Foundation funded project #4159, “Role of
Bromamine on Disinfection By-Product
Formation and Impact on Application
of Chloramination and Ozonation.” This
ongoing project will evaluate optimized
bromamine formation to minimize bromate
formation during ozonation. The impact of
multiple water quality and process conditions
on bromamine formation and subsequent
bromate formation will be assessed.
Bromate Removal
Prevention of bromate formation is one
technique to comply with DBP regulations.
However, in some circumstances, the
utilities have to deal with bromate removal
after its formation. Several options to
remove bromate after its formation include
ferrous iron (Fe2+) reduction, GAC surface
reduction, UV irradiation, and high energy
electron beam irradiation. Fe2+ reduction,
GAC surface reduction, and decomposition
by UV light irradiation were assessed
for bromate removal after ozonation
in Strategies to Control Bromate and
Bromide. Bench-scale evaluations were
performed with varying spiked levels
of bromate and subsequent pilot tests
were performed for all bromate removal
techniques. While bench-scale results with
Fe2+ were encouraging, pilot tests showed
premature turbidity breakthrough, a result
rectified by simultaneous addition of both
Fe2+ and ferric iron (Fe3+) salts. While both
lab- and pilot-scale results for GAC were
encouraging, the pilot tests were not run
long enough to assess the effects of biofilm
development on GAC. Medium-pressure
UV light irradiation proved to be effective
in bromate decomposition at very high
irradiation doses.
The biological reduction of bromate
using biological active carbon (BAC)
was evaluated in the report, Removal of
Bromate and Perchlorate in Conventional
Ozone/GAC Systems (2001, order #90836/
project #2535). This research found that
biological bromate reduction can be
achieved in BAC filters. However the mass
of bromate removed in the filters can be
affected by concentrations of dissolved
oxygen (DO), nitrate, pH, type of influent
water, and influent bromate concentration.
Filter history can also greatly affect the
subsequent mass of bromate removed in
a BAC filter. Increasing the influent DO
and nitrate concentrations to the BAC
filters decreased bromate removal, but an
increased sulfate concentration did not
have much effect on bromate removal.
Depending on the empty bed contact
time, an increased influent bromate
concentration could cause an increase
in the mass concentration of bromate
removed. Additionally, bromate removal
increased as the influent pH to the BAC
filters decreased to near-neutral values.
Chlorite (ClO2-) and Chlorate (ClO3-)
Chlorine dioxide (ClO2) has been used for
drinking water treatment in the United
States since the 1960s. It was primary used
for preoxidation of NOM, removal of iron
and manganese, taste and odor control,
color removal, algal growth prevention,
and as an alternative to chlorinated
disinfection practices. Due to the discovery
of chlorinated DBPs in the 1970s, various
regulatory changes (e.g. Stage 2 DBPR,
LT2ESWTR), and the prevalence of
chlorine resistant organisms, ClO2 has seen
increased popularity. The current number
of WTPs using ClO2 for disinfection may
range from 500– 1,200. However, the actual
number of plants is difficult to estimate
because some plants may only use ClO2
seasonally or intermittently.
The use of ClO2 within the disinfectant
strategy has the potential to decrease the
concentration of regulated DBPs (e.g.,
