Reuse of brine from desalination

Abstract

NoBriner (www.nobriner.org) aims to develop a technology to manage brine, a byproduct from the desalination process when producing safe drinking water from saline water sources. As a solution, a zero-liquid discharge desalination method, based on spray evaporation, is targeted - as a stand-alone solution, which can be combined with various desalination processes and heat sources. Furthermore, for application in rural areas with poor access to infrastructure, the technology is required to be low maintenance. Literature study was performed on characteristics of different desalination processes, with a focus on reference solutions for zero liquid discharge of brine as well as on system aspects in relation to the aimed NoBriner spray evaporation solution. Brine characteristics were determined experimentally (sample from Kenya) and by database screening. Investigations on sustainable implementation focused on social aspects and available infrastructure, dependent on the location. Furthermore, reference solutions for brine utilization were studied. The potential market was explored for brine as a multifunctional product. NoBriner worked on business development regarding the outlook of potential clients and projects. Zero-liquid discharge of brine was theoretically investigated by means of detailed models for droplet evaporation of pure water and brine. Literature findings were utilized to build and a standalone simulation program in Python. It was possible to verify the droplet evaporation model for pure water, which was utilized for experimental spray evaporation setup dimensioning. Thus, when brine is experimentally tested, the model can be updated in the future. To facilitate a future experimental validation of the zero-liquid discharge concept, DTU Byg planned an experimental spray evaporation setup. Components were selected and sized - at this stage the setup could be realized at DTU Byg after the necessary material (pipes, fittings, spraying equipment) is purchased. Furthermore, NoBriner and DTU Byg developed models for extended theoretical investigations: a) Solar electricity production assessment – a python tool was developed; The solar electricity assessment tool was verified with a public database. It can be utilized for holistic planning of stand alone solutions requiring electricity to power fans and pumps. b) system simulation utilizing solar thermal collectors – a TRNSYS spray evaporation model was developed. The TRNSYS model was successfully applied in a fist, simplified system scenario with a solar collector model and meteorological data from Nairobi, Kenya. Assumed parameters (performance of spray evaporation unit in dependency of ambient conditions) must be experimentally verified, then the model could be applied to design a spray evaporation system. Based on calculations results of the simplified system scenario, a stand-alone solution for zero liquid discharge is difficult to realise - experimental work is crucial to clarify applicability. All project results are documented in this report. Collected literature, developed simulation models and calculation sheets were made available to NoBiner for further development of brine management solutions.