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ments. This report provides guidelines and suggestions regarding how such evaluations should be carried out. Thorough evaluation of the risks of a proposed potable reuse project, in addition to full consideration of other options for potable water supply augmentation, is essential for a sound decision about whether the project is viable.
Chemical Contaminants in Reuse Systems
Municipal wastewater contains chemical contaminants of three sorts: (1) inorganic chemicals and natural organic matter that are naturally present in the potable water supply; (2) chemicals created by industrial, commercial, and other human activities in the wastewater service area; and (3) chemicals that are added or generated during water and wastewater treatment and distribution processes. Any project designed to reclaim and reuse such water to augment drinking supplies must adequately account for all three categories of contaminants.
The organic chemicals in a wastewater present one of the most difficult challenges a public health engineer or scientist faces in considering potable reuse. The challenge arises from the large number of compounds that may be present, the inability to analyze for all of them, and the lack of toxicity information for many of the compounds. Efforts to account for the total mass of organic carbon in water are further frustrated by the fact that the bulk of this material is aquatic humus, which varies slightly in structure and composition from one molecule to the next and cannot be identified like conventional organic compounds. These challenges are not unique to potable reuse systems. In fact, the most protected water supplies are those for which the smallest fraction of the organic material can be identified. For potable reuse systems, however, anthropogenic organic compounds pose the greatest concern and should be the major focus of monitoring and control efforts.
The following recommendations suggest several important guidelines to account for chemical contaminants of potential concern in potable reuse systems:
The research community should study in more detail the organic chemical composition of wastewater and how it is affected by treatment, dilution, soil interaction, and injection into aquifers. The composition of wastewater and the fate of the organic compounds it contains need to be better understood to increase the certainty that health risks of reclaimed water have been adequately controlled through treatment and storage in the environment.
Proposed potable reuse projects should include documentation of all major chemical inputs from household, industrial, and agricul-