Page 475 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

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

(3) effluent turbidities have been <0.1 NTU consistently; The area of the diatomite tank collection does not include
2
(4) at 3.7 m=h (1.5 gpm=ft ), the filter runs have been 4–5 the pre-coat and body-feed tanks, pumps, piping,
days (before reaching terminal headloss; (5) the spent DE diatomite storage, waste storage, etc. The area for the
rapid filters is for the filtration bed area only; gullets,
could be reclaimed; and (6) waste DE, since there is no
pipe gallery, chemical storage, etc., are not included.
chemical coagulant added, can be disposed of in a land fill.
The diatomite filtration system would require less area for
About 1990, the engineering firms had some questions about
appurtenances than would the rapid filtration system.
the selection of diatomite filtration by their predecessors. In
the meantime, New York had been feeling pressure, mostly
14.1.4.3 Research
from EPA, to filter their Croton water supply. In 1998, how-
ever, the discovery that UV254 would render C. parvum Just after the initial research for drinking-water applications in
oocysts nonviable made moot the question of filtration. 1943, the U.S. Army Engineering Research and Development
Thus, UV disinfection was the technology selected. Laboratories (ERDL) at Fort Belvoir, Virginia, supported
contracts to universities and equipment manufacturers to
develop further the diatomite filtration process. Then, in
Example 14.1 Comparison of Footprints for DE
1979, the Environmental Protection Agency, the legislative
and Rapid Filtration
mandate to develop enforceable standards for drinking-water
quality, reopened the diatomite filtration research.
Given
The full-scale diatomite filtration system for the Croton water 14.1.4.3.1 Process Research 1950–1970s
supply was to have had 48, 2032 mm (80 in.) diameter, DE
2
2
filters, each with 140 m (1500 ft ) septum area, arranged in Academic research started in 1946 (Baumann, 1957) at the
2
12 clusters with HLR(max) 6.12 m=h(2.5gpm=ft ). University of Illinois under the direction of Harold E. Babbitt
and E. Robert Baumann with funding from ERDL. Based on
Required
Estimate the ‘‘footprint’’ area of the collection of pressure their report titles (Baumann et al., 1965), the research
vessels and compare with an estimate of the ‘‘footprint’’ included such topics as filter septa, pre-coat, hydraulics,
for rapid filters. hydraulic loading rates, compression and effects on permea-
bility, removals of E. histolytica, design and operation
Solution
factors, effect of body feed, effect of prior coagulation on
1 Diatomite system filterability, and economics. This research laid the foundation
1.1 One tank: The footprint for one upright DE filter is for municipal water treatment practice that was developing at
2
A(tank) ¼ pd(tank) =4 the same time; it was the basis for the 1954 doctoral thesis of
2
¼ p2.032 =4 Baumann at Illinois. In 1953 Baumann was appointed asso-
ciate professor at Iowa State University (where he remained
¼ 3.243 m 2
until 1991 when he retired) and continued research in diatom-
1.2 A(cluster): Let the tanks be spaced with 1.000 m ite filtration with colleagues and graduate students on topics
2
between tanks, to give 5.000 m for a cluster, that is, such as vacuum systems, theory of diatomite filtration,
2
A(cluster) 25.0 m . and economic optimization of design, and design criteria
1.3 Total area: Let the spacing between clusters be (Box 14.3).
2.000 m. If the clusters are arranged 4 3, the layout
2
is then 14 m 10 m, that is, A(all tanks) ¼ 140 m . 14.1.4.3.2 Research for EPA Regulatory Support
1.4 Capacity: The total flow for the full-scale plant is
Just as with slow sand, diatomite had a resurgence in interest
Q(plant) ¼ A(septum area=tank) N(tanks) HLR about 1979 due to the fact that giardiasis had become recog-
2
¼ 140 m =tank 48 tanks 6.1 m=h nized as a major waterborne disease. Dr. Gary Logsdon,
3
¼ 40,992 m =h EPA, Cincinnati, was familiar with the 1943 publications
3
¼ 983,800 m =day (260 mgd) concerning the U.S. Army research on the filtration of
E. histolytica cysts and the adoption of diatomite filtration
2 Rapid filtration by the military. Based on the promise of diatomite filtration
2
2.1 HLR: Assume that HLR ¼ 12.2 m=h (5 gpm=ft ) for the removal of Giardia cysts, some initial research was
3
2.2 Plant flow: Q(plant) ¼ 983,800 m =day (260 mgd) done at the EPA labs in Cincinnati along with work at the
2.3 A(filters)
University of Washington, followed by research sponsored
A(filters) ¼ Q(plant)=HLR by EPA at Colorado State University (CSU), facilitated by
3
¼ (983,800 m =day)=(24 h=day)=12.2 m=h personnel at Johns-Manville, Denver (Ray McIndoe and
¼ 336 m 2 AlanWirsig). The CSU research established that all grades
of DE removed G. lamblia cysts and that turbidity removal
Discussion and bacteria removals depended on grade, and that alum or
Comparing areas,
polymer additions to DE body feed resulted in high removals
A(diatomite tank collection) ¼ 140 m 3 for the latter, even for coarse grades of DE (Lange, 1983;
A(rapid filters) ¼ 336 m 3 Lange et al., 1986).