Washington WWTP

City of Washington, NC

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With a goal to construct a new 2.1 million gallons per day (MGD) wastewater treatment facility ensuring compliance with permitted effluent limitations, develop innovative technology to dispose of sludge by land application, and to accommodate the City’s growth projections, Rivers was engaged for project planning, financial planning assistance, design, permitting, construction administration and construction inspection services.

The new wastewater treatment facilities included headworks, preliminary treatment units, secondary and tertiary treatment units in addition to sludge treatment facilities.  A draft tube aeration system was employed for introduction of oxygen into the secondary treatment process.  An aerobic digester and four sludge holding lagoons with associated sludge transfer, sludge loading and supernatant pumps were implemented for treatment of bio-solids prior to land application disposal.  The design qualified for supplemental innovative and alternative technology funding by EPA.

Rivers was later engaged once again for project planning, financial planning assistance, design, permitting, construction administration and construction inspection services associated with improvements to adequately manage periodic peak flows that overloaded existing clarifiers and tertiary filters.  This project increased the wastewater treatment capacity to 3.65 MGD and included a 95-feet diameter clarifier, two additional tertiary filters, a 2,000 SF maintenance facility, and a wastewater reuse system.

Later, Rivers was again engaged for project planning, financial planning assistance, design, permitting, construction administration and construction inspection services associated with improvements providing a redundant treatment train to the existing oxidation ditch in order continue compliance with permitted NPDES effluent requirements should the existing treatment units need to be removed from services for required maintenance and to reduce hydraulic restrictions through the plant.  New improvements included a 2.1 MGD parallel secondary treatment aeration basin, a RAS Pump Station, and an associated power zone center, as well as SCADA system for the installed equipment.  Although the new treatment facilities did not increase the overall wastewater treatment plant capacity, this phase of construction was an integral part of future phases of construction required for increases in treatment capacity.