How Does a Waste Water Treatment Plant Work?

What Does a Waste Water Treatment Plant Do?

A waste water treatment plant is designed to take all used water and waste from municipal sewage lines and run it through a cleaning process to remove harmful bacteria, chemicals, particles and other pollutants while adding oxygen to the water prior to releasing it back into the environment. The used water includes water from toilets, baths, washing machines, garbage disposals, sinks, drains, runoff and groundwater.

How Waste Water Arrives at the Treatment Plant

Waste water arrives at a treatment plant through many miles of sewage lines where initial screening is used to keep material waste such as, diapers, cloth and plastic from entering the raw waste water area. This material waste is disposed of, and the remaining waste water is pumped to a basin or holding tank. The basins typically allow small particles contained in the waste water to settle to the bottom of the basin. The particle residue is scraped from the basin, and the top of the waste water is skimmed while in the basin to remove scum or particles that float to the top.

Separating Sludge from Water

Once filtered for material waste, small particles and scum, waste water is pumped to another basin for a second step of purification. While in the second basin, waste water is infiltrated with a large amount of oxygen (an aeration process) and good bacteria that feed on any remaining harmful organic matter. The growth of helpful micro-organisms can be increased by monitoring the ratio of good bacteria, harmful bacteria and oxygen. A process of pumping into two additional "settling" basins allows for any activated sludge to be separated and returned to the aeration process.

Treating the Water

The remaining water, or effluent, is sent through several treatment processes that include a 24-hour monitoring, sampling and testing process prior to releasing effluent back into the environment.

Treating the Sludge

The initial treatment of sludge is performed through a spinning process to remove and dispose of any inorganic material. The remaining sludge is pumped into digesters that process the solid waste material through bacterial decomposition that renders a form of stabilized sludge, or bio-solid, which is EPA approved to be used on farmland as fertilizer.