Mehul Patel, P.E, Executive Director of Operations and the Groundwater Replenishment System, The Orange County Water District
The potable water reuse industry in America had its birth not long ago in Southern California out of need for a new source of water. Indirect potable reuse, blending advanced purified wastewater in a groundwater basin, reservoir or other natural water source before it is pumped and sent to homes, was used in Los Angeles County’s Montebello Forebay project starting back in 1962 and in Orange County’s Water Factory 21 in 1976. Soon thereafter, in 1978, it was used in Fairfax County by Virginia’s Upper Occoquan Service Authority.
Today, there are 20 potable reuse facilities in seven states within the United States and that number is growing.
The biggest challenge to the industry is the lack of federal regulation—a comprehensive set of standards and requirements for reuse projects. We are on the “Wild West” segment of water reuse’s historical timeline. Those water reuse agencies that are moving forward utilize state laws and requirements, which required working closely with state agencies that set drinking water standards, ahead of the federal government. This difficult and time-consuming law-making process doesn’t help to incentivize projects in other states where no state regulations exist for potable reuse.
"Add nationwide standards and we will have the perfect solution to encourage widespread water reuse that could enable a direct flow to homes of an even better product for less money to the consumer"
Additional challenges include the intense use of energy to provide quality water. That energy component has yet to be optimized and needs a greater value on return. The revolution that made water reuse possible for the masses was reverse osmosis. We have seen a great leap of improvement in membranes since their use in 1976. It originally took 600 psi to filter and now it takes 150 psi, and we make more water. After more than 30 years, the membrane material is virtually the same and it’s still expensive. We see promise in new materials from the aerospace industry that are now in the experimental stage, but they, too, have some limitations and the cost is exorbitant. There is a trend away from membranes and towards granular activated carbon with oxidation, which combines an oxidant and energy together instead of a membrane. This lowers the high energy requirement of reverse osmosis while also eliminating a continuous reject waste stream.
Finally, technology that allows real time, online pathogen detection needs to be created. Those in the industry currently take samples of the purified water, send it to a laboratory and receive the results back within 24 hours. We use a surrogate approach and relate the results to contaminants that shouldn’t get through to those that do. Environmental buffers ensure that any remaining contaminants are naturally filtered and mixed with billions of gallons of water that dilute them further. There is a welcome time factor, usually 6 months before pumping, to address any concerns should they arise.
Water reuse in this country is evolving towards direct potable reuse (DPR). California is on target to provide DPR guidelines by 2023. For DPR to happen, regulators want real time testing data to avoid acute health risks. As these new technologies are brought to market to address water quality, the Water Research Foundation and organizations that have applied research programs will ensure with more certainty the safety of the product water. Technological advancements in energy and treatment costs should lower the price of the purification process. Add nationwide standards and we will have the perfect solution to encourage widespread water reuse that could enable a direct flow to homes of an even better product for less money to the consumer.