releasing nutrients, particularly phosphorus, into rivers and lakes through municipal and industrial effluent and through increased soil erosion by poor land use practices. Eventually, a lake has high nutrient concentrations and dense growths of aquatic weeds and algae. These plants die and decompose causing depletion of dissolved oxygen in the water.