Resource recovery by freezing: A thermodynamic comparison between a reverse osmosis brine, seawater and stored urine

Eutectic freeze crystallization (EFC) can be used to recover several resources from wastewater streams by operating at sub-zero temperatures where both ice and salts form. The type of salt, the amount formed and the salt purity at these conditions will determine the potential profit for a specific wastewater composition. While thermodynamic modelling has been shown to accurately predict the type of salt and yield of this salt, it has not been used to predict the potential financial benefits of a wastewater when operating under EFC conditions. In this paper, a generic equation and procedure is developed to estimate the potential financial benefits for three different types of "waste" waters: an RO brine, sea water and stored urine. This methodology is aimed at equipping engineers with a valuable tool to be used as a means of determining the preliminary feasibility of an EFC process without having to run sophisticated and time-consuming experiments. If shown to be profitable, a more detailed kinetic study can be conducted to facilitate the detailed technical design and a cost benefit analysis of utilising an EFC process for a specific type of wastewater can be perfomed.