Sewage Treatment: How Does It Work?
Monday, April 19, 2021

The United States processes about 34 billion gallons of wastewater each day.

Sewage treatment facilities are some of the most expensive items municipalities have to manage, but they are also some of the most complex. Their cost to taxpayers is usually only marginally behind schools and emergency services.

Although wastewater treatment is a quintessential government function, politicians rarely campaign on it.

Still, water treatment is the backbone of cities and counties. Understanding how these complex facilities work is important for every community member.

In the following article, we'll explain how sewage treatment works and why it matters. Keep reading to learn more.

What Is Wastewater?

Municipalities collect sewage through pipes and gather it at a central treatment facility. For good or bad, we build many of these facilities near or around freshwater. This is necessary for release and discharge after treatment.

Sadly, the proximity near water has caused unexpected spillage and pollution after heavy rains or flooding. These issues are often a problem with changing water levels near or around the plant.

The wastewater itself consists of sewage, rain runoff, and industrial discharge. This liquid is high in phosphorus and nitrogen from human waste. It also contains food, soaps, detergents, and other chemicals.


The first step in wastewater treatment is filtering. Sand, debris, and other solids like grease, metals, tampons, and fats all need removal. You perform this pre-treatment through a series of ever-finer filters.

Once you screen these solids, workers take the waste to a landfill for disposal.

Primary Sewage Treatment

The first full stage of water treatment consists of a settling process. In massive tanks, the wastewater is allowed to sit.

Heavier materials like sludge then settle to the bottom while greases and other chemicals rise to the top. Entech Design's EchoSmart sludge level monitors are used at this stage to monitor effluent.

You then drain off the bottom sludge once gathered and skim the top oils and chemicals.

Secondary Treatment

Next, you subject the wastewater to biological agents like bacteria and protozoa. These creatures "eat" any biodegradable elements in the liquid.

This material is foodstuff remnants, skin cells, animal material, and some soaps. It's a little-known fact that a large part of sewage treatment is done through these natural processes.

Tertiary Treatment

This last step uses disinfectants like chlorine and ultraviolet light. These methods kill off the most resilient bacteria and viral agents.

Ultraviolet light is considered healthier for the environment than some chemical disinfectants. In some cases, chlorination techniques have left carcinogens in the treated water. We rectify this through the extra step of dechlorination.

However, the use of ultraviolet light is sometimes less effective in cloudy water. These sedimentary particles act as light shields for the bacteria.

Finally, the water is released back into the environment. This is usually a river, wetland, or outlet pound.

The Backbone of Society

Our shared biology makes sewage treatment a necessity of modern living. As the above article states, it's a sometimes natural process that requires complex coordination.

And much of your taxpayer dollars go to funding these efforts. This money ensures our plumbing works effectively and the environment remains pristine.

Want to learn more about Entech Design's sewer and wastewater treatment technology? Contact us today to speak with a representative.