Water pollution

"Man is a complex being; he makes the deserts bloom and lakes die."
— Gil Stern
Pesticides are carried in rainwater from farm fields, suburban lawns, or roadside embankments into creeks.
Results:
affect and damage the nervous system;
cause liver damage;
damage DNA and cause a variety of cancers;
cause reproductive and endocrine damage;
cause other acutely toxic or chronic effects.

"Society, my dear, is like salt water, good to swim in but hard to swallow."
— Arthur Stringer, author, The Silver Poppy
Mercury comes through air pollution from industrial plants. In the water, the elemental mercury is converted to methylmercury by certain bacteria, after which it moves into food through a fish.
Young children and fetuses (плод) are most at risk because their systems are still developing.
Mercury causes neurological problems, including slower reflexes, learning deficits, delayed or incomplete mental development, autism, and brain damage.
Mercury for adults is also a problem, causing:
central nervous system effects like Parkinson's disease, multiple sclerosis, and Alzheimer's disease (разновидность пресенильного слабоумия);
heart disease;
death or irreversibly damaging areas of the brain.

PCBs, Dioxins, and Other POPs
PCBs polychlorinated biphenyl - ПХД полихлорированные дифенилы
dioxins - poisonous chemical by-products of the manufacture of certain herbicides and bactericides
POP - persistent organic pollutants tend to collect in the fatty issues of animals.

Control of water pollution
In urban areas, domestic sewage is typically treated by centralized sewage treatment plants. Plants are designed to control conventional pollutants(обычные загрязнит. в-ва) Well-designed systems can remove 90% or more of these pollutants.

Industrial Wastewater Treatment
Some of these facilities remove the toxic components, and then send the partially-treated wastewater to the municipal system.
Dissolved air flotation system for treating industrial wastewater.

Agricultural Wastewater Treatment
Sediment (loose soil) washed off fields is the largest source of agricultural pollution
Nutrients are typically applied to farmland as commercial fertilizer, materials left after the crop has been harvested, water irrigation, wildlife

Urban runoff (stormwater-ливневая вода)
Effective control of urban runoff involves reducing flow of stormwater, as well as reducing pollutant discharges. Local governments use techniques (BMPs-best management practices) to reduce the effects of urban runoff : filters, clarifiers, biological reactors