Design of end-of-pipe zero liquid discharge systems under variable operating parameters

Abstract Zero-liquid discharge systems have proven to be quite effective as a long-term brine management strategy. The availability of powerful modelling and optimization tools for the design of cost-effective zero-liquid discharge systems is vital, so as to ensure that only the best -performing systems are designed, constructed and operated. To date, the design of zero liquid discharge systems has been modelled in terms of flow rate only, without accounting for the effect of other parameters such as the feed salinity, temperature and pressure. The focus of this work is to integrate additional operating parameters (mainly temperature, salinity and electricity pricing), into a modified optimization model and to determine, more accurately, the best zero liquid discharge system configuration based on specific brine feed characteristics. The proposed model has been implemented using a case study and sensitivity analysis is performed to determine the most optimal structure under different inlet conditions. The results indicate that the optimal configuration is highly sensitive to brine temperature, and salinity. Moreover, this work also demonstrates how non-brine related conditions, such as electricity pricing, affects the design of such systems. When compared to Mansour et al. (2018), the capital costs were comparable, however, the operating costs of ZLD systems have been captured more effectively after introducing additional model parameters.