What types of treatment are considered to affect the measurement of the unregulated contaminants?
Finished drinking water is the focus of unregulated contaminant monitoring, because the UCMR is designed to assess both contaminant occurrence and human exposure. When unregulated contaminant monitoring is performed at source water locations and the results are negative, it is reasonable to assume that water treatment will not introduce any of these unregulated contaminants. However, some of these contaminants may be affected by treatment and the only way to evaluate exposure is to monitor the finished water. For unregulated contaminant monitoring, EPA considers water treatment to include any physical or chemical process which improves the suitability of the water for consumption and/or alters the composition of the source water. These processes include, but are not limited to, processes such as filtration, aeration, coagulation, sedimentation, softening, oxidation, and disinfection. For blended water, if processes are applied to the blend prior to the first customer, unregulated conta
