Flint NBC News Interview - Flint TTHMs
Attached is a summary of the interview | had with Flint NBC 25 News late
yesterday.....sorry this summary is late as | am receiving incoming calls from Flint
residents...
Michael Prysby, P.E.
District Engineer
Office of Drinking Water and Municipal Assistance
517 290-8817
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Flint NBC 25 News Interview
Flint TTHMs
January 5, 2015
Walter-Smith Randolth, reporter, from Flint NBC 25 News conducted a
telephone interview with me for broadcast on Flint local television
concerning the TTHM violation in Flint’s drinking water. I led the
interview and provided Mr. Randolth an opportunity for follow-up
questions. Below is a summary of topics that were presented.
TTHM violation — What does this mean for Flint residents? The
TTHM violation notice to residents is not an immediate public health
emergency since the health-effects posted in the notice require long-
term exposure to TTHMs (over a significant portion of an individual’s
lifespan). TTHMs commonly occur in public water systems that
disinfect with chorine due to the reaction between chlorine and
naturally occurring organic compounds (total organic carbon) in the
source water. Surface water sources, including the Flint River
watershed, typically have higher levels of naturally occurring organic
compounds.
What is the DEQ’s Role? The DEQ is working in collaboration with
the city to ensure long-term public health protection and to keep the
public informed. We are working with the city to help identify
improvements in treatment and operation of the distribution system to
reduce the levels of TTHMs. We are assisting the city with public notice
requirements (when to post/contents). With our assistance, the city has
proceeded with an operational evaluation of the water system ahead of
state and federal requirements.
DEQ’s perspective of the situation: _ The Flint River source is more
difficult to treat since it requires more disinfection to maintain
bacteriological intergrity. Increased disinfection; however, when
combined with higher levels of naturally occurring organics results in
elevated levels of TTHMs that form over time out in the distribution
system. The TTHM concentrations that developed in the system were
more than anticipated due to several reasons:
1. Flint did not immediately change their mode of distribution
system operation after switching sources to account for higher
TTHM formation potential of treated water from Flint’s WTP.
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T explained that TTHMs require time to form and are not fully
developed in the treated water that enters the distribution system from
the WTP. Water from Detroit; however, is several days old when it
reaches Flint; thus the majority of the TTHMs are developed. TTHMs
were also lower given the source water (Lake Huron). Flint’s
historically operated the distribution system in a manner that created
conditions favorable for stagnation. This methodology of operation was
not changed (initially) when switching to the Flint River; thus, this
condition was one of several factors contributing to higher levels of
TTHMs. Other factors included; higher TTHM formation potential in
the Flint River (already explained above) and higher chlorine
application rates at treatment plant to maintain bacteriological
integrity.
I further explained that TTHM levels in the most recent quarter have
dropped for two main reasons:
1. Action taken by the city including; improving dist. system
operation to reduce stagnation, treatment changes (complete
softening), reduced chorination, system flushing, valving
improvements
2. Seasonal fluctuation of organic compounds in the Flint River.
Less organic loading in the winter months.
END of MY DISCUSSION
Mr. Smith-Randolf asked for my comment to the following
this problem is occurring in Flint? Is there
a problem with the water system? This was not an issue when Flint was
on Detroit water.
I responded by summarizing some of the key points discussed above
including:
Dist system operation (storage facilities and valving)
TTHM formation potential in Flint River vs. Detroit and age of
incoming water
e High chlorine dosages to maintain bacteriological integrity
e Treatment practices at WTP (partial by-pass of softening)
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