Chambers Creek Regional Wastewater Treatment Plant Layout | Sewer Division | Public Works and Utilities

Public Works & Utilities >> Sewer Utility >> Chambers Creek Wastewater Treatment Plant >> Plant Layout /How it Works

wastewater treatment process - click to enlarge

Wastewater treatment is a multi-stage process involving the separation of wastewater from solids. The process involves

screening
grit removal
clarification
aeration
digestion
pressing
final treatment of liquids with ultraviolet light
final treatment of solids by processing into fertilizer

Screening Perforated plate screens and step screens catch large pieces of debris and other solids as wastewater enters the treatment plant. Material trapped by the screens is disposed of in a sanitary landfill.

Grit Tanks Air diffusers are used to keep solids suspended in the wastewater allowing sand and grit to settle to the bottom. The sand and grit are removed from the tanks and taken to a sanitary landfill.

Primary Clarifiers Tanks where heavier solids are allowed to sink to the bottom while automatic skimmers remove particulate matter and grease that floats to the top. The grease is pumped to a concentrator tank to remove excess water then to the digesters for anaerobic bacteria digestion.

Aeration Basins and Secondary Clarifiers Basins that receive effluent (wastewater) from primary clarifiers where air is infused as a source of oxygen for aerobic bacteria. The bacteria consume and break down organic material and sink to the bottom. Some of the bacterial sludge and solids are sent to the centrifuges and the rest is reused in the secondary clarifiers. Fines (small particles) are also removed during secondary clarification. Liquids are sent to ultraviolet light disinfection.

Digesters Solids sent to the digesters are reduced in volume by anaerobic bacteria and heat. During the process biogas (a mixture of methane and carbon dioxide) is produced and is used as fuel for gas fired boilers and in the fertilizer manufacturing process.

Centrifuges Bacterial sludge from the digesters is dewatered by spinning in centrifuges. Liquids are sent back to the primary clarifiers and solids go to the fertilizer manufacturing facility.

Fertilizer Manufacturing Facility Dewatered solids from the centrifuges are sent to an on-site manufacturing plant where they are further processed, dried, and bagged as SoundGRO, an EPA 'Exceptional Quality ' Class A pelletized fertilizer for residential and commercial use.

Ultraviolet Light Disinfection After leaving the secondary clarifiers, wastewater receives final treatment by ultraviolet light to destroy any pathogens prior to discharge into Puget Sound.