Civil Engineering Reference
In-Depth Information
TABLE 15-5. Raw Water Data for the Erie Water Treatment Plant
Constituent
Units
Carter Lake
Erie Lake
Turbidity
Average / Maximum (NTU)
3 / 8
5 / 200
Total organic carbon
Average / Maximum (mg / L)
3 / 5
4 / 6.5
THMFP
g/L
137
Total suspended solids
Average (mg / L)
6
55
Temperature
Average / Minimum (
F)
50
/42
60
/33
pH
Range
6.8-9.2
7.0 -9.1
Alkalinity (mg / L as CaCO
3
)
Range
30-40
95-110
Hardness (mg / L as CaCO
3
)
Range
20-24
100-130
(Courtesy of Erie Public Works Department)
water from the deep, high mountain reservoir Carter Lake and supplies a consistently
high-quality water.
The MF membrane tested was a polypropylene material nominally rated at a 0.2-
micron pore size. The system was operated in a dead feed flow configuration, and
utilized an air / raw water backwashing system. The UF membrane tested was a poly-
sulfone material nominally rated at 0.05-micron pore size. The UF system was operated
in a cross-flow configuration and utilized a sodium hypochlorite backwash using fin-
ished water. Both units required periodic chemical cleaning with a caustic cleaning
solution and alternating citric acid cleanings.
The goals of the pilot study were: to identify the membrane life-cycle costs; to
develop reliable operation and maintenance cost projections; to compare the opera-
tional and maintenance requirements of each manufacturer's system; and to evaluate
the treatment options for the removal of TOC by use of chemical coagulation (alu-
minum chlorohydrate (ACH)), granular activated carbon (GAC) contactors, and the
adsorbent heated iron oxide particles (HIOPs).
Pilot Test Results
Results of the pilot testing for both the UF and MF membrane
operation are summarized in Table 15-6. As expected, the MF membrane system has
a much higher flux and production rate than a UF system.
TOC reduction through the membranes was evaluated in the first 60 days of the
pilot study. Several data points were taken from each unit using the four raw-water
scenarios. Figure 15-14 shows the quantity of TOC in the raw water as compared to
that of MF- and UF-treated water. The Erie Lake source has a low ratio of UV-254 to
DOC, identified as the source's SUVA value. A low SUVA value (between 2 and 3)
indicates that the TOC is largely dissolved organics and therefore would pass through
the membrane without being removed. The Carter Lake source has a slightly higher
TABLE 15-6. Operational Results from Erie Lake Pilot Study
MF
UF
Operational flux rate
74 gfd at 50 gpm
16 gfd at 4 gpm
Feed water recovery
90% at 45 gpm
86% at 8 gpm
Backwash frequency
30 min
30 min
(Courtesy of Erie Public Works Department)
