Forward osmosis for industrial effluents treatment – sustainability considerations

A review on existing and emerging approaches for textile wastewater treatments: challenges and future perspectives

This comprehensive review explores the complex environment of textile wastewater treatment technologies, highlighting both well-established and emerging techniques. Textile wastewater poses a significant environmental challenge, containing diverse contaminants and chemicals. The review presents a detailed examination of conventional treatments such as coagulation, flocculation, and biological processes, highlighting their effectiveness and limitations. In textile industry, various textile operations such as sizing, de-sizing, dyeing, bleaching, and mercerization consume large quantities of water generating effluent high in color, chemical oxygen demand, and solids. The dyes, mordants, and variety of other chemicals used in textile processing lead to effluent variable in characteristics. Furthermore, it explores innovative and emerging techniques, including advanced oxidation processes, membrane filtration, and nanotechnology-based solutions. Future perspectives in textile wastewater treatment are discussed in-depth, emphasizing the importance of interdisciplinary research, technological advancements, and the integration of circular economy principles. Numerous dyes used in the textile industry have been shown to have mutagenic, cytotoxic, and ecotoxic potential in studies. Therefore, it is necessary to assess the methods used to remediate textile waste water. Major topics including the chemical composition of textile waste water, the chemistry of the dye molecules, the selection of a treatment technique, the benefits and drawbacks of the various treatment options, and the cost of operation are also addressed. Overall, this review offers a valuable resource for researchers and industry professionals working in the textile industry, pointing towards a more sustainable and environmentally responsible future.

Biofouling mechanism and cleaning procedures for Spirulina platensis as an organic fertilizer draw solution

The forward osmosis (FO) desalination process has recently acknowledged a lot of attention as a promising solution for reducing the disadvantages of existing desalination systems. This work aimed to investigate the effect of a selected liquid organic fertilizer a novel draw solution produced from "microalgae Spirulina platensis" on the biofouling mechanism of FO membrane. Different draw solution (DS) concentrations ranging 240-480 g/L were examined, obtained water flux ranging from 6.5 to 3.4 Lm2h-1. A high flux decline was observed when using higher DS concentrations due to fouling layer accumulated throughout the membrane area which lowers the effective osmotic pressure difference. Different cleaning strategies were examined. The biofouled membrane was cleaned on-line with deionized water (DI) and externally using ultrasound (US) and HCl. Baseline experiments were done to investigate the efficiency of the cleaning strategies. After cleaning using the deionized water (DI) water, it was found that the water flux progressed from 3.4 to 7 Lm2h-1, while when using acid cleaning the flux recovered to 15 Lm-2h-1. The efficacy and amount of foulant removed by each cleaning stage were assessed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

Optimization and prediction of lead removal from aqueous solution using FO-MD hybrid process: Statistical and artificial intelligence analysis

Heavy metals (HMs) has become one of the most serious pollutants that are harmful to the environment and ecology. This paper focused on the removal of lead contaminant from wastewater by forward osmosis-membrane distillation (FO-MD) hybrid process using seawater as draw solution. Modeling, optimization, and prediction of FO performance are developed using complementary approach based on response surface methodology (RSM) and an artificial neural network (ANN). FO process optimization using RSM revealed that under initial lead concentration of 60 mg/L, feed velocity of 11.57 cm/s and draw velocity of 7.66 cm/s, FO process achieved highest water flux of 6.75 LMH, lowest reverse salt flux of 2.78 gMH and highest lead removal efficiency of 87.07%. Fitness of all models was evaluated based on determination coefficient (R²) and mean square error (MSE). Results showed highest R² value up to 0.9906 and lowest RMSE value up to 0.0102. ANN modeling generates the highest prediction accuracy for water flux and reverse salt flux, while RSM produces the highest prediction accuracy for lead removal efficiency. Subsequently, FO optimal conditions are applied on FO-MD hybrid process using seawater as draw solution and evaluate their performance to simultaneously remove lead contaminant and desalination of seawater. Results displays that FO-MD process shows a highly efficient solution to produce fresh water with almost free heavy metals and very low conductivity.

Simultaneous phosphorus recovery from wastewater and sludge by a novel denitrifying phosphorus removal system

A novel process was proposed for simultaneous denitrification and phosphorus (P) recovery. The increased nitrate concentration facilitated the activity of denitrifying P removal (DPR) in P enrichment, which stimulated P uptake and storage, making P more readily accessible for release into the recirculated stream. The total P content in the biofilm (TP_biofilm) rose to 54.6 ± 3.5 mg/g SS as the nitrate concentration increased from 15.0 to 25.0 mg/L, while the P concentration of the enriched stream reached 172.5 ± 3.5 mg/L. Moreover, the abundance of denitrifying polyphosphate accumulating organisms (DPAOs) increased from 5.6% to 28.0%, and the increased nitrate concentration facilitated the process of carbon, nitrogen, and P metabolism due to the rise in the genes involved in critical functions of metabolism. Acid/alkaline fermentation analysis indicated that the EPS release was the primary P-release pathway. Additionally, pure struvite crystals were obtained from the enriched stream and fermentation supernatant.

Forward Osmosis for Metal Processing Effluents under Similar Osmotic Pressure Gradients

Water recovery from aqueous effluents in the mining and metals processing industry poses a unique challenge due to the high concentration of dissolved salts typically requiring energy intensive methods of treatment. Forward osmosis (FO) is a lower energy technology which employs a draw solution to osmotically extract water through a semi-permeable membrane further concentrating any feed. Successful FO operation relies on using a draw solution of higher osmotic pressure than the feed to extract water while minimizing concentration polarization to maximize the water flux. Previous studies employing FO on industrial feed samples commonly used concentration instead of osmotic pressures for feed and draw characterization; this led to misleading conclusions on the impact of design variables on water flux performance. By employing a factorial design of experiments methodology, this study examined the independent and interactive effects on water flux by: osmotic pressure gradient, crossflow velocity, draw salt type, and membrane orientation. With a commercial FO membrane, this work tested a solvent extraction raffinate and a mine water effluent sample to demonstrate application significance. By optimizing with osmotic gradient independent variables, water flux can be improved by over 30% without increasing energy costs or compromising the 95-99% salt rejection of the membrane.

Design, synthesis, and application of thermally responsive draw solutes for sustainable forward osmosis desalination: A review

Forward osmosis (FO) is an emerging sustainable desalination technology; however, it is not a stand-alone process and requires an additional step to recover the water or regenerate the draw solute (DS), making it energy extensive. Therefore, incorporating inexpensive energy sources for DS regeneration is a viable solution to compete with reverse osmosis desalination technology. Hence, selecting suitable DS and its regeneration became a crucial research focus in FO desalination. Among various DSs reported, thermally responsive DSs (TRDS) provide an opportunity to integrate low-grade energy sources for DS regeneration. Utilizing such inexpensive energy will reduce fossil fuel energy demand, lower the cost of desalination, and minimize the carbon footprint. Hence, this review explores the TRDS for FO-based desalination with its design, synthesis, and applications. The manuscript has discussed the classification and selection criteria for the DSs, and how traditional and new-generation TRDSs are designed and synthesized from cationic and anionic moieties of ionic liquids, hydrogels, and other chemicals. The manuscript has also given importance to design criteria such as osmotic strength, viscosity, toxicity, and thermal stability for TRDSs. Furthermore, a detailed discussion on the FO performance, energy, and economic aspects of TRDSs has been reviewed, along with a discussion on the possible low-grade energy sources for the recovery of TRDS. Finally, the challenges and future directions for TRDSs have been discussed to drive FO toward sustainable desalination technology.

Thermoresponsive Ionic Liquid with Different Cation-Anion Pairs as Draw Solutes in Forward Osmosis

We synthesized various phosphonium- and ammonium-based ionic liquids (ILs), using benzenesulfonate (BS) and 4-methylbenzenesulfonate (MBS) to establish the criteria for designing an ideal draw solute in a forward osmosis (FO) system. Additionally, the effects of monocationic, dicationic, and anionic species on FO performance were studied. Monocationic compounds ([P₄₄₄₄][BS], [P₄₄₄₄][MBS], [N₄₄₄₄][BS], and [N₄₄₄₄][MBS]) were obtained in one step via anion exchange. Dicationic compounds ([(P₄₄₄₄)₂][BS], [(P₄₄₄₄)₂][MBS], [(N₄₄₄₄)₂][BS], and [(N₄₄₄₄)₂][MBS]) were prepared in two steps via a Menshutkin SN₂ reaction and anion exchange. We also investigated the suitability of ILs as draw solutes for FO systems. The aqueous [P₄₄₄₄][BS], [N₄₄₄₄][BS], [N₄₄₄₄][MBS], and [(N₄₄₄₄)₂][BS] solutions did not exhibit thermoresponsive behavior. However, 20 wt% [P₄₄₄₄][MBS], [(P₄₄₄₄)₂][BS], [(P₄₄₄₄)₂][MBS], and [(N₄₄₄₄)₂][MBS] had critical temperatures of approximately 43, 33, 22, and 60 °C, respectively, enabling their recovery using temperature. An increase in IL hydrophobicity and bulkiness reduces its miscibility with water, demonstrating that it can be used to tune its thermoresponsive properties. Moreover, the FO performance of 20 wt% aqueous [(P₄₄₄₄)₂][MBS] solution was tested for water flux and found to be approximately 10.58 LMH with the active layer facing the draw solution mode and 9.40 LMH with the active layer facing the feed solution.

Recent advances in the removal of dyes from wastewater using low-cost adsorbents

The presence of hazardous dyes in wastewater cause disastrous effects on living organisms and the environment. The conventional technologies for the remediation of dyes from water have several bottlenecks such as high cost and complex operation. This review aims to present a comprehensive outlook of various bio-sorbents that are identified and successfully employed for the removal of dyes from aqueous environments. The effect of physicochemical characteristics of adsorbents such as surface functional groups, pore size distribution and surface areas are critically evaluated. The adsorption potential at different experimental conditions of diverse bio-sorbents has been also explored and the influence of certain key parameters like solution pH, temperature, concentration of dyes, dosage of bio-sorbent and agitation speed is carefully evaluated. The mechanism of dyes adsorption, regeneration potential of the employed bio-sorbents and their comparison with other commercial adsorbents are discussed. The cost comparison of different adsorbents and key technological challenges are highlighted followed by the recommendations for future research.

Comammox bacteria predominate among ammonia-oxidizing microorganisms in municipal but not in refinery wastewater treatment plants

Comammox bacteria have proved to be one dominant and significant ammonia-oxidizing microorganisms (AOMs) in municipal wastewater treatment plants (WWTPs), however, it still remains unknown about their abundance and diversity in industrial WWTPs. In this study, activated sludge samples from 8 municipal WWTPs and 6 industrial WWTPs treating refinery wastewater were taken and analyzed using qPCR and amoA gene sequencing. Intriguingly, quantitative real-time PCR (qPCR) results suggested that comammox bacteria had a higher numerical abundance compared with ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in municipal WWTPs but did not in refinery WWTPs. Moreover, comammox amoA sequences obtained from high-throughput sequencing were retrieved from all the 8 municipal samples but only 1 industrial sample. Further phylogenetic analysis revealed that N. nitrosa cluster accounted for as high as 79.56% of the total comammox affiliated sequences, which was the most numerically abundant comammox species in municipal WWTPs. This study provided new insights into the abundance and diversity of comammox bacteria in the biological nitrification process in municipal and refinery wastewater treatment systems.

Efficient removal of heavy metal ions from aqueous media by unmodified and modified nanodiamonds

This article deals with the adsorption performances of the unmodified nanodiamond (ND) and thermally oxidized nanodiamond (Ox-ND) for the removal of different heavy metal ions such as Fe (III), Cu (II), Cr (VI), and Cd (II) from wastewater. The adsorption capacities of the ions onto adsorbents are higher and follow the order: Ox-ND-3 > Ox-ND-1.5 > ND, which is consistent with their surface areas, zeta potentials, and the presence of carboxyl groups, suggesting that electrostatic attractions between the positive metal ions and the negatively charged adsorbents are the predominant adsorption mechanisms. Adsorption capacities of these adsorbents were found to be 26.8, 31.3, and 45.7 mg/g for Fe (III), 25.2, 30.5, and 44.5 mg/g for Cu (II), 33.6, 44.1, and 55.9 mg/g for Cr (VI), and 40.9, 52.9, and 67.9 mg/g for Cd (II) over ND, Ox-ND-1.5, and Ox-ND-3, respectively. The impact of various operating parameters such as agitation time, initial metal ion concentration, temperature, pH solution, adsorbent dosage, and coexistence of the metal ions on the adsorption performance of Ox-ND-3 towards Cd (II) ions along with the batch adsorption experiments were performed. The equilibrium was reached in 120 min and adsorption data were fitted well with the pseudo-second-order kinetic as well as the Freundlich isotherm models. Adsorption process was spontaneous and exothermic, while the maximum removal efficiency of Cd (II) ions occurred at pH of 6.9 and at 4 g/L dosage. These findings demonstrated that thermally oxidized nanodiamond (Ox-ND) can be a versatile adsorbent to remove the Cd (II) ions from wastewater.

Protein nanofibrils as versatile and sustainable adsorbents for an effective removal of heavy metals from wastewater: A review

Water is a valuable natural resource, which plays a crucial role in ecological survival as well as economic progress. However, the water quality has deteriorated in recent years as a result of urbanization, industrialization and human activities due to the uncontrolled release of industrial wastes, which can be extremely carcinogenic and non-degradable, in air, water and soil bodies. Such wastes showed the presence of organic and inorganic pollutants in high dosages. Heavy metals are the most obstinate contaminants, and they can be harmful because of having a variety of detrimental consequences to the ecosystem. The existing water treatment methods in many situations may not be sustainable or effective because of their high energy requirements and ecological impacts. In this review, state-of-the-art water treatment methods for the elimination of heavy metals with the help of protein nanofibrils are covered featuring a discussion on the strategies and possibilities of developing protein nanofibrils for the active elimination of heavy metals using kitchen waste as well as residues from the cattle, agriculture, and dairy industries. Further, the emphasis has been given to their environmental sustainability and economical aspects are also discussed.

Desalination of Municipal Wastewater Using Forward Osmosis

Membrane technology has gained much ground in water and wastewater treatment over the past couple of decades. This is timely, as the world explores smart, eco-friendly, and cheap water and wastewater treatment technologies in its quest to make potable water and sanitation commonplace in all parts of the world. Against this background, this study investigated forward osmosis (FO) in the removal of salts (chlorides, sulphates, and carbonates) and organics (chemical oxygen demand (COD), turbidity, total suspended solids (TSS), and color) from a synthetic municipal wastewater (MWW), mimicking secondary-treated industrial wastewater, at very low feed and draw solution flow rates (0.16 and 0.14 L/min respectively), using 70 g/L NaCl solution as the draw solution. The results obtained showed an average of 97.67% rejection of SO₄²⁻ and CO₃²⁻ while Cl⁻ was found to enrich the feed solution (FS). An average removal of 88.92% was achieved for the organics. A permeation flux of 5.06 L/m².h was obtained. The kinetics of the ions transport was studied, and was found to fit the second-order kinetic model, with Pearson’s R-values of 0.998 and 0.974 for Cl⁻ and CO₃²⁻ respectively. The study proves FO as a potential technology to desalinate saline MWW.