Civil Engineering Reference
In-Depth Information
TABLE 15-7. Summary of Pilot Plant Results—Erie, Colorado
Constituent
Microfiltration
Ultrafiltration
1. Turbidity
goal:
0.1
0.1 in 99%
0.1 in 99%
2. Microorganisms
goal: 4 Log
8 Log
7 Log
3. THMFP
goal:
80
g/L
130
g/L
135
g/L
4. TOC removal
goal: 20%
Carter—21%
50/50—18%
70/30—11%
Erie
Carter—23%
50/50—19%
70/30—19%
Erie
— 7%
—10%
5. CIP interval
goal: 14 day min.
Carter: 30 day
Erie: 14 day
Carter: 30 day
Erie: 3 day
6. Estimated annual O&M
$0.35 / 1,000 gal.
$0.56 / 1,000
(Courtesy of Erie Public Works Department)
membrane filtration, GAC treatment, and chemical addition in a pressurized system so
that water flows to the new clearwell without additional pumping required. The waste
system utilizes several options for the plant operators to recover or recycle settled
backwash waste in the process or as irrigation water. Sludge waste is discharged to a
sanitary sewer.
NANOFILTRATION AND REVERSE OSMOSIS
Introduction
Reverse osmosis (RO) membranes first became commercially available in the 1960s
for treating seawater and brackish water. Today, RO is the most common type of
membrane process for potable water production in the United States, though it is
generally used for smaller plants. Nanofiltration is a much newer category of
membrane filtration with relatively few installations but rapidly growing interest in the
technology.
RO and NF membranes can separate a large spectrum of contaminants from water,
including turbidity, pathogens, salts, hardness, heavy metals, and natural and synthetic
organics. The only substances that are not typically separated by membranes are dis-
solved gasses.
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The advantage of RO and NF is that they remove substances at the
molecular and ionic levels, removals that UF and MF membranes are largely incapable
of. However, RO and NF membranes require much higher operating pressures than
UF and MF membranes.
Typical Applications
RO is most commonly used for desalination of brackish waters in the United States,
where there are over 140 operating plants.
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The lower salt concentrations of brackish
water allow for more efficient treatment of brackish water as compared to seawater.
Generally, RO is not cost effective for large-scale treatment of seawater in the United
