Evaluation of the hybrid system combining electrocoagulation, nanofiltration and reverse osmosis for biologically treated textile effluent: Treatment efficiency and membrane fouling

Enhancing textile wastewater reuse: Integrating Fenton oxidation with membrane filtration

The textile industry produces large volumes of wastewater with complex organic pollutants, dyes, and chemicals that are challenging to treat. This study introduces an integrated approach combining Fenton oxidation and membrane filtration in a continuous flow system to improve textile wastewater treatment. The study optimized the removal efficiencies of COD, TOC, and colour by varying the dosages of Fe2+ and H2O2, as well as adjusting the pH and flow rates. Optimal conditions were pH 3.0, 3 mM Fe2+, 10 mM H2O2, and a flow rate of 25 mL/min for both Fenton and photo-Fenton processes. Artificial Neural Networks (ANNs) were employed to simulate and forecast treatment outcomes, identifying reaction time as the most critical factor with relative importance values of 57% for COD and 55% for TOC in Fenton oxidation, and 57% for COD and 49% for TOC in photo-Fenton oxidation. The optimized Fenton process was integrated with microfiltration (MF) and reverse osmosis (RO), to enable the recycling and reuse of wastewater. In the integrated system, COD and TOC removal efficiencies reached 96% and 95%, respectively, following the RO process. Prior to this, after Fenton oxidation, sedimentation, and sand filtration, the COD and TOC removal efficiencies were 70% and 73%, respectively. Colour removal efficiency was 98% after Fenton oxidation, and complete removal was achieved after membrane filtration. The system also significantly reduced electrical conductivity (EC) and concentrations of chloride, sulphate, calcium, and sodium, making the water suitable for reuse. Additionally, the study addressed membrane fouling and proposed strategies to improve long-term operational efficiency. This integrated approach offers a scalable and effective solution for textile wastewater treatment, supporting environmental sustainability and resource conservation.

Recent progress in highly effective electrocoagulation-coupled systems for advanced wastewater treatment

Electrocoagulation (EC) has been a well-known technology for wastewater treatment over the past centuries, owing to its straightforward equipment requirements and highly effective contaminant removal efficiency. This literature review emphasizes the influence of several input variables in the EC system such as electrode materials, applied current, pH, supporting electrolyte, and inner-electrode distance on effluent removal efficiency and energy consumption. Besides that, depending on the intrinsic properties of effluents, EC is recommended to hybridize with other methods such as physical-, biological-, chemical-, and electrochemical methods in order to enhance removal performance and reduce energy consumption. Subsequently, a comprehensive analysis of EC performance is presented, including power consumption, and evaluation of the synergistic effect of multiple input variables using statistical methods. Finally, this review discusses future perspectives such as the environmentally friendly utilization of post-EC treated sludges, the development of renewable energy-driven EC systems, and the challenges of EC management by artificial intelligence.

Reverse Osmosis Coupled with Ozonation for Clean Water Recovery from an Industrial Effluent: Technical and Economic Analyses

Technical and economic criteria were used to evaluate the feasibility of the treatment of an industrial effluent (10 m3/h) for water recovery and reuse. The treatment evaluation included the following: (1) effluent characteristic determination; (2) selection and evaluation of the effluent treatment at lab scale, establishing operating conditions and process efficiency; (3) scaling up the treatment process to the industrial level; (4) treatment plant design and commercial availability analysis of the required equipment; and (5) the costs of the inversion and operation of the plant treatment, cost/m3 for water recovery, and time of investment recovery. The physicochemical characteristics of the effluent exposed the polluted wastewater with sodium chloride salts and colourants, predominating a mixture of tartrazine, Red 40, and brilliant blue from the synthesis of food additives. Other contributions of organic compounds and salts could be in minor content. According to the effluent conditions, a coupled process, integrated with ozonation and reverse osmosis, was indicated to be a treatment for water recovery. Scaling up the plant treatment design resulted in 130 m2 of area, producing 7.7 m3/h of clean water. The cost of the effluent treatment was 1.4 USD/m3, with an inversion return of 3.4 years and cost investment of USD 860,407. The treatment process resulted a viable project for water recovery.

High-efficiency removal of As(iii) from groundwater using siderite as the iron source in the electrocoagulation process

Electrocoagulation technology, due to its simplicity and ease of operation, is often considered for treating arsenic-contaminated groundwater. However, challenges such as anode wear have hindered its development and application. This study aims to develop a siderite-filled anode electrocoagulation system for efficient removal of As(iii) and investigate its effectiveness. The impact of operational parameters on the removal rate of As(iii) was analyzed through single-factor tests, and the stability and superiority of the device were evaluated. The response surface methodology was employed to analyze the interactions between various factors and determine the optimal operational parameters by integrating data from these tests. Under conditions where the removal rate of As reached 99.3 ± 0.37%, with an initial concentration of As(iii) at 400 μg L-1, current intensity at 30 mA, initial solution pH value at 7, and Na2SO4 concentration at 10 mM. The flocculant used was subjected to characterization analysis to examine its structure, morphology, and elemental composition under these optimal operational parameters. The oxidation pathway for As(iii) within this system relies on integrated results from direct electrolysis as well as ˙O2 -, ˙OH, and Fe(iv) mediated oxidation processes. The elimination of arsenic encompasses two fundamental mechanisms: firstly, the direct adsorption of As(iii) by highly adsorbent flocculants like γ-FeOOH and magnetite (Fe3O4); secondly, the oxidation of As(iii) into As(v), followed by its reaction with siderite or other compounds to generate a dual coordination complex or iron arsenate, thus expediting its eradication. The anodic electrocoagulation system employing siderite as a filler exhibits remarkable efficiency and cost-effectiveness, while ensuring exceptional stability, thereby providing robust theoretical underpinnings for the application of electrocoagulation technology in arsenic removal.

Treatment of tomato paste wastewater by electrochemical and membrane processes: process optimization and cost calculation

This study investigated the treatment of wastewater from tomato paste (TP) production using electrocoagulation (EC) and electrooxidation (EO). The effectiveness of water recovery from the pretreated water was then investigated using the membrane process. For this purpose, the effects of independent control variables, including electrode type (aluminum, iron, graphite, and stainless steel), current density (25-75 A/m2), and electrolysis time (15-120 min) on chemical oxygen demand (COD) and color removal were investigated. The results showed that 81.0% of COD and 100% of the color removal were achieved by EC at a current density of 75 A/m2, a pH of 6.84 and a reaction time of 120 min aluminum electrodes. In comparison, EO with graphite electrodes achieved 55.6% of COD and 100% of the color removal under similar conditions. The operating cost was calculated to be in the range of $0.56-30.62/m3. Overall, the results indicate that EO with graphite electrodes is a promising pretreatment process for the removal of various organics. In the membrane process, NP030, NP010, and NF90 membranes were used at a volume of 250 mL and 5 bar. A significant COD removal rate of 94% was achieved with the membrane. The combination of EC and the membrane process demonstrated the feasibility of water recovery from TP wastewater.

Advancements in combined electrocoagulation processes for sustainable wastewater treatment: A comprehensive review of mechanisms, performance, and emerging applications

This review explores the potential and challenges of combining electrochemical, especially electrocoagulation (EC) process, with various - wastewater treatment methods such as membranes, chemical treatments, biological methods, and oxidation processes to enhance pollutant removal and reduce costs. It emphasizes the advantages of using electrochemical processes as a pretreatment step, including increased volume and improved quality of permeate water, mitigation of membrane fouling, and lower environmental impact. Pilot-scale studies are discussed to validate the effectiveness of combined EC processes, particularly for industrial wastewater. Factors such as electrode materials, coating materials, and the integration of a third process are discussed as potential avenues for improving the environmental sustainability and cost-effectiveness of the combined EC processes. This review also discusses factors for improvement and explores the EC process combined with Advanced Oxidation Processes (AOP). The conclusion highlights the need for combined EC processes, which include reducing electrode consumption, evaluating energy efficiency, and conducting pilot-scale investigations under continuous flow conditions. Furthermore, it emphasizes future research on electrode materials and technology commercialization. Overall, this review underscores the importance of combined EC processes in meeting the demand for clean water resources and emphasizes the need for further optimization and implementation in industrial applications.

Bioremediation efficiency of free and immobilized form of Aspergillus niger and Aspergillus tubigenesis biomass on tannery effluent

Untreated tannery effluent discharge, which causes severe environmental pollution. This research was performed to assess the bioremediation (multi-pollutant adsorption) potential of pre-identified and multi metal tolerant Aspergillus niger and Aspergillus tubigenesis through a stirred tank bioreactor in free and immobilized form. Physicochemical property analysis results showed that most of the tannery effluent properties were beyond the permissible limits. These A. niger and A. tubigenesis effectively immobilized on corncob and coir solid support material. The stirred tank bioreactor based bioremediation study revealed that the fungal biomass (Aspergillus niger and Aspergillus tubigenesis) immobilized coir and corncob material demonstrated remarkable multi-pollutant (TSS: 22.5% & 13.5%, TS: 29% & 22%, BOD: 21% & 10%, TDS: 28% & 19%, COD: 30% & 22%, Cr: 27% & 19%, Cu: 28% & 12%, and Pb: 48% & 29% respectively) adsorption potential in a week of treatment. Moreover, it reduced the toxicity of tannery effluent and promotes the sprouting of Oriza sativa seeds, as demonstrated by petri plate bioassay. These finding suggest that the metal-tolerant fungal isolates A. niger and A. tubigenesis demonstrated impressive bioremediation proficiencies in an immobilized state. A field investigation is required to assess the feasibility of this strategy on tannery effluent.

Membranes in Water Reclamation: Treatment, Reuse and Concentrate Management

In this article, an extensive examination is provided on the possible uses of membranes and hybrid processes in wastewater treatment. While membrane technologies face certain constraints, such as membrane fouling and scaling, the incomplete elimination of emerging contaminants, elevated expenses, energy usage, and brine disposal, there are approaches that can address these challenges. Methods such as pretreating the feed water, utilizing hybrid membrane systems and hybrid dual-membrane systems, and employing other innovative membrane-based treatment techniques can enhance the efficacy of membrane processes and advance sustainability.

Evaluation of Different Reverse Osmosis Membranes for Textile Dyeing and Finishing Wastewater Reuse

Different commercial reverse osmosis (RO) membranes from Vontron and DuPont Filmtec were evaluated for textile dyeing and finishing wastewater (TDFW) reuse in China. All six tested RO membranes produced qualified permeate meeting TDFW reuse standards at a water recovery ratio (WRR) of 70% in single batch tests. The rapid decline of apparent specific flux at WRR over 50% was mainly ascribed to feed osmotic pressure increase caused by concentrating effects. Multiple batch tests using Vontron HOR and DuPont Filmtec BW RO membranes with comparable permeability and selectivity demonstrated the reproducibility and showed low fouling development. The occurrence of carbonate scaling on both RO membranes was identified by scanning electron microscopy and energy disperse spectroscopy. No obvious organic fouling was detected on both RO membranes by attenuated total reflectance Fourier transform infrared spectrometry. From the orthogonal tests, with an integrated RO membrane performance index (i.e., 25% rejection ratio of total organic carbon + 25% rejection ratio of conductivity + 50% flux ratio of final to initial) as a target, the optimal parameters were determined as WRR of 60%, cross-flow velocity (CFV) of 1.0 m/s, temperature (T) of 20 °C for both RO membranes, while trans-membrane pressures (TMP) of 2 and 4 MPa were optimal for Vontron HOR RO membrane and DuPont Filmtec BW RO membrane, respectively. Both RO membranes with the optimal parameters produced good permeate quality for TDFW reuse and kept a high flux ratio of final to initial, demonstrating the effectiveness of the orthogonal tests.

Membrane Water Treatment for Drinking Water Production from an Industrial Effluent Used in the Manufacturing of Food Additives

An integrated membrane process for treatment of effluents from food additive manufacturing was designed and evaluated on a laboratory scale. The principal focus was water recovery with the possibility of its reuse as potable water. The industrial effluent presented high content of dyes and salts. It was red in color and presented brine characteristics. The whole effluent was fed into the integrated process in continuous flow. The steps of the process are as follows: sedimentation (S), adsorption by activated carbon (AC), ion exchange using resins (IEXR), and reverse osmosis (RO) (S–AC–IEXR–RO). The effect of previous operations was evaluated by stress-rupture curves in packaged columns of AC and IEXR, membrane flux, and fouling dominance in RO. Fouling was evaluated by way of the Silt Density Index and membrane resistance examination during effluent treatment. The integrated membrane process provided reclaimed water with sufficiently high standards of quality for reuse as potable water. AC showed a high efficiency for color elimination, reaching its rupture point at 20 h and after 5L of effluent treatment. IEXR showed capacity for salt removal, providing 2.2–2.5 L of effluent treatment, reaching its rupture point at 11–15 h. As a result of these previous operations and operating conditions, the fouling of the RO membrane was alleviated, displaying high flux of water: 20–18 L/h/m² and maintaining reversible fouling dominance at a feed flow rate of 0.5–0.7 L/h. The characteristics of the reclaimed water showed drinking water standards

The noteworthy chloride ions in reclaimed water: Harmful effects, concentration levels and control strategies

Chloride ions (Cl^-), which are omnipresent in reclaimed water, can cause various problems in water reuse systems, especially during water transmission and at end use sites. Although reverse osmosis (RO) is considered as an effective technology to reduce chloride, its high investment and complex maintenance requirements hinder its application in many water reclamation plants (WRPs). Recently, several technologies bringing new options to better deal with chloride have gained increased attention. This review provides detailed information on the harmful effects, concentration levels, and sources of chloride in reclaimed water and summarizes and discusses various chloride removal technologies, including non-selective methods (e.g., membrane filtration, adsorption and ion exchange, oxidation, and electrochemical methods) and selective methods (e.g. precipitation and specially designed electrochemical methods). Among these, Friedel's salt precipitation and capacitive deionization showed attractive development potential. This review also proposes a holistic framework for chloride control from aspects of "Fit-for-Purpose" planning, technical system development, and whole process optimization, which could facilitate the planning and operation of long-term sustainable water reuse practices.

Performance evaluation of whey flux in dead-end and cross-flow modes via convolutional neural networks

Effluent originating from cheese production puts pressure onto environment due to its high organic load. Therefore, the main objective of this work was to compare the influence of different process variables (transmembrane pressure (TMP), Reynolds number and feed pH) on whey protein recovery from synthetic and industrial cheese whey using polyethersulfone (PES 30 kDa) membrane in dead-end and cross-flow modes. Analysis on the fouling mechanistic model indicates that cake layer formation is dominant as compared to other pore blocking phenomena evaluated. Among the input variables, pH of whey protein solution has the biggest influence towards membrane flux and protein rejection performances. At pH 4, electrostatic attraction experienced by whey protein molecules prompted a decline in flux. Cross-flow filtration system exhibited a whey rejection value of 0.97 with an average flux of 69.40 L/m²h and at an experimental condition of 250 kPa and 8 for TMP and pH, respectively. The dynamic behavior of whey effluent flux was modeled using machine learning (ML) tool convolutional neural networks (CNN) and recursive one-step prediction scheme was utilized. Linear and non-linear correlation indicated that CNN model (R² - 0.99) correlated well with the dynamic flux experimental data. PES 30 kDa membrane displayed a total protein rejection coefficient of 0.96 with 55% of water recovery for the industrial cheese whey effluent. Overall, these filtration studies revealed that this dynamic whey flux data studies using the CNN modeling also has a wider scope as it can be applied in sensor tuning to monitor flux online by means of enhancing whey recovery efficiency.