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%.

Decentralized water treatment consists of a variety of water treatment techniques for dwellings, industrial facilities, homes, and businesses independent of the power grid. According to the United States Geological Survey, brackish groundwater is abundant in the southwestern states including California; hence it can potentially be considered a new source for California’s water portfolio. Most of membrane-based desalination technologies (e.g. reverse osmosis) have high energy demand and cost. Using renewable energy (mostly solar photovoltaics) in concert with membrane-based water desalination can be utilized to develop decentralized and off-grid brackish water desalination systems especially for remote and rural regions. In this paper, the results of a case study on decentralized off-grid brackish water system have been presented and discussed. The system utilizes a high pressure pump that can provide a feed flow rate of 2.2 gpm of at 140 psi. The system is run by solar photovoltaic panels through a battery bank. The results of the study show that the system is capable of treating brackish water at a salt rejection rate of more than 97.5% and a recovery rate up to 80%.

Decentralized Renewable Off-grid Wastewater Treatment, DANIEL ANDRADE, KYLE MILLER, MOHAMMAD MASOUD MODABERNIA, THUAN JOHN NGUYEN, JUSTINE NGUYEN, and REZA BAGHAEI-LAKEH* (Mechanical Engineering Department, Calif. State Polytechnic Univ. at Pomona, Pomona, CA, 91768, rblakeh@cpp.edu) The concerns of water availability has risen due to the stress from high water consumption and the effects of climate change. In the past, California has experienced extreme drought conditions where a series of executive orders have been issued to address concerns and conserve water. Even after the expiration of the exceptional drought condition, more than 10 million people still live in drought condition in California. In this presentation, a case study of a decentralized graywater treatment for non-potable use will be discussed. DROWT (Decentralized Renewable Off-grid Water Treatment) project is an innovative water recycling system which is expected to have a tremendous role in reclaiming a major proportion of water for non-potable purposes without having any carbon footprint. The research team at Cal Poly Pomona, with the support of Metropolitan Water District of Southern California, are developing an off-grid solar-powered greywater treatment system for single households and remote locations. The system consists of three stages of treatment, including a microfiltration, solardriven reverse osmosis, and an ultraviolet disinfection unit. These treatments will remove particles of dirt and food, traces of organic chemicals and inorganic chemicals, etc. All electrical components of the system will be powered by the photovoltaic panels to make the system completely grid-independent. To further improve the power efficiency, the energy recovery device is also added to reduce the energy consumption of the system. The product of this project will be capable of reclaiming 90 gallons of water per day while recovering 63% of residential greywater. In this presentation the preliminary design of the system will be discussed and the energy consumption of the system will be compared with similar studies.