Singe use and disposal of water may be unsustainable, and direct potable reuse offers unified treatment and distribution and indefinite cycles of reuse. However, most current implementations recycle only ~20%, and pass concentrated contaminants for disposal. In contrast, advanced oxidation-based net-zero water (NZW) systems eliminate water importation and exportation. Systems comprising biological treatment, aerated aluminum electrocoagulation, vacuum ultrafiltration, and advanced oxidation have produced 85% of indoor potable water, made-up with 15% rainwater, and 15% potable water for outdoor use. The systems met all microbial and chemical drinking water standards, greatly exceeded microbial inactivation guidelines, and mineralized chemical oxygen demand (COD), hormones, personal care products, and pharmaceuticals to below detection. Further, non-biological, UV-ozone treatment allowed 85% shower and wash water reuse, e.g. for portable deployments at remote Ebola and other health care units. The second-order rate constant for OH* oxidation of secondary effluent organics was estimated at 1.24 x 107 M-1 s-1, and of micro-filtered greywater organics at 2.19 x 107 x 107 M-1s-1. The electric energy demand was estimated at 1.73 – 2.49, 7.0, and 5.10 kWh/m3-order COD removal, for the peroxone, UV-hydrogen peroxide, and UV-ozone systems, respectively. Kinetic modeling predicted UV-ozone mineralization, considering competing OH* formation pathways. Beyond providing 100% water reuse and emerging organics mineralization, the system is equivalent in cost to conventional technology, and economical at scales down to 100 homes per plant. Importantly, a 1 MGD NZW system may save more energy than is consumed in water and wastewater treatment and conveyance combined. That is, thermal energy imparted by domestic and commercial water heaters, representing ~4% of US primary energy demand, is retained in the water, which returns to use warm and needing little re-heating. In fact, a sub-arctic system may save four times the energy needed for treatment and conveyance, addressing needs for above-grade and freeze-protected piping. Moreover, the system is locatable anywhere, needing no water source or wastewater disposal. Hence, they can be co-located to pass treated water through electric power plants, for delivery of previously waste thermal energy representing ~24% of US primary energy to homes via the water distribution network. Monitored regulatory demonstration is recommended.

Advanced oxidation-based net-zero water technology: Opportunities for percent-level national energy demand reductions

256th National Meeting (2018)

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