Various wastewater treatment process methods are used before wastewater is disposed of. The goal is to prevent the contamination of any water in recreational areas or in water supplies once the treated wastewater is released. Most of the time, wastewater is treated during a continuous flow process either by chemical wastewater treatment or by physical or biological methods. These methods and the different stages of treatment occur at wastewater treatment plants, facilities designed to handle large volumes of water and dispose of waste compounds safely.
A physical wastewater treatment process does not add any chemical components or biological material to treat water. The water can be screened to filter out large objects. It can also be treated by means of sedimentation, during which solids settle to the bottom under the influence of gravity. Water that is free of solids can then be removed. Other physical processes include the addition of air to provide oxygen within the wastewater, and the water can also be passed through a filter to get rid of solid materials.
Another way to treat wastewater is to use chemicals such as chlorine, which kills bacteria, as well as ozone. These chemicals serve to oxidize the water, kill any pathogens, and slow the pace of decomposition. An acid or base can also be added to the mixture to neutralize the pH of the wastewater, while coagulating chemicals react with materials in the water to make them easier to remove. Chemical and physical methods are often combined in the wastewater treatment process, such as when activated carbon is used to remove organic substances.
Bacterial and other microorganisms can be used in biological wastewater treatment. These decompose other biological materials in the wastewater and, depending on the oxygen level in the water, aerobic or anaerobic wastewater treatment methods can be performed. Organic and inorganic solids can also be removed as wastewater treatment sludge.
Each wastewater treatment process serves a purpose, and different processes are used depending on the stage of treatment. Physical processes are often used in preliminary treatment, which involves the use of screening, cutting, and shredding devices. Primary treatment includes physical and chemical processes, and depends more heavily on large tanks. Biological wastewater treatment is typically the method utilized for secondary treatment, and physical methods or chemicals are used in more advanced stages of the wastewater treatment process. Wastewater is usually treated in multiple stages that combine various physical, chemical, and biological methods.