Civil Engineering Reference
In-Depth Information
CHAPTER 3
Organic Compounds in Drinking Water
INTRODUCTION
It is estimated that over 5,000 new organic compounds are brought to market each
year. The vast majority of these represent no health threat, nor do they threaten con-
tamination of the nation's water supplies. Nonetheless, this constant new production
of compounds, coupled with an ever-improving analytical capability, means that the
detection of heretofore unreported organic compounds in both ground and surface
waters is a growth industry. It is essential that water industry professionals understand
the nature and source of the organics threat, and the growing body of drinking water
regulations governing these compounds. It is impossible for a single chapter, or even
a single topic, to adequately cover this topic. This chapter will focus on the currently
regulated volatile and synthetic organic compounds, natural organic matter that serves
as the precursor for DBPs, and the most important emerging organic chemical threat
of the past decade, MTBE.
ORGANICS MONITORING
There are currently over 150 drinking water chemical contaminants that have been
either proposed listed or finalized for regulation. Of this number, over 100 are organic
compounds. Regulated contaminants have risen substantially over the past two decades
and will continue to rise into the foreseeable future. Which utilities monitor for which
organic compounds (or group of compounds) and with what frequency is usually de-
termined based on the size of the utility, the nature of the water source, and the history
of contamination. Because of the substantial expense of monitoring and the serious
consequences of violating an MCL, proper collection techniques, chain of custody,
and analysis is crucial. Table 3-1 presents the sampling methods and criteria for dif-
ferent classes of organic compounds.
VOLATILE ORGANIC COMPOUNDS
Volatile organic compounds (VOCs) are so called because of their distinctive common
property, which is high volatility relative to most other organic substances. A practical
definition of a VOC is an organic compound having a Henry's constant (see Chapter
9, ''Aeration'') greater than 10. Table 3-2 lists the 16 VOCs of greatest concern in
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