|
Items in cart [4] |
Questions? Call 888-624-8373 |
PAPERBACK PDF BOOK Free Resources |
||||||||||||||||
|
||||||||||||||||
|
||||||||||||||||
| ||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 4
2
Disinfection Methods and
Efficacy
CURRENT PRACTICES
More than 1.5 billion people in developing nations are still without safe
drinking water. Waterborne diseases such as typhoid, cholera, dysentery,
amebiasis, salmonellosis, shigellosis, and hepatitis A are still estimated
to be responsible for the deaths of more than 30,000 people daily (IRC,
19841. In that context, the United Nations General Assembly has declared
1981-1990 as the International Drinking Water Supply and Sanitation
Decade (WHO, 19841.
In the last century, major outbreaks of waterborne diseases also occurred
in the United States and other affluent nations. Cholera and dysentery
were rampant in the 1800s, and typhoid fever was responsible for about
25,000 deaths in the United States as late as 1900 (Akin et al., 19821.
Current drinking water disinfection practices in the United States pro-
vide the means to control most pathogenic bacteria, viruses, helminths,
and protozoa responsible for the major waterborne diseases. Some out-
breaks still occur in this country (Figure 2-1) owing to continuing problems
involving consumption of untreated water, errors of insufficient or inter-
rupted disinfection, failures to maintain adequate levels of residual dis-
infectant in potable water distribution systems, and/or breaches in the
systems (Akin et al., 19821. Moreover, as discussed later in this chapter,
the etiology of waterborne disease has changed dramatically since the
early l900s; most outbreaks in recent years have been caused by viruses
and protozoan cysts that are generally more resistant to disinfection than
are pathogenic bacteria, the primary targets of concern in past decades.
4
OCR for page 5
Disinfection Methods and Efficacy 5
`~, 50
ye
cc
m
~ 40
o
10
o
it,
.?:?.:?:':?:.?:~.2.
=='/~;'/m'1~''1
/c / ~ / c / ~ I / c' I / ~ / ~ / ~ / I ~ /
FIGURE 2-1 Average annual number of waterborne disease outbreaks occulting in
the United States from 1920 through 1979. From Akin et al. (1982), with permission.
:::- -:~.
~-
.:~::,~,,.,
:.:.::. ·:~
.. ,.
us o / u) / Q ,u, so ~ ~
Regardless of the method employed, disinfection is only one of the
requirements of a potable water supply system. Disinfection requirements
and efficacy are often highly interrelated with other water supply and
treatment operations. A complete system of potable water supply opera-
tions may be considered in three general phases: collection, treatment,
and distribution.
These operations and the principal disinfection practices are briefly
discussed below. The historical development of potable water treatment
and more detailed aspects of disinfection have been reviewed in previous
volumes of Drinking Water and Health (NRC, 1977, l980a,b).
Collection
Surface and groundwater sources of potable water vary locally in terms
of their physical, chemical, particulate, biological, and aesthetic charac-
teristics. Each characteristic may be an important factor in water supply
operations, including disinfection. Water quantity, temperature, pH, sus-
pended particulates, solid aggregates, dissolved inorganic constituents (e.g.,
hardness, ferrous ions, nitrites, and ammonia), nonparticulate organic
OCR for page 6
6 DRINKING WATER AND HEALTH
constituents (e.g., fulvic and humic acids), microbiota (e.g., bacteria,
viruses, protozoa, helminths, and algae), and taste, odor, or color prob-
lems, both natural and anthropogenic, may cause treatment practices ap-
propriate for one set of conditions to be inanorooriate for others.
Treatment
, ~
Besides disinfection, drinking water treatment practices at a given fa-
cility may include coagulation, flocculation, settling, and filtration to
remove suspended particles; stripping and chemical oxidation to reduce
objectionable taste, odor, or color; and precipitation, softening, pH con-
trol, or other operations designed to produce safe and aesthetically ac-
ceptable finished water from a raw water source, reliably and cost effectively.
More than 1.2 million tons of about 60 bulk chemicals were used for
potable water treatment in the United States in 1981; chemicals used for
disinfection and oxidation amounted to about 42% of that total (Rehwoldt,
19821.
The biocidal efficacy of a chemical or physical disinfectant can depend
on the method of application as well as the methods and staging of other
treatment practices. Thorough mixing is important to ensure uniform dis-
persal and exposure of pathogens to the disinfectant. Pretreatment is often
important to minimize solid particles and aggregates that would shield
pathogens from the disinfectant. If the disinfectant is chemical, pretreat-
ment such as sedimentation of suspended matter, coagulation with alum,
or filtration may also be needed to reduce potential reactants that would,
in effect, consume a disinfectant, thereby reducing the biocidal efficacy
of a given dosage.
Distribution
A drinking water distribution system is more than a means of trans-
porting finished water to the tap. It also acts as a storage system and a
potential source of inorganic, organic, and biological contamination that
must be considered in the design and operation of a potable water supply
system. The distribution system imposes a requirement that adequate post-
disinfection residuals continue biocidal activity.
CHLORINATION
Chlorination has been the predominant method of drinking water dis-
infection in the United States for more than 70 years. When concerns
about the formation of trihalomethanes and other halogenated hydrocarbon
by-products began to stimulate the reexamination of chlorination practices
OCR for page 7
Disinfection Methods and Efficacy 7
in the early 1970s, chlorine was being used to disinfect about 95% of the
potable water supplied in the United States (Morris, 19711.
Chlorine, a strong oxidizing and disinfecting agent, is an effective
microbiocide against most waterborne pathogens. It is inexpensive and
relatively convenient to produce, store, transport, and use. Nonetheless,
because it is a gas at room temperature it can present safety problems,
especially during transportation and storage. Its high solubility in water
makes it easy to apply in controlled amounts either as chlorine gas, which
readily dissolves in water at room temperature, or as a salt of hypochlorite,
which is formed by the reaction of chlorine and water as follows:
C12 + H2O =
HOCl + H+ + Cl
HOCl + H2O = H+ + OCl
During chlorination, the relative concentrations of the hypochlorous
acid (HOC1) and hypochlorite ions (OCl-), together termed "free chlor-
ine," are determined mainly by measurement of pH. HOCl, a more ef-
fective biocide than OCl-, dissociates into OCl- between a pH of 7.0
and 8.0, the range in which most potable water undergoes treatment
(Figure 2-24.
Inorganic and organic molecules, suspended particles, and microbiota
in raw water produce what is termed "chlorine demand," because they
react with and consume free chlorine, requiring a higher dose of additional
chlorine for equivalent biocidal activity. Addition of chlorine beyond the
chlorine-demand "breakpoint" produces a free-chlorine residual, which,
together with time of exposure, forms the practical basis for determining
required amounts of disinfectant.
Sedimentation, coagulation, filtration, aeration, or any other practices
that remove chlorine-demanding substances before chlorination reduce the
amount of chlorine required to produce equivalent disinfection. Such prac-
tices may also remove humic acids and other organic precursors before
chlorination, thereby reducing the formation of trihalomethanes and other
by-products of concern (NRC, 19771.
Postdisinfection biocidal activity persists in a chlorinated drinking water
distribution system. This residual activity, an important advantage of chlo-
rination, is primarily due to the reaction of hypochlorous acid with am-
monia and amines in raw water to form chloramines, which are less
effective as biocides but persist longer than chlorine.
The mechanism of chlorine's highly effective biocidal action against
indicator bacteria appears to involve alteration of cell membrane perme-
ability and disruption of enzymatic reactions within the cell (NRC,
1980a). The relative efficacies of HOC1, OCl -, and chloramines against
bacteria, viruses, and protozoan cysts, compared with those of several
OCR for page 8
~ DRINKING WATER AND HEALTH
boor ~
80
60
40
20
o
O
- 20°C
O°C
1 1 1 1 \41
4 5 6 7 8 9 10 11
pH
20
40 _
-
-
o
60
80
100
FIGURE 2-2 Effect of pH on quantities of hypochlorous acid (HOC1)
and hypochlonte ion (OC1-) that are present in water (NRC, 1980a).
alternative disinfectants (see next section), are summarized in Tables
2-1 and 2-2.
ALTERNATIVE METHODS
The suitability of any method for drinking water disinfection can be
evaluated on the basis of its efficacy against waterborne pathogens, the
accuracy with which it can be monitored and controlled, its ability to
provide the necessary residual biocidal activity in the distribution system,
the aesthetic quality of the treated water, the applicability of the technology
to large-scale operations, and the formation of toxic by-products (NRC,
1977, 1980a,b). Cost may also be a factor, although the costs of several
alternative disinfection methods compared by Clark (1981) did not vary
by more than threefold to fourfold. Also relevant are the comparative
hazards of production, use, transport, disposal, and cleanup.
Restricting itself to toxicological and technological criteria, the Safe
Drinking Water Committee has previously (NRC, 1980a) judged three of
OCR for page 9
Disinfection Methods and Efficacy 9
the many possible alternatives to chlorine to be suitable for primary or
secondary drinking water disinfection: ozone, chlorine dioxide, and chlor-
amines (Table 2-31.
Ozone
Ozone (03) is a strong oxidizing gas that reacts rapidly with most organic
(and many inorganic) molecules. Its short half-life in water, approximately
10 to 30 minutes in practical treatment applications, requires ozone to be
generated on-site for use as a disinfectant. Ozone does not produce a
disinfecting residual, so a second disinfectant must usually be added to
the treated water to furnish the necessary protection in the distribution
system.
Ozone is used as the primary disinfectant in many drinking water treat-
ment plants, mostly in Europe and Canada. Small-scale applications have
been limited in the past owing to maintenance and repair requirements for
a reliable power source; but the large-scale technology is well established,
and both the reliability and efficiency of ozone technology are improving
rapidly. A typical ozone disinfection system consists of modular solid-
state generators, air predrying equipment (necessary to produce ozone
efficiently), and contactors designed to produce good mixing with the
water being treated.
Ozone is an efficient biocide that appears to attack the double bonds
of fatty acids in bacterial cell walls and the protein capsid of viruses (NRC,
1980a). Its overall efficacy against waterborne pathogens is summarized
in Table 2-1.
Chlorine Dioxide
Chlorine dioxide (C1O2) is used mainly as an industrial bleaching agent
for wood pulp, textiles, flour, fats, oils, and waxes, but it has been widely
used at drinking water treatment plants for taste, odor, and algal control;
iron and manganese removal; and (mainly in Europe) disinfection. Since
C1O2 is unstable; sensitive to temperature, pressure, and light; and ex-
plosive in air at concentrations of about 4% or more, it is usually generated
and used on-site to avoid problems of bulk storage and distribution.
C1O2 is highly effective as a biocide against bacteria and viruses under
the temperature, pH, and turbidity conditions of drinking water treatment
(Table 2-11.
ChIoramination
Although chloramines are less effective than free chlorine as biocides
(Table 2-1), they are more persistent and do not react to form trihalo
OCR for page 10
10
_
~O D ~
~ ~ 0 Ct o ~
. ~ pt · s_ ~ ~0 o
~ ~ ~ ~ ~O Ct
C: -
Ct
3
~:
._
~:
s~
`~,o.
C)
U.
V,
C~
.
;^
C~
C~
~o
o
C~
U.
.
o
o
._
C~
._
-
._
cn
C~
o
o
o
~C
m ~ ~=
~:~ ~
Ct
.=
C)
C)
Ct
P:)
-
._
-
o
C~
~_
C~
+ +
+
+ +
+ +
+
+
+
+ +
+ +
+ + +
+ +
1
+
+ ~
+ z
+ +
+ +
+ +
+ +
+ +
+ +
+
+
~, 5, ~ 9
C~
o o o _
C .: ~ ~ ·- ~ o
OCR for page 11
11
D ,_
- C~:
O
~s
D
O ~
+ + +
+ +
+ +
~C~
+ + + +
+ + +
+ + +
+ +
+ + + +
+ + + +
+ + +
+ + +
~o
~c) C~
Ct ~O -
~ ~V C<' ~
3~ ~: ~
° ~c, ~<,, ~ 3
0 ,,, ~ . ~,= _
~ ~c~ ~ t4 . ::
~ ~ ~o
Z
u~
.O _. ~ O
~ ~ 0 ~c~
0 ~ 0 . _
< < E O
~o m °
o
-
o
tl
. ~
._
.>
Ct
-
._
o
._
D
30
_._
v~
_~
+~
._
c~
. ~. _
.~
._0
CtD
C~
. _C~
03
._
~3
e~
0
+
-
._
c'
o
._
o
+
+
._
;>
._
. ~
-
_ e~
_ ~
1 ·-
~ 0
_ . _
-
~ x
0 ~
-
+
+ ct
Z c'
+ ~
ce
~o C,'
ce . ~ c~
Ct Ct
~ ~ ~r
Ct
C~
o
o
e~
Ct
o
C~
o
=
s~
C~
~0
~
e,~
. O ~:
.^ 00 ~ ~
;^ ~ O c:
._ ~ _ _
~ Ct O
._ ~ ~
~ O ~
Ct ~ O
Ct ~; C)
·~ D t
O C~
c) 3 ~
O ~ O
c: ~ ~:
o Ct ~
~ ~ 3
~ ~ ce
.'
_
e, D ~
s::
~ ~ V V
=: )_
~ ·-
3 ~ ,.~
·= 50
~ ~ Ce s
=.= O.
C) L., t-
~ m Li,~
OCR for page 12
12
a,
so
1
Ct
C::
._
Cal
Cal
._
Cal
so
o
o
so
C)
._
o
o
o
._
Cd
.>
C)
._
U)
4-
C)
._
C~
._
o
Ct
C~
L~
s~
Ct
C~
C~
m ~
;^
C~
C~
.
O
~ .
Ct
_
Ct
_ ~ ~
ca
.
o
.
O ~
Ct
_
O -o
.~
.
C~
~ S
:=
O _
X ~
0 00
~_
a~
o
00
1
O ~ C~ O
O O O ~ O
- ~ _ O O O _ _
-
O ~ O ~ O
~ ~ _ C~
O O O V~ O O O O
. . . . . . . .
~ ~ ~ ° ~ ~ ~ ~
o
~C~
o
0 0 0 00
0 ~ 0
0
U~ U~
C ~C~_ c~ _
0 00 0 ~
. . . . .
~ C~ ~ 0 oo oo oo oo 0
0 ~ 0 0 ~ ~ ~ ~ ~U~
. . . . . . . . . .
0 0 0 0 0 0 0 0 0 ~U~
C~
1 1
_ ~ O ~ ~ 0 0
_ _ c~ _ c~ c-~ c-
0 0 0 0 U~ V~
. . . .. .
°
C)
Ct 0
ca ~ ._
0 ~0
~·c ._
0 0 ~
~ 0 °
;^ ~ ~
:r: ~ 0 ~
3
o
"S:
· C.)
Ct -
~ Ct
Ct
s~ ~
C) C)
~ -
o _
U,
o ._
_ ~
D ·-
~ 3
C')
5~ ._
O r
_
C~
-
_ _
Ct
Ct
_ ~
0c ~
·c O
~ C~
S
C)
S~ ;>
3
~o
. ~
C)
Ct
3
t4
. ~ Ct
~ .~
~o 3
o
~o ~
o
- ~ C)
o 3
::
e~
, -
3 ~
Ct
Ct
._
C.)
X
.- C)
'~ o °
~k ~d
o
o
~ ._
C) ~ .
C.)
3 .
't 3 °=
~ C) ;,-
- -
~ ._
~ . ~ ~
,_ V
.- E- C~
V~ ~ ~
<,, _ C~ _
o ~ U ~o o
r~ ~ t_ ON ~
._
~ o
C) -,
._ C~
~ ~ °
._ ~ ~
~ o °
"o ~s
m ~
~:
.s
Ct
- o
C)
._
.=
C)
-
-
C~
-
o
U,
._
-
._
-
. ~
- _
_ ~
. ~
~ .=
^ C~D
_% ._
Ct
0 ~
~ 0
_ ~
~ O
~ . _
Z ~
C)
o o
Lt ~
V)
C)
Ct
OCR for page 13
Disinfection Methods and Efficacy 13
TABLE 2-3 Status of Possible Methods of Drinking Water Disinfectiona
Suitability Suitability for
Disinfection as Inactivating Drinking Water
Agent Agent Limitations Disinfectionb
Ozone
Chlorine Yes Efficacy decreases with Yes
increasing pH;
affected by ammonia
or organic nitrogen
Yes On-site generation Yes
required; no residual;
other disinfectant
needed for residual
Chlorine dioxide Yes On-site generation Yes
required; interim
MCL 1.0 mg/liter
Iodine Yes Biocidal activity No
sensitive to pH
Bromine Yes Lack of technological No
experience; activity
may be pH sensitive
Chloramines No Mediocre bactericide; Not
poor virucide
Ferrate Yes Moderate bactericide; No
good virucide;
residual unstable;
lack of technological
experience
High pH conditions No Poor biocide No
Hydrogen peroxide No Poor biocide No
Ionizing radiation Yes Lack of technological No
experience
Potassium permanganate No Poor biocide No
Silver No Poor biocide; MCL No
0.05 mg/liter
UV light Yes Adequate biocide; no No
residual; use limited
by equipment
maintenance
considerations
aData from NRC (1980a), p. 1 18.
bThis evaluation relates solely to the suitability for controlling infectious disease transmission.
See Conclusions.
CChloramines may have use as a secondary disinfectant in the distribution system in view of
their persistence.
methanes. Concerns about halogenated by-products of chlorination, and
the maximum contaminant level (MCL) of 0.10 mg of total trihalometh-
anes per liter set by the Environmental Protection Agency under the Safe
Drinking Water Act (EPA 1979, 1980), have caused treatment facilities
in several states to increase or switch to chloramination (Hack, 19851.
OCR for page 14
14 DRINKING WATER AND HEALTH
Kansas now requires the use of ammonia to convert all the free-chlorine
residual to chloramines following 30 minutes of chlorination. The Met-
ropolitan Water District of Southern California has changed from chlo-
r~nation to chloramination for distribution system disinfection. In contrast,
several states continue to prohibit chloramination, as Kansas formerly did.
WATERBORNE PATHOGENS
Outbreaks of waterborne disease associated with drinking water from
1978 to 1984 are shown in Table 2-4. During this time, 261 outbreaks
were observed, with almost 72,000 cases. The average annual number of
outbreaks corresponded to 37, with more than lO,OOO cases.
The etiology of disease found in drinking water has changed dramati-
cally since the early l900s. While the early diseases associated with
drinking water were those with a bacterial etiology, the more recent out-
breaks appear to be dominated by gastrointestinal illness associated with
viruses and protozoa. The agents associated with the waterborne outbreaks
for 1984 are shown in Table 2-5. The data in the table are dominated by
acute gastrointestinal illness, which was responsible for nine outbreaks,
with 426 cases. Despite the fact that no agent was identifiable in these
episodes of waterborne illness, a significant percentage of these outbreaks
is believed to be caused by Norwalk or Norwalk-like virus (Kaplan et al.,
1982; Kappus et al., 1982; Taylor et al., 1981; Wilson et al., 19821. In
1983, three outbreaks with 164 cases were due to hepatitis A virus (CDC,
1984), while in 1984 only one outbreak with seven cases was reported
TABLE 2-4 Disease Associated with Drinking Water, 1978-1984a
Number of Outbreaks According to Water Source
Non- Number of
Year Community community Private Total Cases
1978 10 18 4 32 11,435
1979 23 14 4 41 9,720
1980 23 22 5 50 20,008
1981 14 16 2 32 4,430
1982 22 12 6 40 3,456
1983 29 6 5 40 20,905
1984 13 4 9 26 1,755
TOTAL 134 92 35 261 71,709
Average 37 10,244
aData from CDC (1985).
OCR for page 16
i6 DRINKING WATER AND HEALTH
TABLE 2-6 C t Products for 99% Inactivation of Various
Microorganisms by Free Chlorine at 5°C, pH 6.0
Chlorine
ConcentrationTime
Microorganism (mg/liter)(min) C t Reference
-
E. cold 0.10.4 0.4 Scarpino et al. (1972)
Poliovirus 1 1.01.7 1.7 Scarpino et al. (1972)
E. histolyticaa 5.018 90 Snow (1956)
cysts
G. Iambliab 1.050 50 Jarroll et al. (1981)
cysts
2.040 80 Ja~Toll et al. (1981)
4.020 80 Ja~Toll et al. (1981)
8.09 72 Ja~Toll et al. (1981)
G. IambliaC 2.530 75 Rice et al. (1982)
cysts
G. Iambliab 2.5100 250a Rice et al. (1982)
cysts
G. muris 2.5100 250a Rice et al. (1982)
cysts
aExtrapolated data.
bCysts from asymptomatic carriers.
CCysts from symptomatic earners.
represented by Escherichia colt. C t results for G. Iamblia, based on
cysts from the same source using different chlorine concentrations and
exposure times, are similar. The results also indicate that G. Iamblia from
different sources may vary in resistance and that G. muris cysts are similar
in resistance to G. Iamblia cysts.
Additional data showing the effects of temperature and pH on cyst
inactivation by free chlorine are presented in Table 2-7 (G. Iamblia) and
Table 2-8 (G. muris). For cysts of both species, the general decrease in
inactivation rates at lower temperatures is evident. The decrease in free-
chlorine efficiency with increasing pH is due to the shift from the more
effective hypochlorous acid form to the less effective hypochlorite form.
Table 2-9 presents data on inactivation of G. muris by chloramine. The
results point up the lower disinfection efficiency of chloramine. The dif-
ferences between free- and combined-chlorine efficiency appear to be
greater at higher temperatures.
The literature on mechanisms of inactivation of other microorganisms
by monochloramines is limited. Nusbaum (1952) proposed that the mech-
anism of bactericidal action of monochloramine is similar to that of hy-
pochlorous acid; that is, the chloramine molecules enter the cytoplasm
and interfere with enzymatic reactions. Ingold (1969) suggested that mono
OCR for page 17
17
-
-
go,
_)
. ~
.
o
o
._
as
>
so
Cal
C)
o
m
¢
Cal
C) ~
~ .O
Z O ~
Ct
C)
Cal
~ O
a
.O
u, o
oo ~
TIC
a_
SO
C¢
~ ~ _ ~ ~ _ ~ '_ ~
I °° °° °° °° °° °° °° °° °°
00 ~ as ~ ax
~- - ~ _ _ _
~. . . . . . . . .
_ ~ ~ Ct e~5 ct cut cat ct _
Cal ~ ~ ~ ~ ~ ~ ~ -
____--___
.O g g g ~ g ~ ~ ~ ~
-
00
_ _ _
~ ~ ~ o o ~ ~
~D \0 ~ - ~ ~ ~ ~ O
- - v
v v
o ~ ~
v~ ~ ~ ~o - u~ c~
~ oo - - ~ ~ u~
~ ~ ~ l l l l
~ ~ ~ ~ - - c~
~ o ~
V_ _
V V
o ~ CN ~ oo
_ ~ ~ _ _
1 1 1 1 1 1
~o ~ ~ ~ ~ ~ ~ ~o ~ oo
o o o o o o
. . . . . .
oo oo oo
1 1 1 1 1 1
o o o ~ ~ U~ ~ ~ V)
. . . . . . . . . .
_ ~ ~ C~ ~ ~ _ _ _
\0 ~D ~ oo ~ ~ oo \0 ~ oo
_ _ _
OCR for page 18
18
. ~
Cal
U)
Co
.~
At;
.~
o
o
Cal
._
C)
sol
o
Cat
o
.
oo
m
5)
5
-7 ~
~ O
Ct
C,7
so
._
C)
hi
Cal
~-
~ I_
.s ~
~ O
Cal Cal
~ c: C)
~ ~ . _
O ~
TIC
o
Cal
EM
of Do
cry Ch
is - - ~
AD . . ~
oo - - oo
_ A, ~) _
t_ _ _ ~
·D ~ ~0 ·=
C~
oo
~ ~ ~ CS
-,
oo o0 oo
Ce _ _ _
~ >, ;^ ~
~ ~ ~ ._
._ ~ ,~
~ ~ ~ ~ - ~ ~ ~
O o0 0 0 0 ~ ~ ~D
~ ~ ~ ~ ~ ~ ~ o
~ - ~ ~
-
o
- o oo ~ ~ ~
t-
1 1 1 11 1 1
o crN
oo ~ - r~ ~ u~ ~ oo
c~ - - ~-
-
oo
o (3N o t
- ~ ~ ~
1 1 1 1
~ ~ o ~
~ ~ u~ ~
u ~- ~
~ o ~
. . .
Ko ~ ~
- - -
1 1 1
o cn ~ o
o
- ~ ~ ~
~ - o ~ - ~ - ~
t - t
1 1 1 1 1 1 1
(o
- ~ ~ ~ ~ ~ c~ -
o o o -
. .
- - ) ~ ~ ~ ~ ~ ~
oo
a~
-
~:
o
. -
c~
c)
. -
o
e
~ o
- ~
o ~
.- ~
c~ ~
·= o
~ ~ -
~ D
O ~
_ _
~ O
O
=, ·-
O ~
._ ~
~ ._
O ~
C~ ~
~ _
D Ct
~ O
-O ·-
~ O
~ ~_
· _ E_
C)
;>
._ ~
~ ._
_
C)
_ ._
Ct 0D
O ~
._ _
_4 ·_
O ~
_
^ S
·-
Ct
c:
~ 8
~ ^
-
_ ~
· (t
·o ·m
C~
~o <:
C~
V,
O
·= ~
Ct
C~
C)
'< ~a~
V
OCR for page 19
19
is:
C)
5 go:
(L) ·s
Do o
PA ~
.s
Ct
o
Cal
Cal
Cq
~
c
O Z
._ . .
Cal _
C
X
Z O
I,
~.0
v Son ~~
.
0~
m
o
Cal
~ -0 ~ ~ ~ ~ ~ ~
A_ A_ _ A_ A_ _` ~ ~ of i,, ~ ~ ~
ED ED ~ ~ \0 ~ ~ ~ _- A_ A_ _ _
00 of 00 00 00 00 00 00
at cr ~ cr. ~ ~ ~ ox Go oo oo on oo
________
_____
So ~ ~ S S. $, ~
.= .= .~ ~ .= .= . .= .=
con c) c) D ~ D ID
V V V V V V V V ~ Pt P~ Pt P~
c~ c~ cn u, c~
O O O O O O O O ~ ~ ~ C) ~
ZZZZZZZz>(~>
c~ ~ ~ ~ ~ ~ c~ ~ _ c~ - d'
t~ ~ ~ O O O O O
a~` - c~ ~ a, oo - oo c~ ~ ~- ~
~t ~ ~ ~ - - ~ 00 t- ~ O. ')
_ _ _
O O
~O~- - 00 ~C) C~00 0
ON ~ ~ oO ^
- ) - ) ~ ~ ~_ _
1 1 1 1 1 1 1 1 1 1 1
0 ~ ~ v~ _ cr~ ~ ~ ~ 0 ON O O
- , c~ ~ a~` ~ - ~ ~ oo O c~ 0 - 1
~t ~ ~ - ] - - - 00 ~t ~ O~ ~
_ _ _
.C:~ v.~ ~ `~C~ t- ~ ~) - ~O
ax ~ ~ c~ ~ v ~oo
_ _
1 1 1 1 1 1 1 1 1 1 1
oo ~o ~ ~ ~ oo ~ oo ~ r~ 0
00 ~ C~ C~ \0 ~ ~ ~ O O 00
_ ~ C~ _ _ ~ _ ~ ~ 00
-
-
C ~( ~0 t_ ~ ~
_ C ~- - 00
1 1 1 1 1 1 1 1 1 1 1
U ~- O. - 00 ~ 00 0
________~-)
~In ~n ~ ~
. . . . .
00 ~ ~ ~ 00 ~ 00 ~ 00
O O oo oo oo - ', ~ Ir,
- - - - - - -
oo
-
~o
oo
a~
-
o
.-
e
o c~
. - . -
e~
c)
.
3 ~
~ O
~ _
O ~
_ O
O ~
s~ ~
~ O
~ ._
~ O
oc ^
O ~
;^
._
C~
;>
._
~:
o
3
o
C~
{:q
-
. '
~ o
~ _ C~
~ ~o
. ~ P~
o
e~
~ .
·O V
Ct
o
._
o
. -
._
o~
3
-
._
._
o
._
D
OCR for page 20
20 DRINKING WATER AND HEALTH
chloramine was known to oxidize sulfhydryl groups immediately and
irreversibly. On the other hand, Jacangelo and Olivieri (1985) have shown
that monochloramine reacts rapidly with several amino acids including
cystine. In the presence of excess monochloramine, reactions with other
amino acids may also occur. A less rapid reaction, but still more rapid
than with other amino acids, occurs between monochloramine and aspara-
gine, aspartic acid, histidine, lysine, and tyrosine (Jacangelo and Olivieri,
19851. The inactivation of enzymes that occurs during monochloramine
oxidation is believed to be the lethal event in the killing of bacteria.
Nucleic acids, particularly deoxyribonucleic acid (DNA), react com-
paratively rapidly with monochloramine. The purine and pyrimidine bases
react with monochloramine about 0.6 times as rapidly as the nucleosides
(Jacangelo and Olivieri, 19851. Scission of the nucleic acid polymer, rather
than substitution reactions on the purine or pyrimidine bases, is believed
to be responsible for the inactivation of DNA or ribonucleic acid (RNA).
In a study carried out by Shih and Lederberg (1976), when monochlor-
amine was applied to Bacillus subtilis cells in viva or to the extracted
bacterial DNA, it caused double- and single-strand breaks.
Comparative inactivation of G. muris and other types of microorganisms
by ozone is shown in Table 2-10. The overall resistance pattern is similar
to that for chlorine, with cyst resistance being approximately 1 order of
magnitude higher than that for poliovirus 1 and 2 to 3 orders of magnitude
higher than that for E. colt. The much lower C t products also point up
the much higher efficiency of ozone compared with chlorine.
Inactivation of G. muris cysts by chlorine dioxide has been studied by
one group of researchers (A. J. Rubin, Professor of Civil Engineering,
The Ohio State University, Columbus, Ohio, personal communication,
1986~. The results are shown in Table 2-11. The data indicate that chlorine
dioxide is considerably more effective than free chlorine but not so ef-
fective as ozone for inactivating Giardia cysts.
The use of ultraviolet (UV) radiation for low-maintenance, cost-effec-
tive disinfection in small water supply systems is under active consider-
ation. The results of laboratory studies on the effectiveness of UV radiation
against G. Iamblia cysts (Rice and Hoff, 1981) indicate that at the max-
imum dose used (63,000 ~W-sec/cm2), less than 80% of the cysts were
inactivated, whereas a dose of 3,000 ~W-sec/cm2 inactivated 99.9% of
an exposed E. cold population. This is very significant when one considers
that the maximum designed dose range of many commercially available
UV treatment units is 25,000 to 35,000 ~W-sec/cm2. Other studies in
progress confirm the high resistance of Giardia cysts to UV radiation
(Carlson et al., 19851.
The results of recent studies indicate that, contrary to our general impres-
sions 10 years ago, Giardia cysts can be inactivated by drinking water
OCR for page 21
21
v~
oo
~ ~ - -
oo oo
- -
~:
o
o
c~
;^
.~
~:
cd
-
c~
~ -
o
-
o
- ~
o
.
o
o
~ -
~ -
~:
-
s~
,~o4
c~
-
'e
.
o
-
m
C}
S
C)
C)
-
~.~
D s~
s ~C)
Z O ~
e~
_ _
Ct Ct
_ _
C) ~
O
C~
-
C
C)
:d
oo
-
-
-
o
'_ _ '_ _`
U~ ~ U~
o0 oo oo oo
~ ~ C~
_ _ _ _
~, ~ ~
_ _
Ct Ct
_ _
C) ~
. . .
_ _ _
Ct Ct C¢
_ _ _
C)
C) ~ C~ ~ ~
=: ~ ~ ~: ~:
Ct Ct Ct Ct Ct
~ ~ ;^
Ct Ct Ct Ct Ct
~ ~ ~ ~ ~:
Ct Ct Ct Ct C5
's ~ ~ ~ ~
C5 e~ C~ Ct Ct
C) C) C) C) C~
._ ._ ._ ._ ._
3 3 3 3 3
_ _ _ ~ C - ) ~ ~ - ,
~ ~ o
~ ~ o
O ~D ~ ~ ~
~ ~c~ o o o o
O ~1 1 1 1 1 1
o
~. .. . . . . .
~ o o o - o o o o
s.-
·~
- -o
ts =.-
aO~
~o ~
C)
Ct
a
.
e~
S~
-0 ~
.
00
. . . . .
O O O O
O ~ ~ ~
. . . . .
a~ ~ ~ oo
oo ~1 1 1 1 1
O ~ ~ ~ O ~ ~ O
. . . . . . . .
O O ~
. . . . .
~n O O O 0 0
1 1 1 1 1
O O ~ {~} C~)
O O O O O O °. °.
O O
. . .
~ ~ ~ ~ ~ ~ r~
_ _ ~, Ir, ~ ~) ~)
~ C~
.~5 .3
·~ .S:3 · - ·L,
. . . . .
C: ~ ;3 ~ C3
OCR for page 22
22 DRINKING WATER AND HEALTH
TABLE 2-11 C · t Products for 99% Inactivation of G. muris Cysts by
Chlorine Dioxide
Range
Disin
fectant Number
Temper- Cvncen- of
ature tration Time Mean Expen
(°C) pH (mg/liter) (min) Ct Ct meets Reference
5 7 0.11-5.55 1.3-168 7.2-17.6 11.0 5 Rubin (1986)a
25 7 0.22-1.13 3.3-28.8 3.7-6.2 5.0 5 Rubin (1986)a
25 9 0.16-0.82 2.1-19.2 1.7-3.7 2.8 4 Rubin (1986)a
aA. J. Rubin, Professor of Civil Engineering, The Ohio State University, Columbus, Ohio,
personal communication, 1986.
disinfectants. The order of efficacy of disinfectants conventionally used
for drinking water treatment is ozone > chlorine dioxide > free chlorine
> chloramine. Giardia cysts are among the most resistant pathogens
known, however, and the disinfection step must be conducted rigorously
under well-controlled conditions. This is especially important during pe-
riods when water temperatures are low. Employing additional treatment
processes to remove substantial numbers of cysts before disinfection is
also important in order to decrease reliance on disinfection.
viruses
The majority of tests described in the literature pertaining to inactivation
of human viruses with drinking water disinfectants have been conducted
with human enteroviruses, poliovirus, Coxsackievirus, and echovirus. While
the data collected about these viruses are useful, data on the viruses that
are responsible for the diseases observed in drinking water are even more
important. Culture methods for hepatitis A virus have recently become
available, and several have been reported (Grabow et al., 1983; Peterson
et al., 1983~. Recent information is summarized in Table 2-12 in the light
of other information for the human enteroviruses. The information is
presented as the product of the disinfection concentration times the contact
time necessary for 99% inactivation. The data on the human enteroviruses
were taken from an earlier summary (NRC, 1980a). The C t product
for poliovirus was about 1 to 2 and 10.5 for hypochlorous
acid and hypochlorite ion, respectively. The C t product estimated
from the data reported by Peterson et al. (1983) for 99% inactivation
of hepatitis A virus was about 60 at pH 7 (a mixture of hypochlorous
acid and hypochlorite ion). The C t for 99% inactivation is at best a
crude estimate and was approximated from data presented for the sero
OCR for page 23
Disinfection Methods and Efficacy 23
TABLE 2-12 The Inactivation of Selected Viruses with Chlorine
Disinfectants
Test Temper
Micro- Disin- ature
organism fectant pH (°C)C t Reference
E. cold HOC1 6.0 50.04 NRC (1980a)
OCl- 10.0 50.92 NRC (1980a)
NH2C1 9.0 5175.00 NRC (1980a)
Poliovirus 1 HOC1 6.0 51-2 NRC (1980a)
OC1- 10.0 510.5 NRC (1980a)
NH2C1 9.0 15900.0 NRC (1980a)
Rotovirus HOC1 a a0.25 NRC (1980a)
OC1- a a1.4 NRC (1980a)
NH2C1 a aa
Hepatitis A HOCl 7.0 5Gob Peterson et al. (1983)
HOC1 6.0 a<0.32C Grabow et al. (1983)
OC1- 10.0 a<1.04C Grabow et al. (1983)
NH2C1 a
Norwalk agent HOCl/OCl- 7.4 25a Keswick et al. (1985)
aNot reported.
bC · t estimated from animal infectivity data.
CC t estimated from disinfection curves. Chlorine residual data suggested that the test mixtures
contained significant demand. Concentration used for calculation was the dose reported.
conversion of marmoset monkeys (Saguinus spp. ). Grabow et al. ( 1983)
reported that the infectious hepatitis agent was much more sensitive to
chlorine. Hepatitis A virus was titrated with a multiple-tube dilution
procedure coupled with a radioimmune assay that allowed the deter-
mination of the probable number of viruses during disinfection with
chlorine. The C t product for 99% inactivation of hepatitis A virus
from their graphic presentation was <0.32 for hypochlorous acid at pH
6.0 and <1.04 for hypochlorite ion at pH 10.0. The study reported
comparative data for other microorganisms, and the hepatitis A virus
did not appear to be particularly resistant to chlorine. The conditions
normally specified for the disinfection of drinking water with free chlo-
rine would successfully inactivate hepatitis A virus. The C t products
reported for 99% inactivation of poliovirus by combined chlorine are
considerably higher, and C t products as high as 900 have been re-
ported. No data are available at present on the inactivation of hepatitis
A virus by the combined forms of chlorine. As with other viruses, the
suspected resistance of this agent may be due to the dramatic differences
in the rates of inactivation with free and combined chlorine.
While culture methods are not available for Norwalk agent, limited
information has become available from human volunteer studies. Keswick
et al. (1985) reported that Norwalk agent appeared to be more resistant
OCR for page 24
24 DRINKING WATER AND HEALTH
to chlorine than two strains of rotovirus, one strain of poliovirus, and F2
bacterial virus. Close inspection of the reported data shows that for chlorine
doses of 3.75 to 6.25 mg/liter, the majority of the chlorine was in the
combined form. Free chlorine was observed after 30 minutes in the ro-
tovirus and poliovirus trials, and these viruses were not recovered. How-
ever. after 30 minutes no free chlorine was found in the Norwalk trial,
and only trace quantities of free chlorine were found in the F2 trial. In
each case the viruses were not completely inactivated. The data suggesting
the resistance of Norwalk agent to free chlorine are difficult to interpret
without a clear definition of the nature of the chlorine species present in
the reaction system. The reported resistance may be due to the marked
difference in the vir~cidal activity of free and combined chlorine that has
been reported for other viruses (NRC, 1980a).
REFERENCES
Akin, E. W., J. C. Hoff, and E. C. Lippy. 1982. Waterborne outbreak control: Which
disinfectant? Environ. Health Perspect. 46:7- 12.
Barrett, S. E., M. K. Davis, and M. J. McGuire. 1985. Blending chloraminated and chlor-
inated waters. J. Am. Water Works Assoc. 77(1):50-61.
Carlson, D. A., R. W. Seabloom, F. B. DeWalle, T. F. Wetzler, J. Engeset, R. Butler,
S. Wangsuphuchart, and S. Wang. 1985. Ultraviolet Disinfection of Water for Small
Water Supplies. Doc. No. EPA/600/2-85/092. Water Engineering Research Laboratory,
U. S. Environmental Protection Agency, Cincinnati, Ohio. [125 pp.]
CDC (Centers for Disease Control). 1984. Water-Related Disease Outbreaks. Annual Sum-
mary 1983. Centers for Disease Control, Public Health Service, U.S. Department of
Health and Human Services, Atlanta, Ga. [19 pp.]
CDC (Centers for Disease Control). 1985. Water-Related Disease Outbreaks. Annual Sum-
mary 1984. Centers for Disease Control, Public Health Service, U.S. Department of
Health and Human Services, Atlanta, Ga. [19 pp.]
Clark, R. M. 1981. Evaluating costs and benefits of alternative disinfectants. J. Am. Water
Works Assoc. 73:89-94.
EPA (U.S. Environmental Protection Agency). 1979. National interim primary drinking
water regulations; control of trihalomethanes in drinking water; final rule. Fed. Regist.
44:68624-68707.
EPA (U.S. Environmental Protection Agency). 1980. National interim primary drinking
water regulations; control of trihalomethanes in drinking water; correction. Fed Regist.
45: 15542-15547.
Grabow, W. O. K., V. Gauss-Muller, O. W. Prozesky, and F. Deinhardt. 1983. Inacti-
vation of hepatitis A virus and indicator organisms in water by free chlorine residuals.
Appl. Environ. Microbiol. 46:619-624.
Hack, D. J. 1985. State regulation of chloramination. J. Am. Water Works Assoc. 77(1):46-
49.
Ingold, C. K. 1969. Structure and Mechanism in Organic Chemistry, 2nd ed. Cornell
University Press, Ithaca, N.Y. 1,266 pp.
IRC (International Reference Centre for Community Water Supply and Sanitation). 1984.
IRC at a Glance. IRC, The Hague, The Netherlands. 20 pp.
OCR for page 25
Disinfection Methods and Efficacy 25
Jacangelo, J. G., and V. P. Olivieri. 1985. Aspects of the mode of action of monochlor-
amine. Pp. 575-586 in R. L. Jolley, R. J. Bull, W. P. Davis, S. Katz, M. H. Roberts,
Jr., and V. A. Jacobs, eds. Water Chlorination: Chemistry, Environmental Impact and
Health Effects, Vol. 5. Lewis Publishers, Chelsea, Mich.
Jarroll, E. L., A. K. gingham, and E. A. Meyer. 1981. Effect of chlorine on Giardia
lamblia cyst viability. Appl. Environ. Microbiol. 41:483-487.
Jarroll, E. L., J. C. Hoff, and E. A. Meyer. 1984. Resistance of cysts to disinfection
agents. Pp. 311-328 in S. L. Erlandsen and E. A. Meyer. Giardia and Giardiasis:
Biology, Pathogenesis, and Epidemiology. Plenum, New York
Kaplan, J. E., R. A. Goodman, L. B. Schonberger, E. C. Lippy, and G. W. Gary. 1982.
Gastroenteritis due to Norwalk virus: An outbreak associated with a municipal water
system. J. Infect. Dis. 146:190-197.
Kappus, K. D., J. S. Marks, R. C. Holman, J. K. Bryant, C. Baker, G. W. Gary, and
H. B. Greenberg. 1982. An outbreak of Norwalk gastroenteritis associated with swim-
ming in a pool and secondary person-to-person transmission. Am. J. Epidemiol. 116:834
839.
Katzenelson, E., B. Kletter, and H. I. Shuval. 1974. Inactivation kinetics of viruses and
bacteria in water by use of ozone. J. Am. Water Works Assoc. 66:725-729.
Keswick, B. H., T. K. Satterwhite, P. C. Johnson, H. L. DuPont, S. L. Secor, J. A.
Bitsura, G. W. Gary, and J. C. Hoff. 1985. Inactivation of Norwalk virus in drinking
water by chlorine. Appl. Environ. Microbiol. 50:261-264.
Morris, J. C. 1971. Chlorination and disinfection State of the art. J. Am. Water Works
Assoc. 63:769-774.
NRC (National Research Council). 1977. Drinking Water and Health. National Academy
of Sciences, Washington, D.C. 939 pp.
NRC (National Research Council). 1980a. Drinking Water and Health, Vol. 2. National
Academy Press, Washington, D.C. 393 pp.
NRC (National Research Council). 1980b. Drinking Water and Health, Vol. 3. National
Academy Press, Washington, D.C. 415 pp.
Nusbaum, I. 1952. Sewage chlorination mechanism: A survey of fundamental factors.
Water Sewage Works 99:295-297.
Peterson, D. A., T. R. Hurley, J. C. Hoff, and L. G. Wolfe. 1983. Effect of chlorine
treatment on infectivity of hepatitis A virus. Appl. Environ. Microbiol. 45:223-227.
Rehwoldt, R. 1982. Water chemicals codex. Environ. Sci. Technol. 16:616A-618A.
Rice, E. W., and J. C. Hoff. 1981. Inactivation of Giardia lamblia cysts by ultraviolet
irradiation. Appl. Environ. Microbiol. 42:546-547.
Rice, E. W., J. C. Hoff, and F. W. Schaefer III. 1982. Inactivation of Giardia cysts by
chlorine. Appl. Environ. Microbiol. 43:250-251.
Roy, D., R. S. Englebrecht, and E. S. K. Chian. 1982. Comparative inactivation of six
enteroviruses by ozone. J. Am. Water Works Assoc. 74:660-664.
Scarpino, P. V., G. Berg, S. L. Chang, D. Dahling, and M. Lucas. 1972. A comparative
study of the inactivation of viruses in water by chlorine. Water Res. 6:959-965.
Shih, K. L., and J. Lederberg. 1976. Chloramine mutagenesis in Bacillus subtilis. Science
192:1141- 1143.
Snow, W. B. 1956. Recommended chlorine residuals for military water supplies. J. Am.
Water Works Assoc. 48: 1510- 1514.
Taylor, J. W., G. W. Gary, Jr., and H. B. Greenberg. 1981. Norwalk-related viral gas-
troenteritis due to contaminated drinking water. Am. J. Epidemiol. 114:584-592.
OCR for page 26
26 DRINKING WATER AND HEALTH
WHO (World Health Organization). 1984. The International Drinking Water Supply and
Sanitation Decade: Review of National Baseline Data (as at 31 December 1980). WHO
Offset Publication No. 85. World Health Organization, Geneva. 169 pp.
Wickramanayake, G. B., A. J. Rubin, and O. J. Sproul. 1984. Inactivation of Naegleria
and Giardia cysts in water by ozonation. J. Water Pollut. Control. Fed. 56:983-988.
Wickramanayake, G. B., A. J. Rubin, and O. J. Sproul. 1985. Effects of ozone and storage
temperature on Giardia cysts. J. Am. Water Works Assoc. 77(8):74-77.
Wilson, R., L. J. Anderson, R. C. Holman, G. W. Gary, and H. B. Greenberg. 1982.
Waterborne gastroenteritis due to the Norwalk agent: Clinical and epidemiologic inves-
tigation. Am. J. Public Health 72:72-74.
Representative terms from entire chapter:
free chlorine
