Page 656 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Disinfection 611

of 35 g O 3 =kWh. Also in 1933, the St. Maur WTP in Paris As an update to Table 19.2, 12 water treatment plants
3
was expanded to treat Q ¼ 208 m =min of water. Because of serving water to Paris and environs were stated by Langlais
difficulties with a new refrigerated drying system, and the et al. (1991, p. 6) to have an ozone generating capacity
war, the plant did not start operation until 1953. The average of >500 kg O 3 =h (12 metric tons=day) using air as the feed
3
ozone dose was C(O 3 ) ¼ 1.1 mg=L. Energy consumption was gas for treating Q(12 plants) ¼ 3,000,000 m =day water for
39 W h=g dissolved ozone, which included 12 W h for >10,000,000 people. Among the facilities was the Choisy-
compressors, and 6–8 W h for refrigeration. The plant le-Roi, the second largest ozone plant worldwide with an
included 16 contact columns with a cross-sectional area of output of 160 kg O 3 =h. The Neuilly-sur-Marne WTP with a
2
14 m and an effective contact depth ¼ 6.3 m. Both water and generating capacity of 140 kg O 3 =h had generators with
ozone movement was in an upward direction. At the design outputs of 30 kg O 3 =h=generator, and were the largest ozone
generators. As of 1990, over 700 water treatment plants in
flow 12 contactors were to be in operation at Q(contactor) ¼
3
17.4 m =contactor, with 4 contactors in reserve. Two types of France used ozone. To provide a more specialized forum for
ozone generators, each used for half the flow, were used: (1) the exchange of knowledge on ozone, the International Ozone
plate generators operated at 18,000–20,000 V, producing Institute, later known as the International Ozone Association,
1,600 g ozone=h while consuming 35 kW power giving an was formed in 1973 at the First International Symposium on
ozone production rate of 45.7 g O 3 =kWh; (2) tubular gener- Ozone for Water and Wastewater Treatment (Loeb, 2002).
ators operated at 10,000 V, producing 1,600 g ozone=h while
consuming 25 kW power giving an ozone production rate of
19.2.3 CHLORINE DIOXIDE
64 g O 3 =kWh, with C(O 3 ) ¼ 2–3mgO 3 =L. The St. Maur
WTP produced about one-third of the Paris potable water Although Sir Humphrey Davy (Masschelein, 1992, p. 170)
supply. Absorption of ozone was 0.6–0.8 fraction of ozone discovered chlorine dioxide, ClO 2 , in 1811, its first use in
applied. For the counter-current operation, the absorption water treatment was in 1944 to control phenolic tastes and
efficiency was about 0.9–0.95 fraction (Hill and Rice, 1982). odors at the Niagara Falls WTP. A 1956 survey indicated that
The four largest water treatment plants at Paris are listed in of the 56 plants using ClO 2 , most uses were for taste and odor
Table 19.2 and have a combined ozone generating capacity of control; the other uses were for algal control, 7 plants; iron
8.7 metric tons=day. The plants and the date of being put and manganese removal, 3 plants; and disinfection, 15 plants.
online are listed along with the flows for each plant and the In 1977, about 100 plants were using chlorine dioxide, but
ozone concentrations used. At each plant, ozone is added: (1) mostly for taste and odor control. By 1986, however, 300–400
to the raw water to give C(O 3 ) < 1mg=L before storage for plants were using it for disinfection (Anon., 1986, p. 33), and
2–3 days; (2) then again as before coagulant chemicals are by 1997, about 500 plants in the United States were using
added; (3) after sand filtration to give C(O 3 ) ¼ 0.4 mg=L and ClO 2 . In Europe, several thousand utilities used ClO 2 , mostly
t ¼ 10 min. The treatment included GAC adsorption, followed to maintain a disinfectant residual in the distribution system
by chlorination and dechlorination. The C(O 3 ) ¼ 0.4 mg and (Anon., 2001, pp. 1–4). Attributes of ClO 2 included (Aieta
t ¼ 10 min, that is, Ct ¼ 4, was predicated on inactivation of and Berg, 1986, p. 62): its effectiveness being comparable to
polio types 1, 2, 3 at log R ¼ 3 (i.e., 99.9% reduction). The HOCl; effective for 6.0 < pH < 8; oxidizes NOM but without
intent of the multistage ozonation was to react with organics the formation of disinfection by-products; does not react with
in the first stage, the purpose of the second stage was to aid in ammonia; maintains residual in the distribution system, it is
coagulation, and the third stage of ozonation was for primary generated onsite.
disinfection and further oxidization of the residual organics
(Hill and Rice, 1982).
19.2.4 ULTRAVIOLET RADIATION
The source of UV radiation is mercury vaporization; this
phenomenon was discovered in 1835 and in 1901 the mercury
TABLE 19.2 vapor lamp was developed (Snicer et al., 2000, p. 6). The first
Ozone Generation at Four Largest Plants for Paris, application of UV for disinfection of drinking water was in
c. 1972 Marseilles, France in 1910; the system was not reliable due to
its complicated technology and was not used since ozone
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Plant Date Q (m =min) C(O 3 ) (mg=L)
came on the scene in Europe, along with chlorine in the
Méry-sur-Oise 1965 208 3.6 United States. The emergence of DBP’s in the 1970s stimu-
Orly 1966 208 4.0
lated a more concerted search for disinfectants other than
Choisy-le-Roi 1968 626 3.0 chlorine.
Neuilly-sur-Marne 1972 415 4.8
In the 1980s, Professor Günther Schenck of the Max
Planck Institute for Radiation Chemistry and Professor
Source: Adapted from Hill, A.G. and Rice, R.G., Historical background, 2
Heinz Bernhardt found that radiant exposures 400 J=m
properties and applications, Chapter 1 in Rice, R.G. and Netzer, A.
(Eds.), Handbook of Ozone Technology and Applications, Volume 1, could inactivate viruses and bacteria (Hoyer, 2000a, p. 22).
Ann Arbor Science Publishers, Ann Arbor, MI, 1982, p. 17. At the same time, that is, in the 1980s, regulatory factors
started to influence the development rate of the UV