NC0062855_5 Day Written Report_20110324

Mar. 24. .2011 9:38AM . No. 9167 P 1
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Mar. 24. 2011 9:38A(i . No. 9167 F. 2
Mayor Theron K. Bell
Commissioners;
Lynn M. Loy, Mayor Pro Tem
A. H. Davis Jr.
Terri Holt
Joey Boswell
Claire A. $arrow
March 24,2011
NCDENR
NCDWQ
. 225 Green St, Suite 714
Fayetteville, NC 28301-5043
TOWN V OI Ro_B. A..NS
PO Box 296
Robbins, NC 27325
[phone]
Fax: [phone]
RE: WWTP Spill/Upset 5-Day R.eport
Robbins WWTP, Moore County
NPDES Permit Number: NC0062855
Dear Enforcement Authority,
Town Manager
George Hayfield
This letter is official response for the caustic spill at Robbins WWTP. The following
describes the chain of events and steps taken to rectify the situation.
The 100 gallon caustic day tank in the chemical room inside control building
overflowed 50% caustic soda to the floor drain which leads to splitter box. This goes .into
Aeration Basin #2 and this was the Basin in use at the time. Aeration Basin #1 was 50%
full and not in use. This caused in very high PH in Aeration Basin #2 which effectively
killed all microorganisms therefore resulting in greatly reduced treatment of water. The
spill was a slow overflow that reached floor drain Saturday afternoon 3/19 then was
discovered when I came in Sunday 3/20 at about 3:00 pica. The reason it overflowed was
the fill valve was unknowingly not completely shut on Saturday by operator in training
when caustic tank was filled back to 100 gal. It continued to fill at very slow pace but
enough to overflow. It was filled about 2:30 pm Saturday. Caustic soda probably
reached Aeration Basin #2 by roughly 4:00-5:00 prn. I estimate the total amount spilled
to be 600 gallons over roughly a 24 hr. period.
When I first became aware of incident on 3/20, besides stopping the caustic. leak, I
immediately ran ph tests in sections 1 and 4 of Aeration Basin, RAS and. Effluent.
Efflhent ph was still good at 7.00. Section 1 of Aeration Basin was up to 12.3ph and
section 4 was 9.5ph. I then increased RAS rate to get relatively lower ph and bugs over to
head of plant to help buffer and to try and possibly save the treatment process. I then
increased my Alum feed rate from 10 gal/day to 20. I ran several settleometer tests and
kept a check on clarifier blanket. Both indicated sludge was still settling out although
higher than normal and the water was slightly dingy through the column. Effluent water
was somewhat cloudy and darker colored. I ran an ammonia test and it was 2.28 and this
is higher than usual. I slowly drained out of service Aeration Basin #1 over to Aeration
Basin #2 in order to get any good bacteria there and possibly buffer ph. Aeration. Basin
#1 was still high at around. 9.5 because it was used to contain 2.00 gallons of caustic

Mar, 2a. 2011 9 : 39AM
N —9167 P.
slowly drained there in December when we replaced a snick valve on outside of caustic
bulk tank line, I continued to operate this way until about 11.:00 pm when I left. I arrived
back to plant at 5:30 am the next morning and took ph samples right away. At this point
the Effluent was 9,0ph, Af32/1 was 10.lph and:AB2/4'was 10.5ph. The Basin ph had
come down and seemed to hold atthis point but the effluent eventually peaked at 10.1ph
at about 1:00 pm. I did. turn the chlorine feed up from2..5 lb./day to 4 lbs. to help slightly
lower ph, Sludge tests indicated sludge still settling out good but water was very rust
colored and dingy. I notified the state at around 11:15 am on Monday 3/21 and spoke
with Dale Lopez who then got me in contact with Pa:uI Rawls. I explained situation to
hint and.he suggested a couple of things to try but after doing so and. examining mixed
liquor under microscope it appeared to be a total kill of microorganisms. At 2:00 pm I
sent all flow to Aeration Basin. #1 which by now was only about 15-20% full and no
further effluent discharge was made after this point. 1 plan fill Aeration Basin. #1. with all
influent flow to around 60-70% and then re -seed.. 1 plan to get the seed from Troy
WWTP. Influent flow is down to 0.100 MOD so it should take a day Or two to reach this
point. I have the drain cracked open on Aeration Basin #1 section 4 to help circulate
water back to head of pl.aiit as RAS. At this point I expect to have plant hack on line and
discharging by the weekend or very early next week based on my current flow. I will
continue to monitor bacteria and treatment very .closely during this time to see how the
reseeding in working. DWQ Fayetteville will be notified when the exact time of
discharging is expected to start.
The preventative measures being taken to prevent this from happening again are •
placing a spill containment area around both Caustic and Alum day tanks. This should
contain any leak from day tank and even a small overflow if valve was left cracked open.
Secondly we will look into spring loaded valves for tilling of day tanks so an operator
will have to stay at valve while filling; Thirdly we will see if it is possible to relocate
drain or use a removable block for the drain.
Because of this event we were in noncompliance of pernnit•for ph and temperature
because the reading for 3/21 was 10.1 and there was no temperature taken on 3/21 as
well.
Paul Rawls from DWQ came to inspect the situation on Tue. 3/22. A close
examination of the plant was done and well as inspecting the downstream river sample
site to inspect for any possible aquatic damage but there was no apparent evidence of
that. I will be keeping him and. DWQ tip to date on the progress of plant and hopefully
everything will he back to normal operation as soon as possible. Please contact me if any
further information is needed.
Sincerely,
Rodney L. Kiser
Robbins WWTP Manager/ORC