Effective pretreatment is essential for achieving long-term stable operation and high water recovery during the desalination of alternative waters. This study developed a process modeling approach for technical, economic, energetic, and environmental assessments of pretreatment technologies to identify the impacts of each technology treating brackish water desalination brine with high scaling propensity. The model simulations evaluated individual pretreatment technologies, including chemical softening (CS), chemical coagulation (CC), electrocoagulation (EC), and ion exchange (IX). In addition, combinations of these pretreatment technologies aiming at the effective reduction of key scaling constituents such as hardness and silica were investigated. The three evaluation parameters in this assessment consist of levelized cost of water (LCOW, $/m³), specific energy consumption and cumulative energy demand (SEC|CED, kWh/m³), and carbon dioxide emissions (CO₂, kg CO_2-eq/m³). The case study evaluated in this work was the desalination brine from the Kay Bailey Hutchison Desalination Plant (KBHDP) with a total dissolved solids (TDS) concentration of 11,000 mg/L and rich in hardness and silica. The evaluation of individual pretreatment units from the highest to lowest LCOW, SEC|CED, and CO₂ emissions in the KBHDP brine was IX > CS > EC > CC, CS > IX > EC > CC, and CC > CS > EC > IX, respectively. In the case of pretreatment combinations for the KBHDP, the EC + IX treatment combination was shown to be the best in terms of the LCOW and CO₂ emissions. The modeling and evaluation of these pretreatment units provide valuable guidance on the selection of cost-effective, energy-efficient, and environmentally sustainable pretreatment technologies tailored to desalination brine applications for minimal- or zero-liquid discharge.

Membrane treatment of secondary effluent for reuse applications is a promising approach to expand water supplies and provide flexibility to water resources management. However, effective control of membrane fouling and scaling is crucial for cost-effective treatment and system resilience. This study compared the performance of antiscalants to an alternating, current-induced electromagnetic field (EMF) as an alternative pretreatment method to reverse osmosis. Compared to the no-EMF control experiments, the EMF device resulted in 13% higher water recovery and 366% lower flux decline at 60% of water recovery, along with 2–8 times lower precipitation of fouling and scaling, as evidenced by scanning electron microscope, energy dispersive X-ray spectroscopy, and chemical extraction analysis. The combination of the EMF with antiscalant was more effective for reducing membrane fouling and scaling, increasing water recoveries up to 89.3%, as compared to the EMF (67.5%) and antiscalant-only (73.6%) configurations. This is the first study to demonstrate synergistic effects of using an EMF in combination with antiscalants and could lead to lower pretreatment costs. Additional research is required to quantify the economics of this approach and to fully understand the fundamental mechanisms governing fouling and scaling control by an EMF.

Reverse osmosis concentrate (ROC) treatment is critical for enhancing water recovery and minimizing concentrate volume for disposal, especially in regions facing water scarcity. This study investigates the application of ion exchange (IX) resins and activated alumina (AA) as pretreatment strategies to mitigate scaling in ROC due to high concentrations of total dissolved solids, hardness (Ca²⁺ and Mg²⁺), and silica. Through a series of Langmuir isotherms, continuous column experiments, and model simulation, two types of strong acid cation IX resins and three types of strong base anion IX resins alongside three types of AA were evaluated. Results indicate that AA exhibits superior performance in silica removal, achieving up to a 65% reduction and maintaining performance for up to 800 bed volume without reaching saturation. Model simulation of a secondary reverse osmosis treating ROC after the IX and AA pretreatment indicated an additional water recovery of ~70% using antiscalants. This study demonstrates the potential for achieving higher water recovery while also identifying opportunities for pretreatment improvement. Challenges such as the limited IX capacity treating ROC, which requires frequent regeneration and increases operational costs, along with the restricted regeneration capacity of AA, underscore the importance of innovation. These findings emphasize the critical need for developing advanced materials and optimized strategies to further enhance the efficiency of ROC treatment processes.

Reverse osmosis concentrate (ROC) treatment is critical for enhancing water recovery, especially in regions facing water scarcity. The high concentrations of total dissolved solids (TDS), hardness (Ca2+ and Mg2+) and silica, present significant challenges for ROC treatment due to their high scaling potential. Developing effective pretreatment strategies, such as ion exchange (IX) and activated alumina (AA), to mitigate scaling is essential for improving water recovery. This study investigates the effectiveness of dif-ferent ion exchange (IX) resins and activated alumina (AA) in removing hardness and silica from brackish water ROC, through batch isotherm studies, continuous column experiments, regeneration, impact of operating conditions, model simulation, and pre-liminary costs analysis. The ROC is characterized by TDS 12,445 mg/L, Ca²⁺ 847 mg/L, Mg²⁺ 212 mg/L, and silica 160 mg/L. Hardness removal was evaluated using two types of strong acid cation (SAC) IX resins and silica removal using three types of strong base anion (SBA) IX resins and three types of AA. While IX was effective in removing hardness and silica during the initial stages of column experiments, hardness breakthrough occurred at 17–33 bed volumes (BV) for SAC and 5 BV for silica using SBA, due to their high con-centrations in ROC. In contrast, AA demonstrated superior and sustained silica removal, reducing silica concentration in ROC by up to 65% and maintaining performance for up to 800 BV without reaching saturation. Model simulation of a secondary RO treating ROC after the IX and AA pretreatment indicated an additional water recovery of ~70% using antiscalants. While this study demonstrates the potential for achieving higher water recovery, significant challenges remain, including limited capacity of IX resins for ROC treatment, which necessitates frequent regeneration and adds operational costs, as well as the restricted regeneration capacity of AA. These findings emphasize the critical need for developing advanced materials and optimized strategies to enhance the efficiency of ROC treatment processes.