The textile industry has long been associated with significant environmental challenges due to the generation of recalcitrant wastewater, containing complex chemical mixture that pose severe threats to ecosystems and human health. This study focuses on the role of pH adjustment in improving the pretreatment process for direct contact membrane distillation (DCMD) applied to real textile wastewater. By implementing a pH adjustment step (pH 6.14, 7.40, and 9.06) prior to sedimentation and filtration, the pretreatment process was significantly enhanced, reducing wetting, and improving permeate quality. GC–MS analysis identified specific organic molecules causing wetting, including volatile organic acids and alcohol derivatives, revealing that the rejection mechanism is primarily driven by the relationship between the wastewater pH and the pKa of these compounds. Adjusting the pH above the pKa converts these acidic contaminants into ionic, non-volatile forms, effectively preventing their passage into the permeate. This study highlights the importance of pH optimization in advancing DCMD as a sustainable solution for textile wastewater treatment. The proposed approach aligns with circular economy principles, enabling water reuse in textile processes, reducing freshwater consumption, and minimizing environmental discharge.

This case study investigated the effectiveness of Direct Contact Membrane Distillation (DCMD) in treating real textile wastewater. Textile wastewater treatment presents a critical challenge in the field of environmental sustainability, requiring innovative approaches for its treatment to mitigate adverse impacts on ecosystems. DCMD emerges as a promising solution for the treatment and reuse of textile wastewater. However, the intricate composition of real textile wastewater represents a major bottleneck for the process, as the effectiveness of DCMD is influenced by numerous factors, complicating its application. In this study, experiments with an untreated sample demonstrate the detrimental impact of suspended solids on membrane performance. The application of simple pretreatment steps prior to DCMD, involving sedimentation and filtration, substantially enhanced the quality of the permeate, resulting in 100 % color removal, 99.99 % turbidity removal, and considerable removal rates for Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC). Nevertheless, wetting remained a significant issue, as evidenced by the persistence of commonly used volatile organic contaminants and surfactants in the textile industry detected within the permeate. The findings in this case study reinforce that DCMD holds promise for textile wastewater treatment but emphasize the necessity of pretreatment and wetting mitigation strategies to fully unlock its potential. This research offers crucial insights for future MD applications in addressing the complexities of textile wastewater treatment.

This study describes a novel integration of aerobic granular sludge (AGS) with a gravity-driven membrane (GDM) system at a pilot scale with a treatment capacity of approximately 150 L per day to treat raw domestic wastewater. The treatment performance and energy consumption of the AGS-GDM system were compared to the neighboring full-scale aerobic membrane bioreactor (AeMBR), treating the same wastewater at about 4000(±500) m³ per day. The AGS-GDM system demonstrated superior nutrient (nitrogen and phosphorus) removal as compared to the AeMBR. The GDM unit was continuously supplied with AGS-treated effluent. The GDM unit started with high [ >20 L per m² per h (LMH) ] flux, which gradually declined. The flux remained quite stable after 15 days reaching 3 LMH after 35 days without any physical or chemical cleaning. Our results suggest that AGS-GDM is a viable technology for decentralized wastewater treatment and reuse in water-scarce regions. The AGS-GDM could easily replace conventional AeMBR technology in the wastewater treatment and reclamation market.

The use of optical coherence tomography (OCT) to investigate biomass in membrane systems has increased with time. OCT is able to characterize the biomass in-situ and non-destructively. In this study, a novel approach to process three-dimensional (3D) OCT scans is proposed. The approach allows obtaining spatially-resolved detailed structural biomass information. The 3D biomass reconstruction enables analysis of the biomass only, obtained by subtracting the time zero scan to all images. A 3D time series analysis of biomass development in a spacer filled channel under representative conditions (cross flow velocity) for a spiral wound membrane element was performed. The flow cell was operated for five days with monitoring of ultrafiltration membrane performance: feed channel pressure drop and permeate flux. The biomass development in the flow cell was detected by OCT before a performance decline was observed. Feed channel pressure drop continuously increased with increasing biomass volume, while flux decline was mainly affected in the initial phase of biomass accumulation. The novel OCT imaging approach enabled the assessment of spatial biomass distribution in the flow cell, discriminating the total biomass volume between the membrane, feed spacer and glass window. Biomass accumulation was stronger on the feed spacer during the early stage of biofouling, impacting the feed channel pressure drop stronger than permeate flux.

Aquaporin plays a promising role in fabricating high performance biomimetic forward osmosis (FO) membranes. However, aquaporin as a protein also has a risk of denaturation caused by various chemicals, resulting in a possible decay of membrane performance. The present study tested a novel aquaporin based biomimetic membrane in simulated membrane cleaning processes. The effects of cleaning agents on water flux and salt rejection were evaluated. The membrane showed a good resistance to the chemical agents. The water flux after chemical cleaning showed significant increases, particularly after cleaning with NaOCl and Alconox. Changes in the membrane structure and increased hydrophilicity in the surrounding areas of the aquaporin may be accountable for the increase in water permeability. The membrane shows stable salt rejection up to 99% after all cleaning agents were tested. A 15-day experiment with secondary wastewater effluent as the feed solution and seawater as the draw solution showed a stable flux and high salt rejection. The average rejection of the dissolved organic carbon from wastewater after the 15-day test was 90%. The results demonstrated that the aquaporin based biomimetic FO membrane exhibits chemical resistance for most agents used in membrane cleaning procedures, maintaining a stable flux and high salt rejection.