3. Decrease NOM/DOC precursors.
Both hydrophobic and hydrophilic
NOM fractions should be removed,
but preference should be given to
4. Decrease Cl2/N ratio.
5. Decrease chloramine residuals. The
amount of DXAA reduction was limited;
thus, this method should be used as a
Advanced Water Treatment of Estuarine
Water Supplies experimented with
combining disinfectants and treatment
scenarios to minimize DBP formation. For
the water tested, the following combination
of disinfection yielded the lowest THM and
1. Pre-oxidation with chlorine dioxide.
2. Intermediate oxidation with ozone.
3. Post-filter disinfection with UV.
4. Final disinfection with chloramines
without a contact period between
addition of free chlorine and ammonia.
Selection and Implementation
Numerous drinking water utilities have
modified their treatment practices to
comply with DBP regulations. Some of
the experiences were documented in
two reports: Case Studies of Modified
Disinfection Practices for Trihalomethane
Control (1990, order #90574/project #201)
and Case Studies of Modified Treatment
Practices for Disinfection By-Product
Control. Details of each case study can be
found in these reports. The main issues that
influenced a utility’s decision on selecting
and implementing a treatment practice
modification were regulatory compliance,
utility business, and customer acceptance.
The latter report recommended that for
selection of a DBP control technology, a
utility should consider compliance with
not only the DBPR but also other water
quality objectives such as the Enhanced
Surface Water Treatment Rule, the Total
Coliform Rule, and the Lead and Copper
Rule. Alternatively, better optimization of
existing treatment processes might be a
After selecting a technology, the utility
should follow the steps below for successful
• The information used in the decision-
making process would need to be
summarized and presented to the utility’s
governing body and consumers.
• To persuade the governing body, the
utility would need to make a series of
presentations to provide background
information and the underlying logic for
implementing the selected technology.
• The utility would need a public
information program to ensure consumer
• After approval of treatment modification,
the utility’s operating staff would need
• The utility would need an implementation
plan developed and supported by a
• The utility would need a contingency
plan to address how to handle expected
and unexpected problems during
• There might need to be shifts in the
overall operational strategy or operating
paradigms to make the modifications
• If implementation problems or tradeoffs
arose, the utility would need to resolve
some of them immediately, whereas the
others might need a period of adjustment.
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