San Mateo Treatment Plant Study

From: Ken Poulton (poulton)
Date: Fri Feb 14 1997 - 09:37:16 PST


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Date: Fri, 14 Feb 1997 09:37:16 -0800 (PST)
From: Ken Poulton <poulton>
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Subject: San Mateo Treatment Plant Study
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>From Kckarmendy@aol.com-DeleteThis Fri Feb 14 09:00:43 1997
>From: Kckarmendy@aol.com-DeleteThis
Date: Fri, 14 Feb 1997 11:55:44 -0500 (EST)
Subject: Re: San Mateo Coliform Study

         City of San Mateo Water Quality Control Plant
     Study to Evaluate Alternative Effluent Coliform Limits
=0D

On behalf of the City of San Mateo, I would like to bring the sailboard c=
ommunity up to date on
the study we are implementing to evaluate alternative effluent coliform l=
imits. My name is Kacey
Karmendy, and I am the Laboratory Supervisor for the City of San Mateo's =
Wastewater
Treatment Plant. This study is based on workplans previously approved by=
 the Regional Water
Quality Control Board (RWQCB) staff for the South Bayside System Authorit=
y (SBSA), East Bay
Dischargers Authority, Central Contra Costa Sanitary District, San Franci=
sco, East Bay
Municipal Utilities District, and Central Marin Sanitation Agency. Recei=
ving water monitoring in
the studies completed to date has documented that beneficial uses remaine=
d fully protected
when the treatment plants operated with fecal coliform limits of 200 to 5=
00 MPN/100 mL. =

Operating at this level of disinfection also benefitted water quality due=
 to the associated
reduction in chlorinated hydrocarbons (disinfection byproducts) discharge=
d to the Bay.
=0D
The Basin Plan fecal coliform water quality objective is a log mean of 20=
0 MPN/100 mL for
water contact recreation. The San Mateo Wastewater Treatment Plant disch=
arges an advanced
secondary effluent into the deep water channel through a diffuser about 3=
400 feet offshore in
about 40 feet of water. The outfall is designed to provide an initial di=
lution of about 40:1. Dye
and drogue studies conducted for the RWQCB Shellfish Program showed subse=
quent dilution
of 10:1 to over 50:1.
=0D
The intent of the study is to demonstrate that water contact recreation o=
bjectives will be fully
protected when chlorinating the effluent to a 240 MPN/100 mL fecal colifo=
rm level. The study
will take up to six months, to allow evaluation of plant disinfection per=
formance under both wet
and dry weather conditions. Initial receiving water monitoring will be c=
onducted once per week,
increasing to twice weekly (weather permitting) when target coliform leve=
ls are achieved. In
addition, the wastewater plant effluent will be monitored daily for total=
 and fecal coliform. In the
unlikely event that receiving water objectives are exceeded due to factor=
s attributable to this
study, chlorine dosages will be returned to previous levels.
=0D
The six receiving water stations are as follows:
     WS-A: directly over the San Mateo WQCP outfall diffuser located =
just north of the San
               Mateo Bridge at the west end of the deep water channel.
     WS-B: 100 yards NW of diffuser along west edge of channel.
     WS-C: midway (~750 yards) between the diffuser and channel marke=
r 8A along west
               edge of channel.
     WS-D: at channel marker 8A, in the channel side of the marker.
     WS-E: 1000 yards from marker 8A on a course 189 degrees magnetic=
=2E This is
               approximately halfway between the windsurfer launch area a=
nd 8A.
     WS-F: 1000 yards NE of SBSA outfall (reference station)
=0D
This monitoring plan was approved by RWQCB staff in November, with input =
from Peter Candy,
a representative of the sailboarding community. The chlorination reducti=
on program was
initiated in early January at the treatment plant, and receiving water mo=
nitoring began soon
after. Initial data show fecal coliform far below the receiving water ob=
jective, even with all the
storm flows into the Bay. Those who wish additional information can cont=
act me, Kacey
Karmendy, at (415)377-4698 or e-mail to kckarmendy@aol.com.-DeleteThis
=0D
I would also like to take a moment to comment on an article from your Sep=
tember, 1996,
newsletter. Peter Candy wrote an informative piece on the then-proposed =
study plans by SBSA
and San Mateo. Some of the issues mentioned below were discussed during =
a meeting
between City representatives and Mr. Candy in late October.
=0D
"A reduction in chlorine means a corresponding increase in pathogenic bac=
teria discharged to
the Bay, an obvious health threat."
While there is the potential for an increase in pathogens, in reality we =
have to overdose
significantly with sodium hypochlorite to meet our stringent discharge re=
quirements. Studies by
other treatment plants have shown that reduction of chlorination had no a=
dverse impact on
receiving water, and, in fact, on the treated wastewater itself.
=0D
"Residual chlorine levels in the final effluent range in the order of 2 t=
o 5 milligrams per liter."
We are required to have 0.0 mg/L chlorine residual in our effluent. The l=
evels indicated above
are prior to dechlorination.
=0D
"If the SMWQCP...permit(s) are to be amended to allow bacterial discharge=
s to exceed current
Basin Plan limits..."
The Basin Plan limit, as stated above, for water contact recreation is a =
log mean of 200
MPN/100 mL. We would only ask to meet that standard at the end of the pi=
pe (in other words,
at the final effluent), disregarding the obvious dilution once in the rec=
eiving water.=

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