Freshwater pollution and its control Bo, Dane, Alisha, Haunz, Chelsea

Nutrient Pollution  When an excess of a nutrient enters a water system. (eutrophication) For example: when excess phosphorus enters surface waters, it fertilizes algae and aquatic plants, boosting their growth rates and populations. The growth provides oxygen and food for other organisms, but the algae covers the surface and deprives the deep water plants of sunlight.

Pathogens and Waterborne diseases  When disease causing organisms enter drinking water that is contaminated with human waste (sewage) or animal waste from feedlots.  Biological pollution causes more human health problems than any other type of water pollution.  Causes giardiasis, typhoid, or hepatitis A  Treating sewage is one way to reduce risk of pathogens and waterborne diseases.

Toxic Chemicals  When toxic organic substances enter water systems  pesticides, petroleum products, and other synthetic chemicals. Also toxic metals arsenic, lead, and mercury.  Legislating and enforcing more stringent regulations of industry can reduce releases of these toxic inorganic chemicals, also modifying our industrial processes and purchasing decisions can help us rely less on these substances.

Sediment  Sediments can impair aquatic ecosystems.  Mining, clear-cutting, land clearing, and careless cultivation of farm fields expose soil to wind and water erosion.  When a clear water river receives a heavy influx of eroded sediment, aquatic habitat can change dramatically, and fish adapted to clear-water environments may not be able to adjust.  We can reduce sediment pollution by better managing farms ad forests and avoiding large-scale disturbance of vegetation.

Thermal pollution  Water holds dissolved oxygen, and as temperature rises, its capacity to hold oxygen decreases.  Some aquatic organisms cannot survive this.  When we withdraw water from a river and use it to cool an industrial facility, we transfer heat energy from the facility to the river where the water is returned.  Also removing vegetation from streams raises surface temperatures.  To little heat can also be a problem. In dammed rivers, water at the bottom of the reservoirs is colder than surface water, when it is released from the bottom, the temperature of the water downstream drops.