Numerical and experimental investigation of a DC-powered RO system for Sri-Lankan villages. (January 2022) - Li, Qiyuan
Abstract: High operation and maintenance costs, and 'last-mile' issues for populations not connected to municipal water infrastructure, have limited the utility of centralized reverse osmosis (RO) systems to alleviate water availability issues for rural communities. To address these challenges, a decentralized RO module which employs tubular RO membranes was designed and investigated. The system represents an appropriate technology because it requires minimal pretreatment and it fits in self-contained, low-profile suitcase. This compact desgin also incorporated innovative 3D printed static mixers to minimize salt concentration polarization and to improve performance. Since grid electricity may also be discontinuous in the target use cases, the system was tested with two direct current (DC) power solutions: a photovoltaics-battery configuration and an alternator-battery. The final prototype weighs less than 15 kg and was found to have a production capacity of ∼8 L/h, consuming ∼100 W of pumping power. Experiments of the prototype module revealed a 96% rejection rate of salt from a 1000–2000 ppm synthetic groundwater solution and a >99% rejection coefficient for bovine serum albumin protein and humic acid. From these performance metrics, it was estimated that 36 sets of this decentralized system (with a total CapEx of US$23, 400) could provide drinking water for ∼600 rural households at a unit cost of water of 1 LKR/L (0.005 USD/L) in Sri Lanka. Overall, this study demonstrates how computational modeling and 3D printing can be leveraged to develop a compact and cost-effective decentralized RO package that could be rapidly deployed to water-stressed rural areas and in disaster relief applications. Graphical abstract: Image 1 Highlights: A plug-and-play, compact DC driven mobile RO desalination system was developed. Both alternator-battery and solar PV- battery power solutions were designed and tested. The system is less than 15 kg and can produce 8 L/h of water with 100 W of power. Rejection of 96% for salt and >99% for both protein and humic acid was observed. The levelized cost of water of water was found to be < 0.005 USD/L.