The Resulting Clean Water Can then be Recycled and Returned to The Environment

Water and wastewater treatment plants map are essentially the same thing, except that wastewater is water that has been used in homes or businesses. Wastewater contains everything that is flushed down toilets, washed into drains and down street gutters, as well as rainwater runoff. All this wastewater is carried to sewage treatment plants to be processed.

This water is often reused for things like irrigation, manufacturing, cooling and fire fighting. Clean water is essential for life, and the ability to supply it and treat wastewater are regarded as National Critical Functions – functions that, if disrupted, would debilitate the U.S. economy, threaten national security or endanger public health and safety.

In addition to removing organic materials, such as sand, grit and grease, many wastewater treatment processes also remove chemicals that are toxic to the environment or human health. This includes disinfectants (such as chlorine and chlorine dioxide) and other chemical reagents that are used in industrial processes such as battery manufacturing, electric power generation, iron and steel production, petroleum refining and petrochemical processing, food industry, paper and textile mills and wood preserving.

The first step of treatment for both drinking water and sewage is mechanical separation. This involves separating the water into greywater and blackwater, which is then treated differently. Greywater is wastewater generated from washing laundry and dishes, bathing and showering that can be reused, whereas blackwater is human waste and cannot be reused.

Once the heavy solids are removed, the contaminated wastewater is treated using large circular tanks called clarifiers. The wastewater is agitated in the tank to help it settle so that the heaviest material will sink to the bottom and the lighter sludge can float to the top. The liquid exits the top of the tank, and the settled sludge is sent to digesters to be broken down by bacteria. Chemicals are added to the digesters to help remove phosphorus, which can cause excessive algae blooms and waste plant growth in lakes, rivers, estuaries and oceans.

Some nutrient-rich wastewater, such as that from pharmaceuticals and some agricultural industries, is treated by a process called enhanced biological phosphorus removal. This uses special bacteria that eat phosphates, which can be used as fertilizers. This process helps to restore the balance of phosphorous and nitrogen in the aquatic ecosystems.

Other types of wastewater are treated by other methods, such as sand filtration and aeration. These techniques can be very expensive, so they are typically only used for the most contaminated wastewater.

The final stage of wastewater treatment is disinfection, which usually involves adding chlorine or bleach to kill any remaining microorganisms in the water. It is also important to control the amount of chlorine that is added to the water, as too much can damage water treatment plants and make the water toxic to humans and animals.