|
Items in cart [0] |
Questions? Call 888-624-8373 |
| 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 2
Description of ache Codex
It will be apparent that the body of the Codex is a
series of individual monographs, each dealing with a
specific compound. Each such monograph contains the
following information:
Chemical name--alternative acceptable names
Chemical abstract service number
Chemical formula and formula weight
Physical properties
a. Function
b. Use range
Purity requirements
Bulk sampling procedures
Analytical procedures
a. Sample preparation--special procedures are
noted where appropriate. In cases where the
chemical added is not soluble in water, the
analytical procedures apply to a leachate of
that material as obtained under the conditions
described.
Sample analysis--techniques are given either
as citations of existing recognized procedures
or as procedures developed specifically for
the monograph.
Purity Requirements The committee recognizes that the
assignment of purity requirements depends on the toxicity
of the contaminant and the use patterns of the additive.
m e interpretation of toxicological data is at times con-
troversial and depends on an evolving science. However,
the toxicological data base for water impurities is im
proving steadily.
2
OCR for page 3
3
In arriving at its recommended contaminant limits, the
committee met with the Environmental Protection Agency
(EPA) to arrive at a list of priority chemicals--those
that are used in largest quantities in the public water
supply (Table 1). m is list was then categorized accord-
ing to use pattern, i.e., those used in (a) coagulation
and flocculation; (b) softening, precipitation, and pH
control; (c) disinfection and oxidation; and (d) mis-
cellaneous treatment applications. In drafting the
monographs in each category, a subgroup of the committee
reviewed current data on known impurities in the chem-
icals, grade of manufactured products, use patterns, and
other variables.
The committee also developed a list of impurities to
be considered. m e list was identical to the regulated
inorganic impurities specified by the National Interim
Drinking Water Regulations developed in response to the
Safe Drinking Water Act of 1974 (Table 2).~ This list
was subsequently modified to include those substances for
which there is evidence of occurrence as contaminants in
water treatment chemicals. The toxicology subgroup of
the committee supplied toxicological data on these sub-
TABLE 1 Water Treatment Chemicals Included in this Codex
Activated alumina
Aluminum sulfate
Ammonia
Ammonium hydroxide
Bentonite clay
Calcium hydroxide
Calcium hypochlorite
Calcium oxide
Carbon, activated,
granular, and powder
Carbon dioxide
Chlorine
Ferric chloride
Ferric sulfate
Ferrous sulfate
Fluosilicic acid
Potasium permanganate
Sodium aluminate
Sodium bicarbonate
Sodium calcium magnesium
polyphosphate, glassy
Sodium carbonate
Sodium chlorite
Sodium fluoride
Sodium hydroxide
Sodium metabisulfite
Sodium polyphosphate, glassy
Sodium silicate
Sodium silicofluoride
Sodium tripolyphosphate
Sodium zinc polyphosphate,
glassy
Sodium zinc potassium
polyphosphate, glassy
Sulfur dioxide
Sulfuric acid
Tetrasodium pyrophosphate
OCR for page 4
4
to ~
to . -
~-
to ~
us · -
~ -
10
be
p
In
o
-
By
-
c)
o
In
:>
-
~u
w
ID
EN
..
to
~ to
·~'
·~'
By
In
a)
o
o
oB
x
-
01
10
to · -
u~ ~
to . -
·~.
Ad ~
By ~
'
;
By ~
~4
::
It)
In
Q
:'
VO
C) o o US
~ ~ o
£
~;
C) o o cr'
H ~ O
£ CD
C.) o o o
U~ o
~ o
C: o o
o o
o
a;
r~
O o o
H O O
U~ O
o
C) O O O
H O O O
O O ~
ti: ' '
~ O
C) o
H O
O
Z '
v EE e
· - 0
~- -
U,
54 ~ ~ ~
~n C) C)
O I
~ 1
1
1
o
o
l
ll
!
1
l
1
o o
U~
o o ~ o U, o o
o
o
U~
o o ~ o o o o
U, o ~ U~ o
o
o
o o ~ o o o o
o o o ~ o o
o
o
o o o o o o
o o ~ o o o
u~ ~n 0 ~ u~
o
o
o o o o o o o
0 0 ~r 0 0 0 0
o o o ~ o o
o
o
C~
o ~ o oo
o ~ o o o
o ~ o ~ o
~.
U~ ~ U, o
o
o
~1 .Q1 ~ ~1
U) JJ
1 o to
1 .
o
Q
v
~a
x
s
a,
-
o
O
Q) ~
s
~:
o o o
o o o
o o o
~ ~ o
tQ
U~ o
o o Q
· ~
~ o oo
_
o ~ V ~ ·^
i'4
· - ~ ~ ~
Z ~ U] U]
U]
s
o
s
._'
E~
~a
.,,
C)
e
E~
3 ~
~ :'
o U]
:,
,'
v
~ o
U'
z
o
a)
~ Q
V
~ - -
V
U <:
~1 Ql
OCR for page 5
5
stances, including information on possible genotoxic
effects.
Next, a suggested no-adverse-response level (SNARL) 2
was calculated for a potential contaminant. Irrespective
of known aenotoxic itv . a SNARL mav be calculated f rem
existing data such as threshold limit value (TLV), which
is available from a number of sources, and other para-
meters, including average body weight, intake, and expo-
sure. In most cases, the calculated SNARL value differed
from the TLV or the maximum contaminant level (MCL) found
in the National Interim Drinking Water Regulations
(NIDWR).3
In general, the committee felt it would be appropriate
to utilize the MCL in calculating the allowable contami-
nant level contributed by an impurity in a water treatment
chemical, unless there was no current MCL for that impur-
ity or where there was new information concerning either
the toxicity of the contaminant or the current status of
the MCL.
In the case of lead, recent toxicological data are
available that led the committee to recommend to the EPA
that a lower MCL should be considered. However, the
committee did not feel it consistent to adopt a smaller
number in its calculations at this time.
A SNARL or MCL was thus converted to a recommended
maximum impurity content (RMIC) in the additive by the
following equation:
RMIC =
=
SNARL or MCL
MD x SF
SNARL or MCL (mg/liter) x 106 mg/kg
l-
MD (mg/liter) x SF
Maximum dosage (MD) for the water treatment chemical
was based upon maximum patterns known by the committee to
be representative of water treatment practice.
The safety factor (SF) used in the calculation of the
RMIC was 10, reflecting the view of the committee that no
more than 10% of a given SNARL or MCL value should be
contributed by a given impurity in a water treatment
chemical. Some may argue for a higher safety factor, but
10 was chosen by the committee as reasonable in view of
other uncertainties and approximations relating to the
fate of impurities introduced during treatment.
A sample calculation of a RMIC is as follows:
OCR for page 6
6
Contaminant (Hg):
Water Treatment Additive
MCL 0.002 mg/liter
:
Maximum Dose (MD)
Safety Factor
500 mg/liter
10
RMIC = 0~002 me Hg/liter x 1o6 mg/kg
500 mg Additive/liter x 10
RMIC = 0.4 mg Hg/kg Additive
Table 2 contains RMIC values for impurities of concern at
selected additive dose levels reported to one significant
figure. RMIC values are also contained in the individual
monographs and should be compared to impurity concentra-
tions obtained by using the sample preparation described
in the monograph. m at is, the RMIC values represent
maximum recommended impurity content and as such can be
used as guidelines to the industry. The user is advised
that, if actual dosages applied exceed those upon which
the monograph is based, appropriate RMIC value should be
extrapolated from Table 2.
The committee is aware that for some direct additives
analyses of generally available grades show the presence
of impurities at levels well below those that would be
calculated as a RMIC. In such cases, RMIC values are not
calculated, and the purity requirements are derived from
those analyses.
If cases are found in which a contaminant may create
additional health concern because of its radioactivity,
RMIC values shall be calculated in accordance with radia-
tion limits that appear in the Code of Federal Regula-
tions.~
The RMIC levels are based upon information available
to the committee. It is obviously impossible to recommend
maximum impurities content levels for all possible unusual
or unexpected impurities, the presence of which would de-
pend upon method of manufacture and quality of raw mater-
ial used. If other than recognized methods of manufacture
or if unusual raw materials are used, the user should re-
quire appropriate certification of purity from the vendor
or manufacturer to demonstrate the water treatment chemi-
cal is suitable for its application in the preparation of
potable water. Material regenerated or reclaimed at the
plant site or point of use must also meet Codex specifi-
cations.
OCR for page 7
7
Genotoxic Effects The genotoxic potential of water treat-
ment chemicals impurities was evaluated on a case by case
basis. Appropriate data bases were investigated and pup
fished risk assessments considered.
Epigenetic Effects Evidence for epigenetic effects was
considered where appropriate. However, as in the case of
carbon tetrachloride, sufficient data were not available
to use epigenetic mechanisms as sole basis for determining
minimum contaminant levels.
Analytical Methods Preferred sampling, sample prepara-
tion, and analytical methods for the determination of
impurities are cited. It is recognized that a number of
water treatment chemicals require special sample prepar-
ation and/or analysis due to matrix or other effects.
For such chemicals the recommended special procedures are
included in the Codex.
Methods that are cited or appear in the Codex should
be considered the preferred analytical procedures; alter-
native methods may be used if they can be shown to be
equivalent.
Revision It is expected that the Codex will be reviewed
continuously and annual supplements issued. The supple-
ments may contain additional chemicals and revisions of
the monographs contained in the present Codex, as well as
revision of analytical procedures.
LITERATURE CITED
1. Code of Federal Regulations, 40:141, 1981.
2. Safe Drinking Water Committee. 1980. Drinking Water
and Health. National Academy of Sciences, Washington,
D.C. 70 pp.
3. Environmental Protection Agency. 1976. National
Drinking Water Regulations. EPA-570/9-76-003.
Environmental Protection Agency, Washington, D.C.
4. American Water Works Association. 1981. Standard for
Ammonium Sulfate. AWWA B302-81. American Water Works
Association, Denver, Colorado.
OCR for page 8
Representative terms from entire chapter:
drinking water
