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Water reclamation and nonpotable reuse is a practice that continues to spread throughout the U.S.
Nationally, the U.S. EPA estimates that an average of more than 1.7 billion gal of wastewater is reused per day. The states of Florida and California are leaders in reuse, with each state reusing an average of more than 500 mgd. Reuse in Texas and Arizona exceeds an average of 200 mgd, and states such as Nevada and Colorado are expanding reuse programs.
Recognizing the tremendous growth in reuse, in September 2004, the EPA released its updated Guidelines for Water Reuse. Originally published in 1992, the EPA’s objective for the document is to “summarize recommended water reuse guidelines for the benefit of water and wastewater utilities and regulatory agencies.”
Because the EPA views reuse as a local/regional issue, reuse regulation is highly decentralized, with individual states taking the lead. Guidelines serves as a tool for comparing the approaches of 34 states with reuse regulations in place.
Categories of reuse
There are a myriad of potential applications for reuse water. Ten categories of reuse applications are considered in Guidelines (see Table 1). On a volume basis, irrigation is by far the most common application of reuse water. As an example, more than 60% of all reuse water in Florida is used for irrigation (see Figure 1). Each reuse category has different regulations that are focused on matching the level of treatment to the intended use while providing sufficient protection of human health. Although a good deal of commonality exists between regulations for each category, details vary among states. In addition, not all categories are regulated by each state. For drinking water utilities, the reuse category of greatest interest is indirect potable reuse.
Regulation of indirect potable reuse
According to Guidelines, indirect potable reuse consists of “the use of reclaimed water to augment surface water sources that are used or will be used for public water supplies or to recharge groundwater used as a source of domestic water supply.” Guidelines avoids addressing the issue of planned versus unplanned indirect reuse. It does note, however, “Unplanned indirect potable water reuse is occurring in many river systems today.”
Nonetheless, the prime characteristics defining indirect potable reuse are that it consists of the “introduction of reclaimed water into the raw water supply for the purposes of increasing the total volume of water available for potable use” and its “proximity to subsequent withdrawal points.”
Clearly, much latitude is granted to the states in determining whether a reclaimed water project is indirect potable water reuse. As an example, Florida regulates reclaimed discharges to surface waters used as potable water sources that are less than 24 hours travel time upstream from the point of withdrawal for potable treatment as indirect potable reuse. Table 2, extracted from Guidelines, summarizes treatment and water quality requirements for several states that are pioneering indirect potable reuse.
Table 2 illustrates the variety of regulatory approaches being taken by the states. Even where specific regulations exist, indirect potable reuse is handled very much on a case-by-case basis. This indicates that regulatory agencies consider reuse highly site specific. Guidelines does make some general recommendations with respect to the minimum requirements any indirect reuse project must meet. These are summarized in Table 3.
The number of issues surrounding water reuse and indirect potable reuse addressed in Guidelines is far too many to capture in a single article. The interested reader can download a copy of the 2004 update of the Guidelines for Water Reuse from the U.S. EPA at www.epa.gov/ORD/NRMRL/pubs/ 625r04108/625r04108.htm.