Water Plant Waste Stream Characteristics

Water treatment plants do not only create clean water, but waste as well. Something must be done with the substances being removed from the water. They can be disposed of in many ways, including being discharged out into the environment.

Origins of Contaminants

• What exists in the output from the plant depends on two things: what was in the water to start with, and what treatment was used to clean the water. Chemical reactions between the two create a variety of outputs. Toxicity depends mostly on what was in the water to start with, but also how the input reacts with the filtering agents.

Waste Outputs

• If the water contained a lot of sediment, sludge may be produced in quantity. Even relatively clean water generally has some suspended particles that filtration, osmosis or distillation can concentrate. Heavy metals, herbicides and pesticides can be present. Some filtering substances attract particles in the water, and are then filtered out; these also form part of the sludge.

  Concentrated brine, where the salt in the water has become more prevalent as clean water is removed can be very toxic. Most water has salt in it at some level, and some filtering can produce salt also.

  Spent filter output, such as sand, charcoal and diatomaceous earth may contain contaminants but these are not suspended in water. However, rain and groundwater can pull contaminants out into the environment.

Disposal Methods

• The outputs can be disposed of in different ways. Liquid can be pumped out over a large surface area to slowly evaporate. Holding ponds take quantities of liquids. Landfills and incinerators are used for solid waste. Sometimes wet waste is pumped into the sanitary sewer system, to be filtered again at the sewage treatment plant.