NC0057193_plan of action_20240521

Complete
Water Services, LLC
Nantahala Outdoor Center
Wastewater Treatment Plant Upgrades
May 2024
The Nantahala Outdoor Center (NOC) plans to expand the current outdoor center. The plan is to
provide a new lodge along with other visitor amenities such as tennis courts, pool, restaurants,
pubs, etc. This is a long-term plan that will be constructed in phases.
Due to the planned construction, NOC will require upgrades and an expansion of their current
wastewater treatment system. NOC currently runs a Sequencing Batch Reactor (SBR) system
for the sanitary wastewater. Upgrades/expansion to the existing plant are the removal of the
SBR system and the addition of a membrane bioreactor (MBR) system. MBRs are well suited for
wastewater treatment plant (WWTP) upgrades being conducted in a phased approach.
Existing WWTP System
The existing WWTP is an SBR system. An SBR is an activated sludge (AS) system that relies
upon standard sludge settling characteristics to provide clarification. The current annual
average flow ranges between 2,000 to 7,000 gallons per day (GPD). Lower flow from
October to May and the higher flow between June through September. On only two
peak days of the summer the system treated a maximum of approximately 11,000 GPD.
The treatment plant is located on the entrance road to the center, directly behind the restrooms
that serve the scenic railway stop.
Basis of Upgraded Treatment System
NOC is developing a Master Plan for the expansion of the facility to include a lodge, special
event venues, bars, restaurants and cabins. Using the master plan as a guide, it is estimated
that, once the full build -out is complete, the maximum wastewater generated would be
approximately 80,000 GPD.
NOC is limited on usable space; therefore, the intention is to install the new OF building on
piers above the existing sludge tank and chlorine contact chamber. The pre-engineered metal
building will be installed with the floor at the same level as the existing SBR tanks. A landing and
platform will connect the new building to the existing platform on the SBR tanks. A new set of
stairs will be installed on the east side of the new building.
Proposed Upgraded Treatment System
The proposed system upgrade for NOC is a new MBR system. The upgrades will reuse much
of the existing system but would be reconfigured. The SBRs would be used as the bioreactors,
with one in use and one as redundant. Waste activated sludge (WAS) would be pumped to the
existing sludge tanks. New equipment would include a rotary screen, pumps, blowers,
ultrafilter (UF) membrane skid, and clean -in -place (CIP) skid. Effluent will discharge back
through the existing chlorination chamber structure and effluent monitoring discharge point.
The new MBR system is also be an activated sludge process; however, it utilizes OF
membranes to separate the biological solids (biomass) from the wastewater rather than
relying on gravity settling as with the existing system. The activated sludge process is by far
the most common treatment process for removing biochemical oxygen demand (BOD)
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Complete
Water Services, LLC
The MBR process includes an aerobic activated sludge bioreactor and a OF membrane system.
The bioreactor will be the converted SBR tanks. The system will incorporate appropriate control
systems including level, flow rate, dissolved oxygen (blower control), and pressure sensors.
The OF membrane system is external to the bioreactor. This configuration makes a much safer
and cleaner working environment than most in -tank MBR systems. The OF system will be
installed in a building located above the existing sludge tank area, with the building floor the same
level as the platform across the existing SBR tanks. The skid modules are a completely sealed
unit and the membranes are cleaned automatically.
The OF system is modular. Initially, there will be one 6-pack skid. The skid is capable of treating
up to 40,000 GPD. The pore size of the OF is 0.03 micron. Therefore, the discharge (permeate)
will be virtually free of any suspended or colloidal solids, and extremely low in BOD.
As the outdoor center expansion progresses, additional modules and skids can be added to treat
the additional wastewater. As the wastewater flow increases during the expansion, the
concentration of biomass in the bioreactor will increase to accommodate the additional loading
and more modules are added to the skids to increase capacity.
Treatment System Description
Current infrastructure for the influent to the treatment system would remain. Existing pumps will
pump the wastewater through the existing piping to the area of the new screen, which will be the
west SBR tank. This piping would be intercepted on the north side of the tank and rerouted to a
new rotary screen located adjacent to the tank, in northwest corner. The screen would be located
on a platform so that the wastewater can discharge into the BR tank. Screened solids would fall
into a small roll -off or cart.
The new BR would be fitted with an aeration grid with diffusers, duplex blowers, dissolved oxygen
probe, level transmitter and submersible pump. Treated wastewater with the biomass would be
pumped up to the OF membrane skid, located in the new building. Concentrate (biomass) would
discharge back into the BR tank as Return Activated Sludge (RAS) or to the existing sludge
digester tank as waste activated sludge (WAS). Permeate would either be routed back to the BR
as permeate return or discharge through the existing chlorine contact chamber and then into the
existing effluent chamber for discharge to the Nantahala River.
Since the membranes are modular and run in parallel, individual modules can be kept onsite as
spare/redundant parts. Due to lack of area footprint for plumbed spares, spare pumps will kept
onsite.
WAComplete Water\2024\Proposals\Nantahala Outdoor Center\MBR Proposal with Elevated Building\Nantahala Outdoor Center WWTP MBR Upgrades Description.docx
340 Cherokee Street Marietta, GA 30060 • Voice: [phone] • Fax: [phone]

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