Page 477 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

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

finest grade of diatomite, that is, Filter-Celt, but then were
only 1-log for the coarsest grade, that is, Celite 545t.
In another case, that is, another raw water, using both
Hyflo Super-Cel and Celatom FW-12 (which are comparable
grades as seen in Table 14.1), turbidity levels were reduced
from about 0.9 NTU in the raw water to <0.10 NTU in the
2
filter effluent for HLR ¼ 2.44 m=h (1 gpm=ft ), body feed ¼
2 2
5mg=L, and pre-coat ¼ 1.0 kg=m (0.20 lb=ft ) (Ongerth and
Hutton, 2001).

14.2.1.2 Particle Counts
Using Celite Hyflo Super-Celt and Celatom FW-12t, particle
counts were reduced from about 4100–4500 #=mL in the raw
water to 105–250 #=mL in the filter effluent for HLR ¼ 2.44
2
m=h (1 gpm=ft ), body feed ¼ 5mg=L, and pre-coat ¼ 1.0
2
2
kg=m (0.20 lb=ft ) (Ongerth and Hutton, 2001). As with
turbidity, particle count removals are dependent upon the
particular water being filtered.
5 μm
14.2.1.3 Iron and Manganese FIGURE 14.8 Cysts of G. lamblia. (From Walton, H.G., Diatomite
Representative concentrations of soluble iron and manga- filtration: Why it removes Giardia from water, in Wallis, P.M.,
nese in ambient waters are perhaps 4–8mg=LFe 2þ and and Hammond, B.R. (Eds.), in Advances in Giardia Research,
0.3–1.5 mg=LMn 2þ (Coogan, 1962, p. 1509). The oxide University of Calgary Press, Calgary, Alberta, Canada, 1988. With
t
forms, for example, Fe 2 O 3 and MnO 2 , are particulate, which permission; Courtesy of Celite Corp., Lompoc, CA.)
may be removed by DE filtration. Iron may be reduced to
0.2 mg=L (Coogan, 1962, p. 1514); data are not available
for MnO 2 .
14.2.1.5.2 Cryptosporidum oocysts
14.2.1.4 Asbestiform Fibers In a study of removals of Cryptosporidium oocyts using
Walton test filters (a bench-scale flow-through apparatus
Two kinds of asbestiform fibers are found in Lake Superior 2
with a septum area of 15 cm ), Ongerth and Hutton (1997)
near Diluth at levels up to 17 million fibers=L for total fibers.
5
4
Amphibole fibers were about 10 –10 fibers=L and chrysotile found
fibers numbered 10 5 fibers=L. Removals by DE were Celite 512t Celatom FW-6t 6.03 log R(Cryptosporidium) 6.53
100% and perhaps 70%–80%, respectively, achieved using Celite Hyflo Celatom FW-12t 5.79 log R(Cryptosporidium) 6.12
either C-512 or Hyflo Super-Cel with alum coating Super-Celt
(Baumann, 1975, p. 12). Celite 535t Celatom FW-50t 3.60 log R(Cryptosporidium) 4.51
By comparison, for rapid filtration, removals are on the order
14.2.1.5 Biological Particles
of 3.0 < log R(Cryptosporidium) <4.0.
Removals of biological particles depend on both their size and
the grade of diatomite. Removals of cysts, oocyst, bacteria, 14.2.1.5.3 Bacteria
and viruses have been determined in various investigations
since about 1972 (with the first being the assessment of Removals of bacteria (E. coli) were dependent on grade and
removals of E. histolytica cysts by the U.S. Army in 1944 whether alum or polymer was added (Schular and Ghosh,
(see Section 14.1.5.1). 1990, p. 71). Removals were Celite-512t ¼ 3-log; Celite-
503t ¼ <1-log; Celite-545t ¼ 1-log. The addition of alum
14.2.1.5.1 Giardia Cysts increased removals for all grades >1-log; addition of anionic
polymer increased removals to near 2-log.
Figure 14.8 is an electron photomicrograph of cysts of
G. lamblia; as is well known, the cysts are about 5 mm wide
by 10 mm long, confirmed in the photograph. Also, the cysts 14.2.1.5.4 Viruses
are remarkably consistent in size and shape. Based on numer- Virus removal by DE is effective only with alum (or ferric
2 2
ous tests, seeding a 0.09 m (1.0 ft ) septum area pilot plant ion) or a polymer (Malina et al., 1972). T-2 bacteriophage was
6
generally with 1 10 cysts, none were detected in the efflu- removed 100% by 2% alum coating of Hyflo B. Then, a
ent; based on calculated detection limits, log R 3 even for virulent strain, Mahoney Type I polio virus, was found to
be removed 100% by Hyflo, based on pretreatment with
the coarsest grade of diatomite, that is C-545t, and for 2.44
2
HLR 9.76 m=h (1.0 HLR 4.0 gpm=ft ) (Lange et al., 0.14 mg=L Dow C-31 polymer or with 0.5 mg C-31 per
1984, 1986). gram of Hyflo. Operating conditions were pre-coat