The existing Cape Charles Wastewater Treatment Plant (WWTP) has a permitted design flow of 0.25 million gallons per day (MGD) and achieves secondary treatment using a contact stabilization package plant followed by an effluent polishing pond and ultraviolet disinfection. Waste sludge is sent to drying beds and dewatered solids are sent to a landfill for disposal.
The Town intends to install nutrient reduction technology (NRT) for nitrogen and phosphorus removal in a new 0.25 MGD facility. A Preliminary Engineering Report (PER) for the project, dated 6/17/08, was followed by a 3/9/09 Addendum that revised the scope of work to delete an expansion to 0.5 MGD, and just maintain the existing design flow. Additional materials submitted to DEQ included several Technical Memoranda and other documents covering peak flow conditions, solids generation, and results of a Value Engineering Analysis. The PER evaluated four nutrient removal options, and based on the factors of reliability, constructability, operational impact, and capital and annual cost comparisons, the selected alternative for the new NRT facility is a membrane bioreactor system operated as a 4-stage Bardenpho process. Processes being installed, and their grant eligibility as NRT, are described as follows.
Preliminary Treatment (not grant eligible): Headworks, Emergency Overflow Tank and Pumping.
Biological Treatment (grant eligible) and Solids Separation Processes (partially grant eligible):
- Fine Screens.
- Two Bioreactors, with zones dedicated to pre-anoxic, aerobic, and post-anoxic treatment. Integral mixed liquor and nitrate recycles are also provided.
- Two Membrane Tanks with support equipment housed in a Process Building; each train containing three membrane cassettes for a total of six cassettes. The membranes eliminate the need for secondary clarifiers and effluent filters.
Chemical Addition (grant eligible):
Supplemental Carbon Feed System for denitrification; designed to accommodate
Solids Processing (partially grant eligible): Building and Waste Sludge Holding Tanks
Miscellaneous: (partially grant eligible)
- Operations Building
- Plant Water System
- Plant Recycle System
- Yard Piping, General Site Work and Electrical Costs
- Multiple non-hazardous supplemental carbon sources (e.g., sugar water, glycerin, etc.)
- Alum Feed System for phosphorus removal
Post Treatment (not grant eligible): UV Disinfection, Post-Aeration, Effluent Flowmeter, and Outfall Extension