Four HANs, (trichloroacetonitrile
[TCAN], DCAN, bromoacetonitrile
[BAN], dibromoacetonitrile [DBAN], and
cyanogen chloride [CNCl]) were among
the unregulated DBPs surveyed in the
Information Collection Rule (ICR). In
Information Collection Rule Data Analysis
(2003, order #90947/project #2799), the
survey data showed that CNCl and HANs
formation were higher in chloraminated
surface water than in groundwater
systems. The ICR evaluated the speciation
of HANs and the effect of bromide on
their formation and showed that, when
compared to THMs and HAAs, the amount
of bromine incorporation in HANs was
much higher than both classes. In a
comparison of formation and speciation
of HANs versus THMs, the percentage
increase in HANs resulting from increased
bromide concentrations was greater than
that for THMs. Bromine-substituted HANs
constituted more than 30% of the total
HANs produced. As expected because
trihaloacetonitriles are known to be unstable,
all TCAN levels were below the minimum
reporting levels (MRLs).
Halonitromethanes are yet another type
of N-DBP and similar to the HAAs, there
are nine halonitromethanes (HNMs).
Trichloronitromethane (also known as
chloropicrin or TCNM) was one of the
unregulated DBPs surveyed in the ICR.
“By-Products of Potential Concern in
Drinking Water Treatment” discusses
the formation of chloropicrin with chlorine,
chloramine, chlorine dioxide, and ozone
in the presence of nitrite. Chlorination
of phenols in the presence of nitrite can
form nitrophenols, which are chloropicrin
precursors. Research has shown that
pre-ozonation can increase the formation
of chloropicrin or other HNMs upon
post-chlorination.
Similar results were obtained in the ongoing
project #4063, “Exploring Formation and
Control of Emerging DBPs in Treatment
Facilities: Halonitromethanes and Iodo-trihalomethanes,” which investigated
the formation and speciation of HNMs
during drinking water treatment. The
study investigated the effect of several
disinfection processes and combinations
on the formation of HNMs. Results showed
that HNM formation was greatest from
ozonation-chlorination, confirming
previous results found in Occurrence and
Formation of Nitrogenous Disinfection
By-Products. Comparatively, other
disinfection strategies formed HNMs in
the order of ozonation-chlorination >>
chlorination ≥ ozonation-chloramination >>
chloramination. This is in agreement with
the previous observations that ozonation
significantly enhanced TCNM formation.
Chloramination after ozonation or
chloramination alone significantly reduced
HNM formation.
Project #4063 also examined the formation
and speciation of HNMs in wastewater
treatment plant effluents. Similar results
to those for drinking water treatment were
obtained. HNM formation was greatly
reduced by applying monochloramine,
especially after ozonation. However, when
formation potential tests were used to
compare HNM yields from treated drinking
water and treated wastewater, the results
showed that HNM yields were higher
in the wastewater effluents than in the
treated drinking water. This indicated that
HNM precursors in the treated wastewater
are significantly more reactive than the
hydrophilic NOM in treated drinking water.
The project also found that the presence
of bromide and nitrite in water increased
HNM formation. Monochloramination
alone did not form any measurable
