Civil Engineering Reference
In-Depth Information
GAC is an ideal medium to support biological growth following ozonation. For a
complete discussion of biologically active filtration using GAC, the reader is referred
to Chapter 12, ''Filtration.''
EXPERIENCES WITH ACTIVATED CARBON
Activated carbon has been used successfully at many treatment plants on a continuous
and interim basis. Several applications are presented in this section. The reader should
exercise caution when extrapolating experiences from one application to another, since
specific objectives vary from plant to plant. The experiences reported here serve as
examples only.
Real-World PAC Example: Omaha, Nebraska
Metropolitan Utilities District (MUD) of Omaha, Nebraska, operates a 158-mgd (598-
ML / d) water plant that takes water from the Missouri River.
32
Figure 17-12 is a flow
diagram of the Florence Water Treatment Plant. The water is split-treated with half
lime softened and half alum coagulated. PAC can be added before the presettling basin
or with alum before the settling basins.
MUD uses PAC mainly during the spring when snowmelts cause tastes and odors.
In addition, PAC is used during a large rainfall event or when high runoff causes
increased turbidities. Current operating practice is to maintain a polishing dose of 6
Chlorine
Alum
Missouri
River
Polymer
Alum
Clarification
Presedi-
mentation
Basin
Intake
Screens
Mixing
Basin
Contact/
Settling
Blending
Basin
Softening
PAC
PAC
Chlorine
Lime
Chlorine
Blending
Basin
Mixing
Basin
Settling
Basin
Settling
Basin
Filters
Storage/
Distribution
Fluoride
Fluoride
Fig.
17-12.
Metropolitan
Utilities
District,
Omaha,
Nebraska,
water
treatment
plant
flow
schematic
