to identify improving our understanding of
chloramine use and decay as a program goal
(see sidebar).
Since the mid-1980s, the Water Research
Foundation has funded more than 60
research projects that examine chloramine-related issues, such as making the switch to
chloramines, nitrification events, formation
of disinfection by-products, formation
of nitrogenous disinfection by-products,
and lead and copper release as related to
chloramine use. What follows is a summary
of this work as well as information on
work expected to be completed under the
Strategic Initiative.
Switching to Chloramines
Although the Economic Analysis for the
Stage 2 D/DBP Rule produced by the
USEPA estimated that more than 50 percent
of the surface water systems would use
chloramines as a secondary disinfectant,
the switch to chloramination has been
somewhat slower than expected. The 2004
AWWA secondary disinfection practices
survey found that 29 percent of community
water systems currently use chloramines
for secondary disinfection and that another
3 percent are converting to chloramine use
(Seidel et al. 2005).
Switching to chloramines is certainly
not easy and requires advance planning.
Utilities considering such a switch need
to consider issues ranging from public
perception to compatibility of chloramines
with the distribution system. Optimizing
Chloramine Treatment—Second Edition
(2004, order #90993), an update to an
earlier report, is a manual on the use of
chloramines and the role they play in water
quality improvements for drinking water
utilities. Using documented information
from 68 utilities that use chloramines, the
report identifies critical parameters for
controlling chloramination and spells
out a chloramination optimization strategy.
A Guide for the Implementation and Use
of Chloramines (2004, order #91018F)
summarizes the current state of knowledge
regarding chloramine use and synthesizes
the information into step-by-step procedures
for using chloramines in a water system.
Finally, Long-Term Effects of Disinfection
Changes on Water Quality (2007, order
#91169) documents the long-term effects of
disinfectant changes on distribution system
quality, including changes in microbial
quality, chemical quality, and aesthetic
quality. The report contains issue papers on
microbial quality, chemical quality (DBPs),
chemical quality (corrosion, metal release,
color, and particle characteristics), and
aesthetic quality impacts associated with
disinfectant changes.
Nitrification
Two-thirds of medium and large systems
in the United States that chloraminate
experience nitrification to some degree.
Nitrification can significantly diminish water
quality and can cause violations of coliform,
disinfectant residual, and nitrite limits, as
well as overall increased microbial growth in
the affected areas. Therefore, utilities using
chloramines are concerned about nitrification
events that occur when chloramines decay in
the distribution system.
When chloramines decompose, ammonia is
released and can be oxidized to nitrite. This
process, known as nitrification, is believed
to be facilitated by ammonia oxidizing
bacteria (AOB), which use the ammonia
as an energy source. These bacteria are
commonly found in drinking water systems,
and nitrification occurs when conditions
allow their numbers to rise. Although AOB
seem to be implicated in most nitrification
