supplies in the 1960s and 1970s. Fortunately, the disinfection workhorses
of chlorine and chloramines were able to control both classes
of microbial contaminants. In the 1980s, several highly publicized
outbreaks of giardiasis made control of the responsible pathogen a
priority. Chlorination was ramped up, and ozone was installed on
many water supplies as an additional barrier. The outbreak of cryptosporidiosis
in Milwaukee in April of 1993 created a new challenge
that was met with improved filtration efficiencies and the implementation
of UV disinfection.
Figure 2 shows how the Los Angeles Department of Water and
Power answered the challenge of the need for more barriers against
pathogens. Its ozone/direct filtration plant was built in 1986 to control
turbidity. The recent addition of UV disinfection along with chloramines
in the distribution system will put LADWP in the forefront of
regulatory compliance. The need for the UV system on the effluent of
the uncovered Los Angeles Reservoir is identified in Table C.
In 1974 the weakest links in many water systems were uncovered
finished water reservoirs where treated water was contaminated with
bird wastes, bacterial regrowth, algae growth, airborne dust deposition
and deliberate disposal of wastes into the reservoirs. Table C shows only
a few examples of the progress in covering reservoirs or treating the
effluent from uncovered reservoirs to comply with regulatory requirements
that emanated directly from the SDWA. Portland, OR has resisted
covering or treating the effluent from its uncovered reservoirs, even
16 SOURCE summer 2014
in the face of contamination by dog feces, bird droppings and the death
of a person infected with Hepatitis A. However, under the Long Term
2 Enhanced Surface Water Treatment Rule, it appears the utility will
be brought into compliance by 2020 and water quality for customers
downstream of these contamination points will be improved.
Under the first trihalomethane regulation, and with the enhanced
requirements of the Stage 1 and 2 Disinfectant/Disinfection Byproducts
regulations, there have been dramatic reductions in the exposure
of tap water consumers to disinfection byproducts. While we don’t
have DBP occurrence data that shows the most recent improvements,
one study published in 2002 showed significant reductions in trihalomethanes
(THMs) quantified in the NORS study (1974) compared to
the results of the Information Collection Rule (ICR) (1997 and 1998).
The dramatic reduction in the 90th percentile concentrations (P90) of
trihalomethanes demonstrates that DBP regulations under the SDWA
have been particularly effective in reducing high concentrations of
THMs in the nation’s distribution systems (Figure 3).
It is well known that progress in regulatory compliance and installation
of improvements to small water systems has lagged behind
the large systems, often because of limited capital and limited access
to expertise. However, a project undertaken as a UCLA senior class
project demonstrates how much progress has been made. As a student
supported charity, a summer camp serving inner city children
is now having its water system improved using the expertise of professors
and students. In 1974, there was no treatment of the surface
water that was taken from the nearby creek and served to the campers.
Today, this transient, non-community water system serving about
250 campers at a time has bag filters and a chlorination system. The
camp has to comply with CT and turbidity requirements, and monthly
bacteriological samples ensure that contamination is not taking place.
This is what I call improvement in public health protection.
Where to From Here?
Currently, USEPA, water utilities and the entire water community
invest large amounts of time and money evaluating contaminants
to be regulated. The fourth cycle of the Contaminant Candidate List/
Table C. Progress Covering Finished Water Reservoir
Figure 3. Progress Made in Reduction of Trihalomethane Exposure (P90 denotes the
concentration of THMs for which 90 percent of water utilities surveyed were lower)
Figure 2. UV Installations at the Los Angeles Aqueduct Filtration Plant (Source:
Los Angeles Department of Water and Power)