Page 11 - NCRWA Tarheel Pipeline Spring 2013

Photos Courtesy of Mike Cox
Spring 2013 | NCRWA.COM 9
feature
The brine raw water arrives at the plant by
way of a 24-inch pipeline (sized for a future
expansion to 5MGD) from four 1,000 gallon
per minute (GPM) wells screened in the Castle
Haynes aquifer. With a salt content of about
3,000 parts per million (mg/L), the raw water
is still well less saline than ocean water, which
has a salt content of approximately 35,000 mg/L.
John Gregory was quick to explain that this was
one of four major considerations for where the
plant and wells were located as he recalled the
first question he was asked when planning for
the plant began, “So where would you like for
the plant to be located, Mr. Gregory?” asked
one of the engineers. “I want it right beside our
other water plant, of course.” With a chuckle, he
explains that the answer basically came back
loud and clear after a study of the aquifers was
complete, “Sorry, not going to happen; the plant
is going out here.”
Along with the concentration of salt in the
wells, the capacity of the wells, the proximity
to an adequate supply of affordable electricity,
and the proximity to the concentrate (or the
waste product of the plant which consists
of concentrated, salt-laden water) discharge
location were all major variables considered
during the planning. While the first three
variables were well satisfied at the final location,
the discharge location was not. The final
discharge site, the Albemarle Sound, was more
than 19 miles away, quite a length of pipeline
just to discharge the concentrate but required
nonetheless. While this may seem excessive,
the actual pipe laying may have been the least
of the difficulties as just the permitting, gaining
of easements and acquisition right-of-ways
for the discharge pipeline took between 3 to 4
years to complete. It also included a permanent
marker in the Sound for the exact location of
the discharge manifold, which according to Mr.
Gregory, also provides the local fisherman with
a great location for flounder fishing.
Back inside the plant, whichwas constructed
by Mideast Builders from Chesapeake,
Virginia, the primary treatment portion of
the plant includes two 1.0 MGD Harn RO
reverse osmosis skids (or units). These units
basically force the raw water through long
membrane filtration tubes at high pressures,
which separates the permeate (or filtered
water) from the concentrate. The permeate is
then conditioned chemically for pH, hardness,
and other levels before it is disinfected
with sodium hypochlorite and sent out to
ground storage awaiting distribution. While
it sounds relatively simple, the technology
employed and the operations undertaken are
significantly advanced from the traditional
water plants where most professionals gained
their experience.
So the million-dollar-question, or more
accurately the $20 Million question, is just
“...the actual pipe
laying may have
been the least of the
difficulties...”