Class AA Surface Water: MBR Treatment Plant Design and Construction Experience at Concrete, Washington

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The Town of Concrete, Washington, a rural community of about 950 persons located in the front range of the Cascade Mountains, has been in critical need of a new wastewater treatment plant to replace a lagoon treatment facility that is frequently out of the permit discharge limits for BOD5 and total suspended solids. The effluent is discharged to the Baker River which has the highest surface water quality classification (AA – extraordinary) because it is an important habitat for protected species of fish under the Endangered Species Act, including native Chinook salmon. Therefore, the Town's goals for a new treatment plant include not only the need to increase treatment capacity and comply with existing permit requirements, but to provide the highest effluent quality achievable to mitigate in-stream flows and enhance fish habitat in the Baker River.

The Town primary design criteria for the new wastewater treatment plant were to:

Meet the effluent water quality goals using MBR technology.

Expandable to accommodate the projected flow increases.

Keep the existing lagoon system in full operation during construction of the new plant.

Capability to operate successfully with the operator spending not more than a few hours each week on-site.

The plant is currently under construction with an anticipated completion time in December 2007. The plant design flows are 160,000 gpd annual average day and a maximum day flow of 320,000 gpd. The MBR system includes two parallel trains, a thickener (small membrane unit) and two aerobic digesters for waste sludge treatment; and treatment of the recovered supernatant from the thickener. Pre-treatment consists of dual 3-mm microstrainer units; a grit collector; and soda ash feed system. The disinfection system consists of two parallel UV reactor units. If needed, the plant capacity can be expanded to provide a maximum day flow of 480,000 gpd with the addition of additional membranes in the MBR basins.

The purpose of this paper is to provide and overview of the:

project design criteria development;

MBR system selection process;

Challenges during construction; and

anticipated startup and operations approach

Document Type: Research Article


Publication date: January 1, 2008

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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