The following conclusions and recommendations emerged from the committee's deliberations:

ARTIFICIAL RECHARGE: A VIABLE OPTION

Artificial recharge of ground water using source waters of impaired quality can be a viable way to augment regional water supplies—primarily for nonpotable purposes but for potable purposes under appropriate conditions—and at the same time provides an avenue for wastewater management.

Artificial recharge with waters of impaired quality has been practiced successfully in various pans of the United States and elsewhere for many years. Source water options include treated municipal wastewater, stormwater runoff, and irrigation return flow. Treated municipal wastewater and stormwater runoff are the two most commonly used sources; experience with the intentional use of irrigation return flow is scarce and not well documented. Recharge can be accomplished either through surface infiltration methods or through injection directly into the aquifer by wells. Hydrogeologic conditions, land availability, and the purpose of the recharge dictate the method of recharge, which in turn dictates the required pre-recharge treatment of the source water. Surface infiltration methods are used far more frequently than wells because of economic and operational considerations. However, wen recharge is increasing because suitable sites for surface infiltration are not always available.

Ground water recovered from aquifers recharged with waters of impaired quality has been used for various purposes, ranging from landscape irrigation to potable supply. The desirability of using such waters for various purposes depends on the quality, availability, and cost of alternative sources of supply and varies considerably by site and source. One advantage of nonpotable reuse is that it releases other, higher quality sources for potable use.

A fundamental conclusion of this report is that impaired quality waters used to recharge ground water aquifers must receive a sufficiently high degree of pretreatment (prior to recharge) to minimize the extent of any degradation of ground water quality, as well as to minimize the need for any extensive post-treatment at the point of recovery. With surface infiltration systems, considerable quality improvements can be obtained as the water flows through the unsaturated zone to the aquifer, this soil-aquifer treatment (SAT) reduces pretreatment requirements.

Although some impacts of artificial recharge of ground water with source waters of impaired quality are not understood with complete certainty, experience with recharge projects has failed to show (within the limitations of toxicological testing) that water recovered from the aquifer poses greater health risks than currently acceptable potable water supplies. The state of our knowledge



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