What Is Wastewater Treatment? Purpose Of Wastewater Treatment
What Is Wastewater Treatment?
Wastewater treatment is a crucial process that is used to remove contaminants from wastewater and convert it into a form that can be returned to the environment without causing harm. This process is carried out in a wastewater treatment plant which can take many forms depending on the type of wastewater being treated.
For example, sewage treatment plants are used to treat domestic wastewater while industrial wastewater is often treated in a separate industrial wastewater treatment plant or in a sewage treatment plant after pre-treatment.
Other types of wastewater treatment plants include agricultural wastewater treatment plants and leachate treatment plants.
The treatment process typically involves a combination of physical, biological, and chemical processes, such as sedimentation, oxidation, and polishing. These processes work to remove pollutants and harmful substances from the wastewater making it safe to return to the environment or to reuse.
One of the main by-products of wastewater treatment is sludge, which is often treated in another wastewater treatment plant. Biogas can also be produced as a by-product if anaerobic treatment processes are used.
The main goal of wastewater treatment is to make the wastewater safe for disposal or reuse. However, before treatment begins, it is important to consider the options for disposal or reuse so that the appropriate treatment process can be used.
This is particularly important when dealing with industrial wastewater, which may contain specific pollutants that require specialized treatment. Overall, wastewater treatment is an essential process that helps to protect the environment and promote sustainable water management.
Purpose Of Wastewater Treatment
Wastewater treatment is the process of removing contaminants from used water before it is released back into the environment. If not properly treated, wastewater can harm fish and wildlife populations, deplete oxygen levels, and lead to beach closures and other restrictions on recreational water use.
The goal of wastewater treatment is to remove as much suspended solids as possible before the effluent is discharged back to the environment.
How Is Wastewater Formed?
Wastewater is formed by a variety of activities such as bathing, washing, using the toilet, and rainwater runoff. It is essentially used water that has been affected by domestic, industrial and commercial use. Some wastewaters are more difficult to treat than others, such as industrial wastewater which can have a high strength nature, while domestic wastewater is relatively easy to treat.
Wastewater can cause pollution problems in a variety of ways, not just when it is not treated properly, but also when it is not collected and treated at all. Many older cities have combined sewer systems that collect domestic sewage in the same pipes as storm water runoff.
When heavy precipitation occurs, the system can’t hold all the water and a mixture of raw sewage and storm water is released directly into the environment, otherwise known as a combined sewer overflow (CSO).
Process Of Wastewater Treatment
The process of wastewater treatment is typically divided into two main stages: primary and secondary treatment. In the primary stage, solids are allowed to settle and be removed from the wastewater. The secondary stage uses biological processes to further purify the wastewater.
Sometimes these stages are combined and in some cases additional treatment such as tertiary treatment and advanced wastewater treatment are used to achieve a higher level of purification.
Types Of Wastewater Treatment Plants
Wastewater treatment plants are used to remove contaminants from wastewater and produce an effluent that is suitable for discharge into the environment or for reuse. There are several types of wastewater treatment plants, including sewage treatment plants, industrial wastewater treatment plants, agricultural wastewater treatment plants, and leachate treatment plants.
Sewage treatment plants are used to treat wastewater from households and businesses, and may also include pre-treated industrial wastewater. There are many different sewage treatment processes to choose from, including decentralized systems and large centralized systems.
Sewage treatment often involves two main stages: primary treatment, which removes large solids and floating materials, and secondary treatment, which reduces organic matter using aerobic or anaerobic biological processes.
Advanced treatment may also include a tertiary treatment stage with polishing processes and nutrient removal. Engineers and decision makers must take into account technical, economic, and sustainability criteria when choosing a suitable technology.
Industrial wastewater treatment plants are used to treat wastewater produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment.
Most industrial processes have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with regulations regarding disposal into sewers or into rivers, lakes or oceans.
Treatment processes may include brine treatment, solids removal, oils and grease removal, removal of biodegradable organics, removal of other organics, removal of acids and alkalis, and removal of toxic materials.
Agricultural wastewater treatment plants are used to control pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water.
Agricultural wastewater treatment is required for continuous confined animal operations like milk and egg production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater. Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles. Animal slurries are usually treated by containment in anaerobic lagoons before disposal by irrigation or land application.
Leachate treatment plants are used to treat leachate, which is a liquid that has percolated through or drained from solid waste and has picked up contaminants. Leachate treatment plants use a combination of physical, chemical, and biological processes to remove pollutants from the leachate. The treatment processes used will depend on the type and level of contaminants present in the leachate.
Overall, the global sewage treatment rate is around 52%. However, there is a significant disparity in sewage treatment rates between high-income countries, which treat approximately 74% of their sewage, and developing countries, which treat an average of just 4.2%.