How the Wastewater Treatment Process Works

August 17, 2021

Most of us don’t think about water once it goes down the drain or toilet, but comprehensive wastewater management is an important part of our society. Without it, we’d be drinking contaminated water! This post will teach you the steps wastewater companies go through to keep our water clean.

Screening and pumping

The first step in this process is screening all objects and materials like wood fragments, plastics, rags and grease from the rest of the water. These larger materials are removed from the rest of the water, washed, pressed and sent to the landfill. The remaining water is then pumped and moved along to the next stage.

Grit removal

Heavy-yet-fine materials like sand and gravel are removed from the wastewater in this step. Again, these fine materials are disposed of in the landfill.

Primary settling

Some material will inevitably make it through step two, but it’ll be removed in this phase. During this step, the leftover material—called primary sludge—settles in large circular tanks called clarifiers. The sludge is pumped out of the bottom while the wastewater exits from the top of the tank. Wastewater companies will also skim floating debris off the top of the water and treat it with chemicals in this step.


Wastewater receives most of its treatment during aeration via biological degradation. In this step, microorganisms consume the pollutants and transform them into cell tissue, water and nitrogen. This process is similar to what occurs naturally in lakes and ponds. However, it only takes a few days, as opposed to a few years.

Secondary settling

The water is then moved into large tanks once again, which are called secondary clarifiers. These tanks allow the treated wastewater to separate from the sludge created in the previous step. The sludge yielded during secondary settling is returned to the aeration tanks for further treatment.


Water is approximately 90 percent treated after coming out of the secondary clarifiers, but once it’s out, it’s polished by filtering through 10-micron polyester media. Any materials captured in the filters are backwashed and returned to the start of the treatment plant.


You’d think the water would be safe to consume at this point. However, wastewater facilities take extra care to disinfect it one more time. Most treatment plants use ultraviolet lights to disinfect the water without the need for any more chemicals. This advanced process ensures bacteria and pollutant levels are within a safe range for consumption and reintroduction to the environment.

Effluent disposal

After the water has been tested and meets stringent requirements set by the Department of Natural Resources, it can be reintroduced to the environment. Treatment facilities that do not meet the DNR’s requirements are subject to hefty fines.

Call our team today!

If you have further questions about the wastewater treatment process or need to upgrade or replace your current system, call our team at Enviro-Line Co., Inc. With a variety of wastewater treatment services and competitive rates, we’re proud to provide quality services that meet the highest standards.

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