What Are the 3 Stages of Sewage Treatment?

Our ability to provide fresh and reusable water depends on the systems we use to treat sewage. It allows people around the world to save time and money on resources, as well as avoid health hazards that come with consuming contaminated water. Proper sewage treatment also helps us improve our impact on the environment.

In order for sewage in water to be handled properly, several stages need to be followed in a specific order. Each step has its own parts, and this allows organizations to remove as much harmful material as possible. This guide provides the three stages involved in sewage treatment.


The sewer is often the home of large objects that are not disposed of properly, and treatment first focuses on getting them out of wastewater. This process is known as screening and involves equipment such as wood fragments, cotton swabs, wipes, diapers, facial wipes, and sanitary items that are meant for garbage bags. Screening is also done for rags, plastics, bottles, bottle caps, and other harder material that can block or damage equipment meant for handling softer objects. Less solid material, such as sand and gravel, are also focused on in this step, as heavy amounts can cause similar damage.

Organizations such as Sewer Solutions use special equipment that can handle grit and larger objects. Since softer material doesn’t cause cracks, leaks, and other forms of damage that hard objects disposed in the sewer are capable of, the equipment used in this process handles the material so that its presence doesn’t give the water any more problems. The material is washed and pressed before being placed into a landfill, which takes both hard material as well as grit like gravel and sand. Whatever equipment you use in this step, be sure it is strong enough to carry the largest of the material we mentioned.


The next step for sewage treatment centers on human waste and taking it out of the wastewater. In this process, the first half is known as primary settling, where the wastewater is put in large settlement tanks in which the organic solid matter—also known as primary sludge— sinks to the bottom of the tanks before being scraped off by large scrapers to the center of the tanks. Once the sludge shifts to the middle, it is pumped to the top where it exits the tanks. This allows for equipment to remove grease and other debris floating in the water and move it to digesters. Phosphorus can also cause problems, but chemicals are used to get it out of the water.

Next comes secondary settling, which is done after aeration, a process that uses microorganisms to consume pollutants and turn them into water, cell tissue, and nitrogen. This part involves circular tanks, also known as secondary clarifiers, which are responsible for separating the biology, or activated sludge, from the wastewater. The tanks pump air into the water so that the bacteria can easily break down the sludge that wasn’t scraped and return it to the aeration tanks. Filtration is then able to take captured material and send it to the head of the plant so that it can be treated.

Sludge treatment

The final task of this process also involves the use of tanks, with this type known as a settlement tank. This sludge treatment step focuses on keeping the volume of the water at a balanced level and the final form of it in prime shape. For things to work out, more sludge forms at the bottom of the tank as a result of the bacteria previously settling. Scraping returns to take care of anything that is left over from the previous attempts. As like with any process, it is possible for targeted material to be looked over.

The scraping takes places until the water is just about, if not completely, free of any substances that can cause harm to anyone who consumes it. The clean water then flows over a wall so that it can be filtered through a bed of sand where any additional material can be removed. The end product can then be used for a variety of purposes that allow people to save money on the sewage treatment process, such as bioplastic and agricultural grade fertilizer. The energy produced from this process can also be fed into the municipal grid and help with the plant’s overall operation.

Remember these stages so that you can properly treat sewage and provide clean water.

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