How Does A Sewage Treatment Works Operate? Key Stages You Should Know
How does a sewage treatment plant work? In this article, we will look at the purpose and function of a sewage treatment plant, explaining the key processes involved and how proactive sewage treatment plant management can reduce the risk of pollution and ensure a more efficient and safer wastewater management process.
So, how does a sewage treatment plant work?
1. Preliminary/Primary Treatment
As the first stage of sewage treatment, raw untreated sewage is screened to remove large particles and debris so that they don’t clog pipes and equipment or hinder further treatment stages downstream. Slurry is filtered and corralled to remove sticks, plastics, rags, and other large objects, and then is passed through primary filters to remove sand, grits, gravel and other heavy particles. This stage also involves regulating the flow of wastewater to improve efficiency and consistency of treatment throughout the plant.
2. Secondary Treatment
Next, the sewage is processed for secondary treatment, which involves various biological processes to break down organic matter and nutrients. In some processes, bacteria or microorganisms are introduced to consume organic pollutants and convert them into less harmful substances – such as carbon dioxide, water, and biomass.
This is known as the activated sludge process, and takes part in an aeration tank, in which the wastewater is mixed with air and a biological sludge containing the appropriate microorganisms. The wastewater is then channeled into a settling tank in which the treated water is separated from the solid sludge residue. Some of this sludge can then be recycled back into the aeration tank to maintain a healthy population of microorganisms, while the excess is often removed for further processing or disposal. Treated sludge can often be safely repurposed as agricultural fertiliser or even biomass fuel.
3. Tertiary Treatment
The third and final stage of sewage treatment includes a range of purification treatments to remove any remaining contaminants. These include agricultural nutrients such as nitrogen and phosphorus, as well as small-scale pathogens and microscopic particles. This can include several stages of filtration, disinfection, UV treatment, and chemical treatment in order for the process water to fully meet the required environmental or legislative standards for reuse, or discharge into the public sewer. Common wastewater treatment methods include sand or membrane filtration, ultraviolet (UV) disinfection, and treatment with chlorine or other chemicals. Commonly, after this stage, the treated wastewater also known as final effluent is discharged into an adjacent water course such as a river, stream or the sea. Final effluent is monitored for quality and suspended solids and must meet the minimum standards set by the governing authorities
Environmental Considerations Of Sewage Treatment Plant Pollution
In an efficient wastewater process, the risk of environmental pollution is low, as pollutants are progressively removed at each of the three stages of treatment, and the discharge is tested for safety before being reused or disposed of.
However, there are nevertheless various environmental risks associated with sewage treatment, including:
Greenhouse gas emissions from the byproducts of wastewater treatment at the primary and secondary stages including nitrous oxide and methane.
Accidental discharge of improperly treated effluent into public waterways, usually arising from a flooded or overloaded system. This can harm aquatic ecosystems by introducing toxic compounds into the water or by stimulating an algal bloom from an influx of nutrients.
Incorrect sludge disposal can contaminate local soil or water sources.
The sewage treatment process itself can be energy intensive, leading to a high carbon footprint for wastewater treatment plants.
The Benefits Of Professional Sewage Treatment Plant Installation And Maintenance
Many of these environmental risks can be mitigated or avoided through professional plant design and installation, and a proactive approach to ongoing maintenance. For example, careful capacity planning at the design stage can size the plant to prevent overloading, which is a common cause of accidental effluent discharge and pollution. At the same time, an experienced contractor could work with you to devise the most efficient treatment process for your application, incorporating the most efficient processes to maximise pollutant removal while minimising energy expenditure.
Find Out More
As local authority pumping systems specialists, our engineers can help optimise the performance of your sewage treatment plant and minimise the risk of pollution. Get in touch with Samatrix today to discover the benefits of our progressive and sustainable pumping solutions for sewage treatment plants.
