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Pollutants in rivers and streams
-Dirt is a big cause of pollution in our rivers and streams. Rain washes dirt into streams and rivers. Dirt can smother fish and other animals that live in the water. If plants can't get enough sunlight because the water is murky, they die.
-Bacteria are also a big water quality problem. Not all bacteria are harmful, but germs and viruses that can make you sick might be in the water. Bacteria can come from combined sewers after rainstorms and runoff of animal waste from farms, pets, and wildlife.
-Nutrients are element needed for animal or plants to grow. The two most common nutrients found in water are nitrogen and phosphorus. They cause algae to grow and can turn the water green.
The major sources of nutrients are runoff of fertilizers from farms and lawns, animal waste, sewage treatment plants, and septic systems.
Farmers, homeowners, cities, and towns are all working to reduce the amount of nutrients that get into rivers and streams.
Water treatments for domestic use
Filtration: removes suspended matter from water by mechanical "screening"
Oxidation: used primarily for disinfection. It is probably the most popular oxidizing technique that changes taste- and odor-causing substances into innocuous forms.
Ion-exchange: employs a tank containing a bed of insoluble material. This material (a resin) has a negative charge with positively charged sodium ions attached to it.
Ultraviolet irradiation: Ultraviolet light provides bacterial killing action much the same way sunlight helps kill bacteria.
Aeration: This process treats water through intimate contact with air.
Ph neutralization: In order to increase the overall efficiency of a water conditioning system, acidic water may be pre-treated by passing it through a tank containing a bed of granular lime, calcium carbonate or marble before entering the remainder of the treatment process. Similarly, alkaline water may be treated with an acid drip or injection process to neutralize the water.