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2.8 CHAPTER TWO
It is apparent that the EPA is now employing treatment technology and other mitigating
measures in addition to maximum contaminant levels (MCLs) for several of these new
rules.
Maximum contaminant level goals (MCLGs) have been established for some time for
most of, if not all, the proposed new standards. In moving toward establishment means
that the federal USEPA believes that the technology is available for treatment at a rea-
sonable cost to the consumer.
The trends in new contaminant additions to the rules, tightening of existing stan-
dards, and expansion of regulatory application should continue as new health issue and
treatment research indicates the need and potential resolutions. To make the problem
of producing acceptable quality water even more complicated, the treatment plant de-
signer now also has to contend with the possibility of unusual biological and toxic con-
taminants introduced into the water supply by terrorist activity. It is apparent that treat-
ment facilities now must not only accommodate changes in regulatory requirements, but
also continue to handle changes in influent raw water quality. As the rules become more
stringent, it will become more difficult to handle rapid changes in quality due to nat-
ural causes such as intense rainfall and runoff. It will be even more difficult to handle
"introduced" contaminants because of the unknown factor. Once it is introduced and
contaminants are discovered, temporary shutdown of treatment facilities may be nec-
essary. The tightening rules and the potential for unexpected contamination make wa-
ter quality monitoring facilities even more essential features of water treatment plan-
ning design and operation.
It is emphasized that the primary purpose of this brief discussion of the new proposed
rules is to illustrate the challenge presented to the design engineer in defining treatment
goals. The established and proposed water quality rules and standards shown in the tables
should serve only as a guide to the water treatment planner or designer. It is also essen-
tial that the details of water quality requirements be obtained from the appropriate state,
provincial, or other agency.

Regulatory Trends~Treatment Obsolescence

In general terms, the goal of the SDWA is to produce the most contaminant-free drink-
ing water that technology permits, limited only by the magnitude of treatment costs. As
technology has improved, particular MCLs have become more stringent. Since 1970, for
instance, turbidity limits have been reduced from 5.0 to 1.0 to 0.5 ntu and, under the In-
terim Enhanced Surface Water Treatment Rule, to 0.3 ntu. Some states may require even
lower limits. The first-stage TTHM (total trihalomethane) and HAA5 (five haloacetile
acids) limits recently became effective for average distribution system conditions. In the
near future these limits will be required for worst-case locations in the distribution sys-
tem. New regulatory requirements are continuously being added to the rules such as the
reduction of organic content in treatment and the reduction of arsenic content.
As the regulatory requirements become more stringent, currently accepted treatment
processes can and will become obsolete. If, for instance, turbidity levels in surface water
treatment are reduced to 0.20 ntu, there are several types of filtration that may not be ad-
equate operating in currently acceptable design modes. Such facilities may have to be re-
placed or, modified in operation, or supplementary filtration may have to be added. Some
current filtration processes do not reduce organic content at all or reduce organics to a
limited extent. These also may have to be replaced, modified, or supplemented in treat-
ment. Potential treatment obsolescence must be recognized in treatment selection to avoid
costly future changes.