Item 3 - Water Treatment and Quality (2) *AGENDA REPORT • . .W
CITY OF POWAY
Cm,!N THE GO\3?'
TO: Honorable Mayor and Members of
the City
FROM: James L. Bowersox, City Man
INITIATED BY: Alan D. Archibald, Director Public Services Ori
DATE: January 30 , 1986
SUBJECT: Water Treatment and Quality
BACKGROUND
Several months ago, the Council expressed concern over the reduc-
tion in water quality when our Water Treatment Plant is operated
at its design limits to supply water to both the City of Poway
and the Ramona Municipal Water District.
Our present agreement with the San Diego County Water Authority
calls for the delivery of a maximum of 8 Million Gallons Per Day
(MGD) of treated water to the Ramona Municipal Water District.
The treatment plant is designed to treat 24 MGD, but has a maxi-
mum capacity of 30 MGD by increasing the chemical dosages and
filtration rates. In 1985 , our maximum day production, includ-
ing Ramona, was 23. 2 MG and our peak production rate, which
lasted for a four-hour period, was equivalent to 29.8 MGD. Those
flows occurred during the month of July.
During the peak production periods, chemical dosages were
increased by up to 50% to control turbidity. The turbidity of
the treated water during this peak period rose from a normal
reading of 0 .12 Nephelometric Turbidity Units (NTUs) to between
0 .17 and 0 .22 NTUs, since the floc created by the addition of
alum is not heavy enough to settle out during the pretreatment
process. However, this is far less than the State Health
Department' s standard of 0 . 50 NTUs.
Since July, we have been experimenting with polymers to increase
the coagulation of impurities during the pretreatment process ,
and thereby lowering the need to use alum as a coagulant.
During our experimentation, we have found a ploymer that
has lowered our overall chemical usage by 33%. With the
use of this polymer, and the reduction in alum usage, we
will be able to produce water during the peak periods with
very little loss in overall water quality, since the heavier
ACTION:
Accepted report.
M. Wahlsten, City Clerk
JAN 3 0 1986 ITEM 3 //
410
Water Treatment
Page 2
January 30, 1986
floc produced using the new polymer will settle out during the
pretreatment process and does not overload the filters .
Consequently, with this chemical change in our water treatment
process, we will be able to continue to provide Poway citizens
with the highest quality of water even during peak production
periods .
RECOMMENDATION
It is recommended that this report be received and filed.
JLB:ADA:pw
JAN 3 0 1986 ITEM 3