NC0024571_WWTP Operational Changes_20110303

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March 3, 2011
Ms. Belinda Hinson
NCDENR
225 Green Street, Suite 714
Fayetteville, NC 28301-5043
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Subject: City of Lumberton, WWTP Operational Changes
Dear Ms. Hinson:
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MAR 0 9 2011
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The purpose of this memo is to inform you of some operational changes in Lumberton's wastewater
plant. It is my understanding that Jon Locklear verbally notified your office prior to the changes being
implemented. Fora better understanding I believe a brief overview of the last few years may help.
As recently as 2001 we had several major industries and treated a daily flow of 8-9 mgd. As industries
began to close the hydraulic and organic loading placed the plant was well outside the normal operating
windows on many key parameters. These included DO, F/M ratio, detention time for aeration and
clarification, surface loading rate, wier overflow rate, etc. All of these impact the treatment efficiency
and cost.
To address the issue we reduced the number of mechanical aerators and rotated those units in and out
of service as dictated by treatment requirements. As flow levels decreased we took one aeration basin
out of service. Don Register was involved in these efforts and actually used Lumberton's strategy as a
model for other plants.
At this point our flow has dropped to an average of about 5 mgd. From an operational point we simply
do not have the hydraulic load or organic load to support all the treatment units found at the Lumberton
plant. Accordingly, we have taken another aeration basin out of service and we intend to cycle units in
and out of service as dictated by load. None of the units taken out of service will be modified to prevent
being put back into service. All of the equipment will be exercised and maintained to remain available
for the treatment of wastewater if needed.
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From an operational point we gather strict process control information on the system daily. We also
monitor microbial activity and population daily. Should there be a need or in the event of some
impending situation such as a hurricane we will be ready to start up any or all treatment units as
necessary to maintain compliance with the NPDES permit. But quite honestly,_ we_ cannot afford to
operate units just for sake of operating. The electrical savings at the treatment plant are averaging
about $500,000 per year. Our budget has been impacted by the economy of our nation as has the State
budget. But, aside from the economic impact, operating all of the units will not allow the plant to
operate within the ranges for treatment specified in the Sacramento Manual and recognized in the
industry as normal and acceptable.
The plant holds a permit for 20 mgd and we need to keep this in place in accordance with the
equipment we have. No equipment will be removed and we will continue to be bound by the NPDES
permit. It is our hope that the economy will turn at some point and growth will occur or some industries
will chose to locate here at which time we will be in position to accommodate their utility needs.
We provide this for information only and welcome any advice or assistance you may wish to provide.
Thanks much for your time.
Sincerely,
t
Jim Walters
Deputy Director, Public Works
C: Dana Foley, T. Wayne Horne, Rob Armstrong, Jon Locklear
215 Z. &daz Zturt • (D. 23ox 1388 • 1uing.ton, clVoxtt eawtina 28359 • fione 910-6713851 • ¶ax 910-671-3884