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.

Reverse osmosis (RO) desalination is the leading technology for industrial and municipal water production in water-stressed regions. While developing chemical-free scaling control strategies helps mitigate the environmental impact of brine discharge, it also increases the risk of membrane scaling due to high salt concentrations. Establishing methods for early detection and localization of scaling is essential, as well as understanding the impact on key operational parameters. This study evaluated optical coherence tomography (OCT) for real-time monitoring of growth- and deposition-driven gypsum fouling in RO systems. Membrane fouling simulators were operated under constant flux conditions using unsaturated and supersaturated synthetic water solutions. Real-time monitoring of operational parameters revealed that growth and deposition fouling had a greater impact on transmembrane pressure than pressure drop increase. OCT imaging visualized scaling progression, with optical and SEM imaging confirming distinct morphologies: sharp, translucent crystals in growth-driven scaling and a white, amorphous fouling layer in deposition. Data processing further provided quantitative assessment of area coverage and fouling volume, with membrane autopsy indicating higher porosity in the deposition case. Crystal detection from OCT imaging evidenced sensitivity for early-stage scaling detection. In the growth case, a strong correlation was observed between initial crystal formation and regions of maximum saturation index, as revealed by CFD with multicomponent solute transport simulations. The variation in induction time across detection methods highlights the importance of sensitivity of monitoring techniques, positioning OCT as a valuable tool for early scaling detection, before conventional indicators point out to significant scaling.

In this study, the efficiency of electrocoagulation (EC) with iron electrodes was applied to remove two phosphonates, 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP) and nitrilotris(methylene) triphosphonic acid (NTMP) from concentrates. This work provides a detailed description of the experimental procedure and results on phosphonate removal and recovery from different electrolytes, including synthetic and real reverse osmosis (RO) membrane concentrates. This research showed high selectivity of EC, removing 100% and 80% of the NTMP and the HEDP respectively, confirming no competition with sulfates, nitrates, or silica. When experimenting with other electrolytes, calcium showed to be critical in enhancing the flocculation process, while calcium carbonate precipitation contributed to capturing the phosphonates from the concentrate. The produced iron oxide (sludge) was confirmed as goethite and akaganéite, and finally transformed into hematite, indicating the oxidation from Fe2+ to Fe3+ during the EC process. After the iron precipitate collection, an alkaline wash of the sludge was enough to recover 100% of the initial phosphorus from the NTMP phosphonate. However, further research is needed to optimize the recovery procedure and to improve the results with the HEDP. 70 and 140 A·m-2 current densities were optimal to bring HEDP and NTMP concentrations down to 32 μM (1 mg·L-1) in only 30 and 10 min respectively. In these conditions, the operational costs, 1.10 and 0.03 €·m-3 of treated concentrate, were estimated for HEDP and NTMP respectively. Even when EC has been widely studied for phosphate removal, this technique has been barely applied to treat concentrates containing phosphonate-based antiscalants. EC opens new possibilities for phosphonates and phosphorus to be removed and recovered respectively from membrane and other concentrates.

Natural Deep Eutectic Solvents (NADES) are composed of supramolecular interactions of two or more natural compounds, such as organic acids, sugars, and amino acids, and they are being used as a new media alternative to conventional solvents. In this study, a new application of NADES is presented as a possible technology for biofilm structural breaker in complex systems since the current solvents used for biofilm cleaning and extraction of biofilm components use hazardous solutions. The NADES (betaine:urea:water and lactic acid:glucose:water) were analyzed before and after the biofilm treatment by attenuated total reflection Fourier-transform infrared spectroscopy and fluorescence excitation-emission matrix spectroscopy. Our results indicate that the green solvents could solubilize up to ≈70 percent of the main components of the biofilms extracellular matrix. The solubilization of the biomolecules weakened the biofilm structure, which could enhance the biofilm solubilization and removal. The NADES have the potential to be an environment-friendly, green solvent to extract valuable compounds and break the main structure from the biofilm, leading to a greener method for extracellular polymeric substance (EPS) extraction and biofilm treatment in various water treatment systems.