What is the wastewater treatment process?

So, the question you all seem to be asking, what is the wastewater treatment process?

Wastewater treatment is one of our key offerings where we offer a solutions-based approach to treating effluent prior to discharge; from process design, plant and chemical programmes, to sludge management and water reuse.

If trade effluent is to be introduced directly into surface waters (rivers, streams, sea), a consent to discharge is generally required. Effluent discharged directly to sewers must also be kept within set parameters. This is why wastewater treatment is so important, it reduces the risk of financial penalties, plant closure or water pollution.

So, what is the wastewater treatment process then?

Generally, it can be split into two areas; primary and secondary wastewater treatment.

Primary Wastewater Treatment

The first step of the process starts with the wastewater or effluent entering the system where it goes through screens to remove any large solids. This step prevents any blockages in the system further along.

The wastewater then travels through to the primary clarifier tank where the water if left to settle, and gravity takes place, allowing any remaining solids to sink to the bottom. This process is helped through the addition of coagulants and polymers. If the solids are light or contain oils and greases, they typically won’t settle and so they are removed by dissolved air flotation (DAF) These solids settle to form sludge (or float in the case of a DAF process) which can be a pain for any wastewater treatment plant. Our article on the removal of sludge provides cost-effective solutions to wastewater treatment plants.

This is the final stage of primary wastewater treatment.

Secondary Wastewater Treatment

The secondary wastewater treatment phase starts with the primary effluent flowing from the primary clarifier or DAF into the aeration tank. Air is pumped into the aeration tank, promoting microbial growth in the wastewater. The microbes feed on organic material, forming flocs and are referred to as the mixed liquor suspended solids (MLSS).

In a conventional wastewater treatment plant, the effluent then travels from the aeration tank to the secondary clarifier where the flocs are allowed to settle and sink to the bottom of the tank. Membrane bioreactors (MBRs) are becoming more popular to retrofit to conventional activated sludge plants and are used extensively in new builds, with the main advantages of being able to remove the final settlement phase, hold more MLSS and therefore reduce the footprint of the entire process. It is here where the flocs are removed and travel to the sludge treatment plant.

The wastewater journey is almost complete. After leaving the secondary clarifier, the water is disinfected where it can be reused back into the industrial process or can be discharged via sewer or water course.

And there you have it, the wastewater treatment process. A lot of work goes into keeping our waters safe and in the process discussed above, a lot our chemicals and expertise are used to keep wastewater treatment plants running smoothly.

If you have any queries about this article, don’t fail to get in touch with us.