Effect of organic micropollutants on biofouling in a forward osmosis process integrating seawater desalination and wastewater reclamation

Synergistic effects of microplastics and organic foulants on the performance of forward osmosis membranes

Microplastics (MPs) are emerging contaminants that are abundantly present in the influent and effluent of wastewater treatment plants (WWTPs). Forward osmosis (FO) is an advanced treatment technology with potential applications in WWTPs. The presence of MPs in WWTP effluents can contribute to FO fouling and performance deterioration. This study focuses on FO membrane fouling by MPs of different sizes, and the interactional impacts of MPs and Humic acid (HA) (as the most common organic foulant in WWTPs) on FO membrane performance. The synergistic effect of combined MPs and HA fouling is shown to cause higher flux decline for FO membranes than that of HA or MPs alone. Reverse salt flux increased in the presence of MPs, and decreased when HA was present. Further, full flux recovery was obtained for all fouled membranes after hydraulic cleaning. This indicates the efficiency of FO systems for treating wastewater with high fouling potential. This study highlights the necessity of considering MPs in studying fouling behaviour, and for mitigation strategies of membranes used in WWT. The fundamentals created here can be further extended to other membrane-assisted separation processes.

Sunlight-active phytol-ZnO@TiO2 nanocomposite for photocatalytic water remediation and bacterial-fouling control in aquaculture: A comprehensive study on safety-level assessment

With a growing consciousness of the importance of nature stewardship, researchers are focusing their efforts on utilizing renewable energy, particularly solar energy, to address environmental concerns. In this context, photocatalysis has long been viewed as one of the most promising cleaning methods. Hence, we have prepared a sunlight-active phytol-assisted ZnO-TiO₂ nanocomposite (PZTN) for photocatalytic bacterial deactivation and dye degradation process. The PZTN-photocatalysis effectively deactivated the bacterial pathogens as well as malachite green dye within 240 min under direct-sunlight. Moreover, this will be the first complete study on safety level assessment of photocatalytically-remediated water through toxicity studies. The obtained results evidenced that photocatalytically-deactivated bacteria and MG-dye showed to have no toxic effects, signifying that the PZTN-photocatalyzed water seems to be extremely safe for the environment. As a result of this research, we suggest that the PZTN could be a promising sunlight-active photocatalyst for environmental water treatment. On the other hand, biofouling is a ubiquitous phenomenon in the marine environment. Bacteria are the first organisms to foul surfaces and produce biofilms on man-made submerged materials. Interestingly, PZTN-coated PVC plastic-films effectively disallowed biofilms on their surface. This part of this research suggests that PZTN coated PVC-plastics are the best alternative for biofouling management.

Towards sustainable circular brine reclamation using seawater reverse osmosis, membrane distillation and forward osmosis hybrids: An experimental investigation

Desalination and wastewater treatment technologies require an effective solution for brine management to ensure environmental sustainability, which is closely linked with efficient process operations, reduction of chemical dosages, and valorization of brines. Within the scope of desalination brine reclamation, a circular system consisting of seawater reverse osmosis (SWRO), membrane distillation (MD), and forward osmosis (FO) three-process hybrid is investigated. The proposed design increases water recovery from SWRO brine (by MD) and dilutes concentrated brine to seawater level (by FO) for SWRO feed. It ultimately reduces SWRO process brine disposal and improves crystallization efficiency for a zero-liquid discharge application. The operating range of the hybrid system is indicated by a seawater volumetric concentration factor (VCF) ranging from 1.0 to 2.2, which covers practical and sustainable operation in full-scale applications. Within the proposed VCF range, different operating conditions of the MD and FO processes were evaluated in series with concentrated seawater as well as real SWRO brine from a full-scale desalination plant. Water quality and membrane surface were analyzed before and after experiments to assess the impact of the SWRO brine. Despite their low concentration (0.13 mg/L as phosphorous), antiscalants present in SWRO brine alleviated the flux decline in MD operations by 68.3% compared to operations using seawater concentrate, while no significant influence was observed on the FO process. A full spectrum of water quality analysis of real SWRO brine and Red Sea water is made available for future SWRO brine reclamation studies. The operating conditions and experimental results have shown the potential of the SWRO-MD-FO hybrid system for a circular brine reclamation.