A pretreatment process for brackish water and brine desalination -

Abstract

In response to the increasing demand for fresh water worldwide, water reuse and desalination have been successfully employed as alternative methods of freshwater supply over the last few decades (Elimelech and Phillip, 2011). Specifically, reverse osmosis (RO) has gained significant appeal as one of the major processes for desalination, representing up to 80percent of the total number of installed desalination plants globally (Greenlee et al., 2009; Valavala et al., 2011). Due to technological enhancements and reduction in cost requirements, RO is viewed as an energy-efficient process, especially for the desalination of brackish water (Lauer, 2006; Elimelech and Phillip, 2011). Nonetheless, the RO process has several limitations, the most hindering of which is membrane fouling due to particulate and colloidal matter, inorganic compounds, organic substances, and biological growth (Prihasto et al., 2009; Valavala et al., 2011). Not only does membrane fouling reduce the efficiency and lifetime of the RO membrane, but it also incurs additional costs to operate the system due to increased energy demand and frequent cleaning (Bodzek et al., 2011; Valavala et al., 2011). To prevent such drawbacks to the process, conventional as well as non-conventional pretreatment methods have been used, namely coagulation- flocculation, sedimentation, granular media filtration, dissolved air flotation, ultrafiltration, microfiltration, and nanofiltration (Prihasto et al., 2009; Valavala et al., 2011). Within this context, precipitation softening is a conventional pretreatment process that contributes to the removal of a number of scale-producing and fouling pollutants, such as magnesium, calcium, silica, and strontium. The proposed research aims at assessing the effectiveness of precipitation softening as a pretreatment process for brackish water reverse osmosis. This was achieved by selecting the optimal softening chemicals and dosages, followed by examining the removal efficiency of a number of scaling and fouling contaminants under differen