Inwood Wastewater Treatment Plant  Upgrade

     In response to increased demand on the treatment facility, the District is planning to upgrade capacity at the      wastewater treatment plant.  The Inwood Wastewater Treatment Plant is rapidly approaching 90% of its design capacity.  The WWTP serves areas where heavy housing development is underway.  With the heavy growth planned within the service area, the District is acting now to prevent shortages of treatment capacity in the near future.  Construction is planned to begin Fall/Winter 2006 with a one-year construction period.  The upgraded plant is planned to begin operation by Winter 2007. 

 

Treatment Process

An SBR system receives the raw wastewater directly into the treatment basins similar to other aerobic extended aeration processes except that the flow is not a continuous flow through, but is handled in a batch process typically cycled between multiple basins.  One basin will fill with influent wastewater, a separate basin will aerate accumulated sewage for biological treatment.  Following the aeration cycle, the aerated basin is then allowed to settle for predetermined period of time and then clear water is decanted from the top level of water within the basin.  BOD removal, nitrification, denitrification, and solids reduction are all accomplished within a single treatment unit.  This eliminates the need for a separate clarifier, sludge return equipment and scum removal devices resulting in a more compact unit size and reduced energy requirements.  The SBR process is also able to handle variations in inflow rates due to the batch sequence allowing diversion of flows between basins without increase in flow through velocities, which would result in carryover of solids. 

 Primary treatment will consist of mechanical fine screening and grit removal units.  Secondary or biological treatment will occur in the SBR unit as previously described.  The waste stream will then be processed through an ultraviolet light disinfection system, followed by mechanical post aeration prior to effluent discharge into the receiving stream.  The solids wasted from the SBR process will be digested in an aerated sludge digestion tank with solids dewatered through a belt filter press.  The sludge cake is then hauled to a landfill for disposal or land applied. 

 

Plant Details

The Inwood Wastewater Treatment Plant was completed in April of 2001 and has been operated by the District in accordance with its permit.  The Inwood Wastewater Treatment Plant will have its capacity increased to 2.25 MGD in two phases.  The first phase of the project will increase the plant capacity from .75 MGD to 1.5 MGD.

 

Phase I will include: 

• An additional screw pump will be added to feed the plant.
• Additional pretreatment works will be installed boosting the pretreatment capacity for 2.25 MGD normal flow with a peak flow of 6.75 MGD.

• Four new SBR treatment basins and one new digester basin will be installed.  Two of the SBR basins will be left unequipped until the Phase II upgrade is needed.

• A new blower building will be constructed.

• The plant controls and SCADA system will be upgraded.

• The disinfection system will be expanded using an ultraviolet system.
• Allowances will be made during the design process for the potential of addition of chemical addition and effluent filtration for compliance with proposed Chesapeake Bay requirements.

 

The second phase of the project will increase the plant capacity from 1.5 MGD to 2.25 MGD and will include: 

• Equipment for the extra basins provide in Phase I.

The total estimated cost for the Phase I construction is $8,262,899.

 

To see the Inwood Wastewater Treatment Plant site plans click here.

To view images of the Inwood Wastewater Treatment Plant site during construction click on the images below.