Drought Supplies: Making Direct Potable Reuse More Palatable
Recent severe droughts across the U.S. have highlighted the need for new water supplies or at least different management strategies. One source that often comes up in this conversation is direct potable reuse (DPR). The water has already been developed, often at great cost and is readily available in the utility’s system. And once treated, it becomes “new water.”
However, high capital and operations and maintenance costs, public perception issues and the potential for increased health risks have relegated DPR to the supply option of last resort. This status was exemplified by emergency implementation of DPR projects such as those in Big Spring, Texas (2013) and Wichita Falls, Texas (2014). But expedited implementation of DPR projects only increases the cost and heightens customer anxiety. And when it finally does start raining, it is tempting for utility managers to mothball these high cost plants, allowing DPR to quickly fade from the public consciousness.
What if we could lower the cost of DPR by having a secure place to bank a drought supply? This would allow a much smaller plant, operating continuously, to deliver the required peak capacity during drought. Continuous operation also would elevate operator competency and increases opportunity for public education and outreach. For many utilities, this secure place is literally under their feet.
Most municipalities historically relied on groundwater for public supply before demand growth outstripped the aquifer carrying capacity. With the demonstrated ability to store large volumes of drinking water for extended periods, aquifer storage and recover (ASR) can be used to bank DPR supplies. This storage also has the added benefit of providing a buffer between the treatment plant and the tap, allowing time for more comprehensive monitoring of product quality and further conditioning the water as it moves in and out of the aquifer. Coupling DPR and ASR could just be the thing to make DPR more palatable for water supply purveyors worried about meeting needs during the next drought.