Civil Engineering Reference
In-Depth Information
60 mg / L, and thyroid tumors and peritoneal mesothelioma were detected at doses
as low as 250 mg / L. EPA has classified bromate as a probable human carcinogen
(Group B).
Bromine
Formation and Occurrence
Bromine (Br
2
) is rarely used in drinking water treat-
ment, but has been applied on a limited basis for swimming pools, cooling towers,
and industrial water applications. Bromine is a dark, brownish-red heavy liquid that
emits a sharp, penetrating and suffocating odor at room temperature. Bromine may be
fed to water in the form of liquid bromine or as bromine chloride gas.
In water at neutral pH, the predominant form of bromine is hypobromous acid
(HOBr). Above pH 8.7 and at 25
C, the hypobromite ion (OBr
) is the major form of
bromine. At lower pH values (below 6), Br
2
,Br
3
, bromine chloride, and other halide
complexes form. Bromine and bromine chloride react with basic nitrogen compounds
to from bromamines.
Health Effects
Most health effects data is on bromide salts because of their phar-
maceutical use. Bromide occurs normally in blood at a range of 1.5 to 50 mg / L.
Sedation occurs at a plasma concentration of about 960 mg / L, corresponding to a
maintenance dose of 17 mg / kg-day
1
. Gastrointestinal disturbances can occur at high
doses. No data have been developed on the mutagencity, carcinogenicity, or terato-
genicity of bromine.
3
Chloramines
Formation and Occurrence
Chloramines are formed by the reaction of chlorine
with inorganic ammonia compounds. The predominant form is usually monochlor-
amine, although dichloramine, trichloramine, and nitrogen trichloride may also be
present. Chloramines are effective at bacterial inactivation but do not react extensively
with organic material to form halogenated by-products of concern. As a consequence,
chloramines are widely used as a secondary disinfectant, and less frequently as the
primary disinfectant.
Health Effects
In humans, observed health effects associated with monochloramine
in drinking water have been limited to hemodialysis patients. Chloramines in dialysis
baths cause oxidation of hemoglobin to methemoglobin and denaturation of hemoglo-
bin. Tests conducted on healthy human volunteers to evaluate the effects of mono-
chloramine in drinking water at doses up to 24 mg / L (short term) and 5 mg / L (for
12 weeks) showed no effects.
3
Results on mutagenicity of chloramines are inconclu-
sive. The NAS has determined that there are not sufficient data to determine limits for
humans for either acute or chronic exposure.
Chlorine
Formation and Occurrence
In the gaseous state, chlorine is greenish-yellow and
toxic. Chlorine may also be fed in the hypochlorite form and can occur as an impurity
in the generation of chlorine dioxide. In water, chlorine reacts to form hypochlorous
and hydrochloric acids. The hypochlorous acid then dissociates into hydrogen and
hypochlorite ions. The distribution of chlorine forms is pH dependent—hypochlorous
