Powering Desalination through Solar Energy

Abstract: The purpose of this research project was to identify the discharge information that permitting agencies need and the decision-making process they go through to permit discharge methods in order to help desalination project proponents focus and expedite their permitting efforts. The project documented seawater reverse osmosis (SWRO) discharge regulatory issues and provided a critical overview of facility discharge-related information required for permitting desalination projects in the United States and selected countries with advanced environmental regulations and experience in implementing seawater desalination projects. Information was gathered from the three key U.S. states (California, Florida, Texas) where interest in SWRO desalination has been highest. Due to the more extensive international experience with SWRO desalination, information was also obtained from the countries of Australia, Israel, and Spain – all countries of significant recent large-scale SWRO desalination projects. Case studies of 11 SWRO plants and analysis of regulatory systems and permitting processes supported detailed definition of the decision-making process to set discharge permit limits, as well as defining environmental and other regulatory issues associated with concentrate regulation.

Abstract: Substantial parts of the U.S., particularly drier landlocked regions, are facing acute water shortages and water quality issues that decrease agricultural productivity. Reduced crop yields cause billions of dollars in losses annually, affecting the livelihoods of thousands. A combination of population growth, inefficient agricultural practices, and resource demanding consumption trends is only expected to increase pressure on our water supplies. This research proposal seeks to address water and food security issues by cost-effectively and energy-efficiently enhancing water quality and water supply in greenhouses; a $22.93 billion dollar industry in 2017 that is rapidly growing at an annual rate of 8.92%. Greenhouses widely practice desalination of salty irrigation water to improve their operations. However, currently used desalination methods do not tailor greenhouse waters based on crop requirements. This work investigates a fully integrated desalination solution that treats and tailors brackish source waters ingreenhouses to save fertilizer and water. Specifically, this project experimentally studies multi-ion transport in and assesses the economic viable of monovalent selective electrodialysis (MSED). MSED allows for the selective removal of monovalent ions damaging to crops and the retention of divalent ions beneficial for crops, unlike the widely used reverse osmosis (RO), which removes all ions from greenhouse source water. First, we evaluate the techno-economic feasibility of MSED compared to other brackish desalination technologies for agricultural applications, based on primary market research we conduct with over 70 greenhouses. These include conventional technologies, such as reverse osmosis (RO) and electrodialysis (ED), and advanced technologies, such as closed circuit reverse osmosis (CCRO). The analysis determines the levelized costs of water, the capital costs and energy requirements of these technologies, and how these vary with feed salinity, system capacity and recovery ratio. Then, we build a bench-scale setup to experientially characterize MSED membrane properties, including monovalent selectivity, ion transport, limiting current and resistance, for multiple brackish feedwaters and for two sets of MSED membranes: the widely used Neosepta ACS/CMS membranes and the new Fujifilm Type 16 membranes. Both MSED membranes show notable monovalent selectivity for all tested compositions, reflecting the potential of the technology for selective desalination in greenhouses. The measurements are compared to a model for MSED in multi-ion solutions. The model predicts multi-ion transport for the Neosepta and Fujifilm MSED systems within 6% and 8%, respectively.  

Abstract: This study proposes a simple design method of the Reverse osmosis (RO) system in RO brackish water desalination plants. This method is based on the application of maximum available recovery without scaling of any of the compounds present in the water as silica, calcium carbonate, calcium sulfate, barium sulfate, strontium sulfate, and calcium fluoride, and membrane manufacturer design guidelines, and the plant production. Although the method was originally conceived for application to subterranean brackish waters in the Canary Islands, Spain (principally Gran Canaria, Fuerteventura and Tenerife), it can be extrapolated to other types of region and water treatable with RO systems. The required input data are the chemical composition of the feed water, pH, temperature, silt density index membrane manufacturer design guidelines, and the plant production. The programmed method then determines the design of the RO system. The method whose procedure is described graphically and analytically can be used as an aid in design optimization of RO brackish water desalination plants with acid-free pretreatment processes and only the use of scale inhibitor using spiral wound membranes. Practical applications are presented. The final results for different types of feed water and capacities are showed.