Wastewater is treated using physical, chemical, and biological methods in wastewater treatment plants to prevent water contamination. Physical methods include screening and sedimentation, chemical methods use chlorine and ozone, and biological methods use bacteria. Different processes are used depending on the treatment stage.
Different wastewater treatment methods are used before wastewater disposal. The goal is to prevent water contamination in recreational areas or water supplies once treated wastewater is released. Most of the time, wastewater is treated during a continuous flow process by chemical wastewater treatment or by physical or biological methods. These methods and the different stages of treatment occur in 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 chemicals or biological materials to treat the water. Water can be screened to filter out large items. It can also be treated by sedimentation, during which solids settle to the bottom under the influence of gravity. The solids-free water can then be removed. Other physical processes include the addition of air to supply oxygen within the wastewater and the water can also be passed through a filter to remove solid materials.
Another way to treat wastewater is to use chemicals like chlorine, which kills bacteria, as well as ozone. These chemicals serve to oxidize the water, kill any pathogens, and slow the rate of decomposition. An acid or base may also be added to the mix to neutralize the pH of the wastewater, while the coagulating chemicals react with the materials in the water to make them easier to remove. Chemical and physical methods are often combined in the wastewater treatment process, for example when activated carbon is used to remove organics.
Bacteria 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 has a purpose and different processes are used depending on the treatment stage. Physical processes are often used in the pre-treatment, which involves the use of sieving, cutting and shredding devices. Primary treatment includes physical and chemical processes and depends more on large tanks. Biological wastewater treatment is typically the method used for secondary treatment, and physical or chemical methods are used in the more advanced stages of the wastewater treatment process. Wastewater is usually treated in stages that combine various physical, chemical and biological methods.
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