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Sewage Treatment System
Last update date October 4, 2023
Sewage discharged from homes and factories is transported to a water reclamation center through sewer pipes. The large amount of sewage is treated by a combination of physical, biological, and chemical treatment at a water reclamation center.
Sediment basin (physical treatment)
In the sedimentation basin, large debris and stones are precipitated and removed.
Garbage is collected by a dust remover, and the water is pumped up and sent to sedimentation pond first.
In the sand basin, water flows slowly and removes large debris.
A coarse screen is installed to remove large pieces of wood.
First sedimentation pond (physical processing)
At first it takes more time in sedimentation pond, and the sand basin precipitates small debris that had not settled down. These are removed as sludge (settled garbage) and sent to the sludge recycling center for processing.
Sludge is collected by a stirring machine.
It's the entrance to sedimentation pond. The water is flowing slowly.
Oil and other debris floating on the surface, such as oil, is also removed by a removal device.
Reaction tank (biological treatment)
The reaction tank is the heart of sewage treatment. By sending a large amount of air, microorganisms decompose dirt dissolved in water. Microorganisms that have increased after decomposing dirt form a lump called floc. Flocs look like mud, so it is called activated sludge.
Click here if you want to know more about microorganisms in activated sludge.
Treatment of sewage by microorganisms
Fine air bubbles are sent from the airborne device.
Sewage and activated sludge are mixed in the reaction tank. White foam is air.
It is a reaction tank that does not contain water. Air comes out of the blue disk lined up at the bottom.
Final sedimentation pond (physical processing)
In the final sedimentation pond, activated sludge is slowly precipitated over time. This supernatant is called treated water. Part of the sedimented sludge is returned to the reaction tank again, and the rest is sent to the sludge adjustment tank for treatment.
The precipitated activated sludge is collected by a stirring machine and sent to the reaction tank by a return sludge pump.
The supernatant sludge sinks is transparent.
Processed water flows out of the overflows on the surface of the pond.
Contact tank (chemical treatment)
In the contact tank, the treated water is disinfected with sodium hypochlorite. Then it is released into rivers and seas.
Disinfection chemicals near the entrance.
Water after chemical injection flows into the contact tank.
The contact tank is like a waterway and is disinfected while it flows slowly.
Sludge adjustment tank (physical treatment)
In the sludge adjustment tank, sludge sent from the first sedimentation pond, reaction tank and final sedimentation pond is deposited and concentrated. The concentrated sludge is sent to the sludge recycling center where it is processed.
For inquiries to this page
Sewerage River Bureau Sewerage Facilities Department Water Quality Section
Phone: 045-621-4343
Phone: 045-621-4343
Fax: 045-621-4256
Email address: gk-suishitsu@city.yokohama.lg.jp
Page ID: 132-154-875
