Page 425 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

380 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

FIGURE 12.45 Culligan Multi-Techt filtration system as set up at
Colorado State University, 1985, for evaluation of removals of Giar-
dia cysts. (Courtesy of ABWt Infilco-Degremont, Richmond, VA.)
FIGURE 12.46 Automatic backwash (ABWt Infilco-Dregemont)
at Ignacio, Colorado.

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Concrete modules have been constructed up to 4.65 m (50 ft ).
to a filtered water flume on one side that runs the length of the
Parkson listed some 300 installations for industrial water and
filter giving a common tailwater elevation for all cells. Back-
wastewater treatment (Parkson DS1, 1991).
wash is accomplished by a traveling bridge that has a backwash
pump and a ‘‘shoe’’ that fits over the under-drain block for a
12.8.2.2 Deep Bed Filtration—Culligan Multi-Techt
particular cell during the time of backwash. The backwash
The Culligan Multi-Techt came about from the collaboration water source is the flume of finished water. The bridge moves
with Professor E. Robert Baumann (Iowa State University) continuously from one cell to the next and from one end of the
and John Scanlan (Culligan) in the early 1980s. The system bed to the other and back. Figure 12.46 shows an ABWt
was intended for small municipal water systems as a package system as installed for municipal water treatment at Ignacio,
technology, made feasible by modern SCADA systems (the Colorado. The system has been used for filtration of secondary
Culligan had a form of this by the mid-1980s). Figure 12.45 is treated wastewater. An example is at Aspen, Colorado,
a photograph of a system, c. 1985, which was effective in where such a filter is used following secondary biological
reducing turbidity to low levels and in removing Giardia treatment and before discharge of the effluent into the Roaring
lamblia cysts (Horn et al., 1986; Horn et al., 1988). The key Fork River.
components are: a centrifugal pump that pressurizes a system,
a first stage filter of coarse media, and a second stage filter of 12.8.2.4 Package Filtration—EPD Wearnes USAt
graded media, finer than in the first stage. The coagulant is The EPD Wearnes USAt filter system started as a swimming
injected into the first stage. Backwash may be programmed on pool filter in the 1980s (under its predecessor company Envir-
time, on headloss, or turbidity breakthrough. The coagulant onmental Products Division, Hoffinger Industries) and then, in
dosage must be determined by the operator. the early 1990s, after further development, found a market in
small drinking water system applications. The filter system is
12.8.2.3 Shallow Bed Filtration—ABWt two stage, each stage in a cylindrical tank with horizontal axes.
The automatic back wash filtration system (ABWt) was The two tanks are filled with media of garnet to a depth of 305
developed in the 1950s by Hardinge and was later acquired mm (12 in.) with the first stage coarser than the second. For the
by Environmental Elements, Inc. of Baltimore, later assimi- first unit, d 10 ¼ 0.27 mm, UC ¼ 1.6, and for the second unit
lated by Infilco-Dregremont, Inc. (http:==www.degremont- d 10 ¼ 0.18 mm, UC ¼ 1.3. The backwash rate was 37 m=h
2
technologies.com=dgtech.php?article390). The filter has had (15 gpm=ft ) without loss of media. The system is automated
skeptics due to its shallow depth and ostensibly short duration and is backwashed based on pressure, time, or effluent turbidity.
backwash. Despite this the system has been adopted rather Coagulant feed and turbidity and particle counting instrumenta-
widely for both municipal drinking water and for filtration of tion were a part of the ‘‘package,’’ along with a SCADA system.
secondary effluent from biological wastewater treatment. The
bed may be 30 m (100 ft) long 6.1 m (20 in.) wide and is
12.8.3 EVALUATION OF PRODUCTS
divided into cells about 305 mm (12 in.) wide with plastic
partitions. The headwater is the same for all cells and thus the Information on virtually any product is available through
filtration scheme is ‘‘declining rate.’’ The under-drain for a various sources, for example, manufacturer’s brochures,
given cell collects water from that cell only with conveyance Web sites, and manufacturer’s representatives. Trade shows