How It Works: Urban Sewage Systems and Infrastructure

Do you know how urban sewage systems work?

Sewage systems collect sewage from communities to remove the contaminants in the water. There are 3 types of sewer systems: combined, sanitary, and storm sewers. Buildings use the sanitary system the most and consist of manholes, pipes, and pumps.

Want to get a better understanding of the sewage systems in your area?

Continue reading to discover the components of the system in every treatment. Read on to discover how the components of the system work together.

Primary Treatment

The primary treatment in sewage systems covers many processes. It includes screening, grit removal, and sedimentation.

Screening is filtering large urban waste from entering the sewer systems. It prevents the treatment plant from clogging and damaging. They put a bar screen at the entrance of the water source.

The bar screen traps the litter as the water passes through it. It requires frequent cleaning to maintain consistent water flow.

The water then flows to the grit chamber after the screening. A grit chamber is either a circular or long narrow tank. It slows down the flow of the water to remove grits like sand, ashes, and more.

Sedimentation is the process of removing suspended solids in the water through separation. Suspended solids are the remaining and floating solid particles in the water.

The water then goes through a primary clarifier. The water stays in the tank for a few hours and lets the solids settle at the bottom, in the sludge zone. The hopper collects the sludge to pump it out of the system.

Secondary Treatment

There are two methods used for this treatment: Trickling filter and activated sludge. These let the bacteria feed on the nutrients and organic materials found in the water.

The trickling filter is a circular tank filled with bedrock. The water flows into the tank with rocks. The microorganisms will begin to stick to the rock and multiply.

As mentioned, the bacteria eat the contaminants. It lowers the amount of biological oxygen demand. The BOD is the amount of oxygen needed to remove the organic matter.

You use a second clarifier to remove the microbes washed away from the rocks.

Activated sludge is the process of pumping oxygen to the aeration tank. Same with the trickling filter, it eats the organic matter. Then, it decreases the amount of BOD.

Tertiary Treatment

The tertiary treatment is the last procedure before the distribution. It’s the process of eliminating inorganic compounds like nitrogen and phosphorus.

The water goes to the flash mixer. You use the flash mixer to spread the coagulants in the water. It allows flocs to form that you can collect after some time.

Sand filters trap the floc and remove the remaining contaminants in the water. You backwash the filters to clean out the accumulated floc.

The clean water goes to the chlorine contact tank. It disinfects the water, eliminating the microorganisms. The water then flows to the discharge tank.

Precast manholes are essential in sewage systems. It’s good ventilation for the system, and it joins sewers. Besides, it allows people to make inspections and clean the urban waste systems.

Quick Guide to Understanding Urban Sewage Systems

Have you ever wondered how sewage systems work? We hope this guide helped you get a better understanding of your local sewage systems. If you encounter waste disposal problems, come back to this guide to see where things may have gone wrong.