Design and Testing of a Solar-Driven Wastewater Treatment Unit for Off-Grid Applications

Abstract

The decline of surface water sources along with periodic droughts has introduced new challenges for the state of California. In order to keep up with the increasing demand for water, the state is heavily relying on imported water from the north to Southern California as well as importing water from the Colorado River. The imported water has a large carbon footprint due to using grid power for water transport. Water reuse (reclaimed) is considered as one of the solutions to reduce the dependency of state on imported water. The research team at Cal Poly Pomona, is developing an off-grid solar-powered greywater treatment system for non-potable use in single households. Greywater is the drained water from bathroom sinks, showers, tubs, and washing machines; not including wastewater from toilets or kitchen sinks. Treating greywater on-site can provide significant water savings, and can reduce the carbon footprint of desalination using solar panels. The developed system is comprised of a three-stage treatment train: micro-filtration, solar-driven reverse osmosis, and ultraviolet disinfection. The end product of the project is capable of reclaiming 90–100 gallons of water per day which is about 60% of residential greywater waste. The system removes large suspended particles (particles of dirt, food, etc.) as well as organic and inorganic dissolved contaminants. It is demonstrated that the system can provide a permeate quality that agrees with recommended guidelines for reclaimed water. The system has a recovery rate of up to 62%.