Purification Of Effluents Research Articles

Bio-inspired chemistry for developing micro/nano structured nanofiber membranes for membrane distillation

Membrane distillation (MD) holds significant promise for effluent purification to mitigate the global water shortage. However, the existing petroleum-based MD membranes suffer from high costs, limited sustainability, and wetting issues. Herein, we employed biosynthetic bacterial cellulose (BC) as the substrate and successfully achieved a uniform and stable dispersion of ZnO nanoflowers onto the BC nanofibers through in-situ synthesis technology. After undergoing a fluorination process, a superhydrophobic membrane was prepared by the synergistic effect of micro/nano structures and low surface energy. The resulting membrane exhibited exceptional properties, including a remarkable contact angle of 151.7°, a substantial liquid entry pressure of 2.5 bar, and exhibiting structural integrity and high hydrophobicity even under harsh conditions. Furthermore, this strategy ensured exceptional membrane porosity (∼94.9 %), increased the permeation flux and reduced conductive heat transfer, thereby enhancing the thermal efficiency of the membrane. Furthermore, the membrane demonstrated effective bactericidal activity and self-cleaning capability, facilitating easy cleaning and extending service life. These properties endow the membrane with an impressive durability. After 96 h of continuous operation, the membrane maintained a stable permeation flux of 10.29 L m−2 h−1 and an extraordinary salt rejection rate exceeding 99.9 %. Notably, even with the addition of sodium dodecyl sulfate to the feed, the membrane exhibited stable permeation flux and outstanding antiwetting properties. In summary, the MD membrane fabricated using the bio-inspired chemistry demonstrated a promising potential for long-term applications in direct contact MD operations.

Combined activated sludge and sand filtration for purification of UASB effluent with high suspended solids from water hyacinth juice

Rapid biogasification of water hyacinth, a globally overgrown species, using compression and up-flow anaerobic sludge blanket (UASB) treatment of the juice has recently been proposed. This study aimed to establish a post-purification system for UASB-treated juice to effectively utilize the remaining nutrients for valuable products, such as vegetables and microalgae. To easily remove hard-to-degrade suspended solids (SS) and organic matter from UASB-treated juice, the activated sludge (AS) and sand filtration processes—conventional biological treatments—were introduced, with a focus on their physical treatment properties.Over 76% of SS and 43% of the organic carbon were removed from UASB-treated juice during the process. The hydraulic retention time of the AS was reduced to one day, indicating the potential of minimizing the facility size. The light transmittance, which is crucial for microalgae mediums, improved sevenfold. Even after most of the SS was removed by the AS, the sand filtration further increased the light transmittance by 1.4 times. The AS effectively removed most of the SS and organic matter, whereas sand filtration enhanced the treatment stability and further improved the light transmittance. NH4+ was mostly oxidized to NO3-, which is less toxic to plants. The total inorganic nitrogen content remained high after treatment, suggesting that UASB effluents from water hyacinth can be used as a nutrient source for hydroponics and microalgae cultivation in developing countries.

A photocatalysis-self-Fenton system based on NCDs@ZnIn2S4 composites at neutral pH and low amount of Fe2+ for the effective degradation of antibiotics

Photocatalysis-self-Fenton combining photocatalytic production of H2O2 with Fenton reaction has been a hotspot, but the pH limitation and iron sludge production problems remain unsolved. Herein, we proposed a self-fenton system based on N-doped carbon dots modified ZnIn2S4 (NCDs@ZnIn2S4) composites that exhibits effective degradation of antibiotics under neutral pH using low amounts of Fe2+. The decoration of ZnIn2S4 with NCDs significantly increased the surface area, visible light absorption, charge transfer ability and oxygen adsorption ability. NCDs@ZnIn2S4 composites exhibited a high H2O2 production rate (1528 μM g−1•h−1) under visible light, which was 1.9 and 5.3 times higher than ZnIn2S4 and NCDs, respectively. Meanwhile, the Fe2+/NCDs@ZnIn2S4 system with a low concentration of Fe2+(1 mg/L) could remove over 95% levofloxacin and oxytetracycline within 30 min. Interestingly, the highest degradation efficiency occurred under neutral pH. Quenching experiments and analytical measurements indicated that the high catalytic performance under pH = 7 with low amounts of Fe2+ stemmed from the higher amount of inner-generate H2O2 under neutral pH and easy regeneration of Fe2+ by photoinduced electrons for high •OH yields. Additionally, the Fe2+/NCDs@ZnIn2S4 system exhibited high degradation performance under different water matrix and ultrahigh degradation efficiency towards levofloxacin under real sunlight irradiation. The work shows the prospects of photocatalysis-self-Fenton systems for overcoming the pH limitation and the difficulty of iron sludge separation in the purification of effluents.

Occurrence of Uncultured Legionella spp. in Treated Wastewater Effluent and Its Impact on Human Health (SCA.Re.S Project).

Wastewater treatment plants (WWTPs) provide optimal conditions for the environmental spread of Legionella. As part of the Evaluation of Sanitary Risk Related to the Discharge of Wastewater to the Ground (SCA.Re.S) project, this study was conducted to evaluate the presence of Legionella in WWTP effluent and in groundwater samples collected from two wells located downstream from the plant. The samples were analyzed to determine the concentrations of Legionella spp using the standard culture-based method and molecular techniques, followed by genomic sequencing analysis. Legionella was detected only with the molecular methods (except in one sample of effluent positive for L. pneumophila serogroup 6), which showed viable Legionella pneumophila and L. non-pneumophila through the use of free DNA removal solution in both the effluent and groundwater, with concentrations that progressively decreased downstream from the plant. Viable L. pneumophila appeared to be slightly more concentrated in warm months. However, no significant differences (p ≥ 0.05) in concentrations between cold and warm months were observed. A genotypic analysis characterized the species present in the samples and found that uncultured Legionella spp, as yet undefined, constituted the prevalent species in all the samples (range 77.15-83.17%). WWTPs play an important role in the hygienic and sanitary quality of groundwater for different uses. The application of Legionella control systems during the purification of effluents is warranted to prevent possible outbreaks of legionellosis.

Realization of oil/bacteria-containing effluent purification and self-power for water monitoring based on solar-driven interfacial evaporation

Low-energy separation techniques are urgently needed to obtain clean water from complex effluent sources, especially in light of the increasing global water and energy shortages. Herein, we proposed a de novo integrated strategy that simultaneously achieved the purification of oil/bacteria-containing complex wastewater/seawater while generating self-power for monitoring the quality of purified water via solar-driven water evaporation (SDWE) of effluent utilizing a modified MXene-based aerogel (M@PCM-4). This aerogel featured a vertically aligned porous cellular microchannel structure, and it possessed photothermal conversion and self-power functions. Our study demonstrates high oil–water separation efficiency (>99.75 %), bacterial retention rate (∼100 %), and power generation (0.22 V), which holds practical significance. The designed strategy offered a potential route for addressing the dual challenges of clean water scarcity and sustainable energy production.

Evaluation of the potential ultrafiltration to improve the quality of secondary effluents in tertiary treatment and reuse

Unsatisfactory effluent purification, limited to secondary treatment, considerably restricts the reuse of treated water. In this study, the performance of three ceramic ultrafiltration (UF) membranes UF1 (0.02 μm), UF2 (0.05 μm), and UF3 (0.1 μm) was evaluated for the recovery of secondary effluent (SE) from a wastewater treatment plant (WWTP) in Kenitra. The effects of different parameters on treated water quality were assessed, including transmembrane pressure (TMP), circulation velocity (CV), and membrane pore size. The results indicated that the UF1 membrane was more effective than UF2 and UF3, achieving maximum removal rates for chemical oxygen demand (COD), biochemical oxygen demand at 5 days (DBO5), and total suspended solids (TSS) of 75%, 72%, and 96%, respectively, under optimal operating conditions of TMP at 1 bar and CV at 1 m/s. UF2 achieved removal rates of 70%, 71%, and 94% for COD, BOD5, and TSS, respectively, under the same conditions. For UF3, the highest removal rates were 64%, 62%, and 92% for COD, BOD5, and TSS, respectively, at 2 bar and 1 m/s. Moreover, the experiments also demonstrated that an increase in TMP results in increased permeate flux and fouling resistance, while CV has also an impact on the permeate flux. Additionally, a very satisfactory retention rate for microorganisms was observed, exceeding 90%, with no presence of helminth eggs (100% removal) detected in the treated water. Nutrient elimination was also notable, with reductions of 14% for total Kjeldahl nitrogen (TKN) and 50% for total phosphorus (TP) using the UF1 membrane, which was selected based on its optimal performance.

Co-removal of mercury and organic dye via the rectangle-shaped nanosheets loaded hydrochar: Surface interactions and DFT calculations

Inorganic and organic pollutants usually co-exist in practical wastewater, leading to difficult co-removal processes due to their different physiochemical properties. In this study, the palygorskite nanosheets loaded hydrochar (PNLH) was synthesized for the mercury (Hg) and methylene blue (MB) co-contaminated wastewater. The physicochemical characteristics of PNLH were investigated comprehensively, and the maximum capacity of Hg(II) and MB reached 149 and 153 mg/g, respectively. Based on analysis, the surface interactions between PNLH with Hg(II) and MB included complexation, hydrogen bonding, pore filling, etc. More importantly, the performance of PNLH was improved in the Hg(II)-MB binary system, while the synergistic effects were attributed to the bridging interactions and formation of complexations between Hg(II) and MB. The density functional theory (DFT) method was applied to demonstrate that the oxygen-containing functional groups such as O–Mg, O–Al, and –OH introduced by the clay greatly enhanced the interactions, and the synergistic adsorption mechanism was also elucidated. The regeneration experiments, column studies, and economic feasibility analysis further demonstrated the practicality of PNLH for effluent purification. This study provides a solution for environmental remediation materials dealing with inorganic–organic co-polluted wastewater.

Textile effluent treatments using natural adsorbents and vapor absorption technology: A box behnken design approach

The untreated effluents from textile industries pose significant hazards to the environment and human health, exacerbating challenges in effluent disposal management and water scarcity. In response, various methods, particularly adsorption, have been widely employed in chemical and process industries to remove contaminants. This study focuses on converting industrial effluents into potable water using natural adsorption and vapor absorption techniques and optimizing the method with Response Surface Methodology (RSM) analysis using Box-Behnken design (BBD). The optimized condition obtained through RSM was replicated and found to have an adsorption capacity of 45 % after the column and 65 % total removal after the vapor absorption column. Activated carbon samples from textile industries underwent characterization techniques such as FTIR, XRD, TGA, and SEM analyses. Different adsorbing materials including date seeds, tamarind seeds, and palm leaves were utilized for effluent purification. Chemical analyses were conducted on raw effluent, settled effluent, and condensed water and showed that there is a certain metal ion removal. Through this approach, the study aims to provide an eco-friendly and economically viable solution for effluent treatment, addressing both environmental concerns and resource management challenges and a possible coupling of two different approaches into a viable solution.

Physicochemical and photocatalytic properties of biogenic ZnO and its chitosan nanocomposites for UV-protection and antibacterial activity on coated textiles

The textiles for medical use and the purification of textile factory effluents have become the most crucial part of the human healthcare sector. In this study bioactive compounds produced by four distinct plant extracts were used for the synthesis of zinc oxide nanoparticles. The four different ZnO nanoparticles were comprehensively characterized by different analytical techniques. XRD analysis revealed the crystalline nature and phase purity of the ZnO nanoparticles. FTIR spectra provided information on the function of plant extracts in the stabilization or capping process. The size distribution and morphological diversity of the nanoparticles were further clarified by SEM and TEM images. The photocatalytic degradation activity of the four ZnO nanoparticles on two different dyes showed that ZnO nanoparticles prepared from A. indica were most effective for the degradation of 98 % and 91 % of Rhodamine B and Alizarin red dye respectively. The selected ZnO nanoparticles from A. indica were used to prepare ZnO-chitosan nanocomposites before coating on cotton fabrics. The hydrophobicity, UV protection factor, and antibacterial activity of ZnO-chitosan nanocomposites, when coated on cotton fabrics, were also examined. The overall results demonstrated the ZnO and ZnO-chitosan nanocomposite prepared in the present study as a promising material for environmental remediation application.

Electrocatalytic denitrification biofilter for advanced purification of chlorophenols via ceramsite-based Ti/SnO2–Sb particle electrode: Performance, microbial community structure and mechanism

In response to the demand for advanced purification of industrial secondary effluent, a new method has been developed for treating chlorophenol wastewater using the novel ceramsite-based Ti/SnO2–Sb particle electrodes (Ti/SnO2–Sb/CB) enhanced electrocatalytic denitrification biofilter (EDNBF-P) to achieve removal of chlorophenols (CPs), denitrification, and reduction of effluent toxicity. The results showed that significantly improved CPs and TN removal efficiency at low COD/N compared to conventional denitrification biofilter, with CPs removal rates increasing by 0.33%–59.27% and TN removal rates increasing by 12.53%–38.92%. Under the conditions of HRT = 2h, 3V voltage, charging times = 12h, and 25 °C, the concentrations of the CPs in the effluent of EDNBF-P were all below 1 mg/L, the TN concentration was below 15 mg/L, while the effluent toxicity reached the low toxicity level. Additionally, the Ti/SnO2–Sb/CB particle electrodes effectively alleviated the accumulation of NO2−-N caused by applied voltage. The Silanimonas, Pseudomonas and Rhodobacter was identified as the core microorganism for denitrification and toxicity reduction. This study validated that EDNBF-P could achieve synergistic treatment of CPs and TN through electrocatalysis and microbial degradation, providing a methodological support for achieving advanced purification of chlorophenol wastewater with low COD/N in industrial applications.

Effective Biosorption of Cesium and Strontium Ions from Aqueous Solutions Using Silica Loaded with Aspergillus brasiliensis

In this study, the batch technique was used for the sorption of Sr(II) and Cs(I) onto silica loaded with Aspergillus brasiliensis (AB@S). The precipitation technique was used to synthesize the AB@S bio-sorbent, which was then evaluated using several analytical instruments such as XRD, FT-IR, and SEM. The results of this investigation revealed that the sorption process had a short equilibrium time (40 min). The distribution coefficient values have a sequence order Sr(II) ˃ Cs(I). AB@S sorbent has saturation capacity for Sr(II) and Cs(I) 72.2 and 26.1 mg g−1, respectively. The reaction kinetics follow the pseudo-second-order model with capacity values of 5.01 and 3.53 mg g−1 for Sr(II) and Cs(I), respectively. Applicability of Langmuir isotherms has capacity values of 66.3 and 23.38 mg g−1 for Sr(II) and Cs(I), respectively. Thermodynamics data are endothermic and spontaneous. The AB@S is a promising bio-sorbent for the removal of 85Sr and 134Cs from simulated radioactive waste (SRW). The investigation proved that the AB@S is suitable to adsorb Sr(II) and Cs(I) from aqueous solutions and could be considered potential material for the purification of effluent contaminated with these ions.

Facile preparation of Fe2O3 catalyst and assessment of its photodegradation performance for industrial effluent purification

This study focuses on synthesizing nano-scaled Fe2O3 particles using Araucaria columnaris (Cook's pine) leaf extract under atmosphere circumstances. These extracts serve as both a reductant and a stabilizer. Fe2O3 nanoparticle synthesis was confirmed through a comprehensive characterization process using many analytical techniques. The analysis of XRD patterns indicated that the examined samples consisted of nanoparticles of γ-Fe2O3, exhibiting a cubic crystal structure with a high degree of crystallization. Furthermore, the calculated crystallite size was resolute to be 24.5 nm. The scanning electron microscopy pictures revealed that the created samplesexhibited a combination of spherical and polyhedral morphologies. The investigation of optical characteristics, such as light absorption and bandgap width, was conducted usingUV–visible spectroscopy, employing a bandgap energy value of 3.78 eV. The study aimed to assess the removal effectiveness of Eosin yellow, Malachite green, Reactive black, and Rhodamine 6G dyes using Fe2O3 nanoparticles synthesized as a photocatalyst which exhibited remarkable photocatalytic efficacy in the breakdown of dyes when exposed to sunlight, and the reaction period of 90 min resulted in a maximum degradation rate of 97.4 %. Considering the promising results, utilizing Fe2O3 nanoparticles as a photocatalyst for degrading dyes in wastewater is feasible. Additionally, Araucaria columnaris leaf extract can be an environmentally friendly and economically viable method for synthesizing Fe2O3 nanoparticles.

Computer simulation of a solar multi-effect distillation multi-stage flash effluent purification system

Abstract This study integrates multi-effect distillation (MED), multi-stage flash (MSF) evaporation, and solar interface evaporation technologies to enhance water purification processes. We evaluate the material and performance of interface evaporators, with a particular focus on managing the energy balance in solar water evaporation. The research further develops thermal regulation in photothermal materials to maximize light absorption, minimize heat loss, and speed up steam conversion. We employ a novel approach using corn starch and ionic liquid-modified silica hydrogels, noted for their hydrophilicity and broad-spectrum light absorption. The goal is to assess these hydrogels for photothermal conversion efficiency and salt resistance, examining their evaporation performance across various media—pure water, highly saline water, and oily wastewater—and their effectiveness in purifying industrial sewage. Monomer [VEIm]Br and cross-linking agent polymerization occurred to prepare the obtained SiO 2 – PILs.Ag / PPy / SiO 2 – PILs surface of polypyrrole and Ag particles presenting a three-dimensional porous structure is able to enhance the light absorption performance, between 200-2500 nm range of light absorption rate as high as 90%. Experiments proved the introduction of ionic liquid grafted silica on the introduction of the mechanism to improve the thermal insulation and salt resistance for the actual wastewater purification to provide a strategy.

Metal Recovery from Wastewater Using Electrodialysis Separation

Electrodialysis is classified as a membrane separation process in which ions are transferred through selective ion-exchange membranes from one solution to another using an electric field as the driving force. Electrodialysis is a mature technology in the field of brackish water desalination, but in recent decades the development of new membranes has made it possible to extend their application in the food, drug, and chemical process industries, including wastewater treatment. This work describes the state of the art in the use of electrodialysis (ED) for metal removal from water and wastewater. The fundamentals of the technique are introduced based on the working principle, operational features, and transport mechanisms of the membranes. An overview of the key factors (i.e., the membrane properties, the cell configuration, and the operational conditions) in the ED performance is presented. This review highlights the importance of studying the inter-relation of parameters affecting the transport mechanism to design and optimize metal recovery through ED. The conventional applications of ED for the desalination of brackish water and demineralization of industrial process water and wastewater are discussed to better understand the key role of this technology in the separation, concentration, and purification of aqueous effluents. The recovery and concentration of metals from industrial effluents are evaluated based on a review of the literature dealing with effluents from different sources. The most relevant results of these experimental studies highlight the key role of ED in the challenge of selective recovery of metals from aqueous effluents. This review addresses the potential application of ED not only for polluted water treatment but also as a promising tool for the recovery of critical metals to avoid natural resource depletion, promoting a circular economy.

Membrane process and adsorption on pine nut shell for removal of dye from synthetic wastewater

ABSTRACT Purification methods such as membrane technology and adsorption have been studied for the purification of textile effluents. This article aimed to evaluate the membrane separation process and adsorption on pine nut shell, separately and sequentially, for reactive dye blue 5G removal from a synthetic effluent. The membrane separation process was carried out in a front filtration module using polymeric membranes. The maximum dye retention was 35.9% using a regenerated cellulose membrane, with agitation and a pressure of 0.5 bar. The permeate flux was fully restored after cleaning the membrane. In the adsorption using pine nut shell, the best results were at pH 2, 50°C, and 50 ppm, with 85% dye removal. The Freundlich isotherm showed the best fit to the data, as did the pseudo-second-order kinetic model. The thermodynamic parameters indicated that the adsorption is of the physical type, with the process being endothermic and spontaneous. In the combined process, the permeate from the membrane separation process was subjected to adsorption on pine nut shell, achieving a removal rate of 98.7 for the initial concentration of 50 ppm. Therefore, this work shows the potential of pine nut shell as an adsorbent, not only to purify textile effluents but also to add value to a waste product, indicating that the combination of membrane technology and adsorption on pine nut shell could be an alternative for the treatment of textile effluents containing the reactive dye 5G blue.

The shells of edible freshwater snails as a biosorbent for multi-metal ions from wastewater: Implication in effluent purification and waste valorisation

The generation of waste shells of edible freshwater snails, Filopaludina bengalensis and Pila globosa, following human consumption and use in aquaculture, encourages their utilisation as a potential biomaterial. In this experiment, we employed the shell dust derived from F. bengalensis (FSD) and P. globosa (PSD) shells as a biosorbent of Cd2+, Co2+, Cr2O72- and Cu2+ from single- and multi-metal solutions. The results of batch adsorption experiments and characterisation of FSD and PSD using SEM, EDS, ICP-OES, FTIR, and XRD indicated that the metal ion removal process involved chemical adsorption (formation of CdCO3, Cu2CO3(OH)2 and CoCO3), ion exchange (reduced quantity of various elements on the shell dust following their release into the solution during adsorption) and surface precipitation. The best-fitted Langmuir isotherm specified monolayer adsorption with maximum adsorption capacity for Cd2+ (in single-metal system: FSD- 254.42, PSD- 327.76 mg/g; in multi-metal system: FSD: 93.79, PSD: 94.45 mg/g) and Cu2+ (in single-metal system: FSD- 234.63, PSD- 289.71 mg/g; in multi-metal system: FSD: 150.01, PSD: 160.51 mg/g). In multi-metal systems, the adsorption of Cd2+ and Cu2+ was antagonistic, and the adsorption of Co2+ and Cr2O72- was synergistic in nature. The thermodynamic parameters suggest that the adsorption is endothermic, feasible and spontaneous. The successful removal of metal ions from single- and multi-metal solutions and real wastewater recommended FSD and PSD as eco-friendly and low-cost biosorbent for wastewater amelioration with implication in waste valorisation.

A collaborative effect of solid-phase denitrification and algae on secondary effluent purification

This study explored the collaborative effect on nutrients removal performance and microbial community in solid-phase denitrification based bacteria-algae symbiosis system. Three biodegradable carriers (apple wood, poplar wood and corncob) and two algae species (Chlorella vulgaris and Chlorella pyrenoidosa) were selected in these bacteria-algae symbiosis systems. Results demonstrated that corncob as the carrier exhibited the highest average removal efficiencies of total nitrogen (83.7%–85.1%) and phosphorus removal (38.1%–49.1%) in comparison with apple wood (65.8%–71.5%, 25.5%–32.7%) and poplar wood (42.5%–49.1%, 14.2%–20.7%), which was mainly attributed to the highest organics availability of corncob. The addition of Chlorella acquired approximately 3%–5% of promotion rates for nitrated removal among three biodegradable carriers, but only corncob reactor acquired significant promotions by 3%–11% for phosphorous removal. Metagenomics sequencing analysis further indicated that Proteobacteria was the largest phylum in all wood reactors (77.1%–93.3%) and corncob reactor without Chlorella (85.8%), while Chlorobi became the most dominant phylum instead of Proteobacteria (20.5%–41.3%) in the corncob with addition of Chlorella vulgaris (54.5%) and Chlorella pyrenoidosa (76.3%). Thus, the higher organics availability stimulated the growth of algae, and promoted the performance of bacteria-algae symbiosis system based biodegradable carriers.

Algae-Bacteria cooperated microbial ecosystem: A self-circulating semiartificial photosynthetic purifying strategy

The microbial fuel cell (MFC) is a promising bio-electrochemical technology that enables simultaneous electricity generation and effluent purification. Harnessing solar energy to provide sustainable power for MFC operation holds great potential. In this study, a semiartificial photosynthetic self-circulating MFC ecosystem is successfully established through the collaboration of electrogenic microorganisms and photosynthetic algae. The ecosystem can operate continuously without carbon sources and produces a voltage of 150 mV under irradiation. The irradiation doubles the maximum power density of the ecosystem, reaching 8.07 W/m2 compared to dark conditions. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) suggest a higher diffusion capacity or faster electron replenishment ability within the ecosystem. Furthermore, the capacity of ecosystem for removing chromium (Cr(VI)) has been investigated comprehensively. Under irradiation, the ecosystem demonstrates a 2.25-fold increase in Cr(VI) removal rate compared to dark conditions. Finally, the results of 16S rRNA amplicon sequencing indicates an increase in the relative abundance of strict and facultative aerobic electroactive bacteria in the ecosystem, including Citrobacter (21 %), Bacillus (15 %) and Enterococcus (6 %). The ecosystem offers a novel, self-sustaining approach to address the challenges of energy recovery and environmental pollution.

Novel insight into secondary effluent quality improvement and ultrafiltration fouling mitigation by UV/peracetic acid pretreatment

Ultrafiltration (UF) technology is widely used in the treatment for deep purification of municipal secondary effluent, however, the membrane fouling and low removal of N, P, and organic matter during actual operation have been the main bottlenecks limiting its wide-spread application. To address the above problems, this study employed peracetic acid (PAA) and UV/PAA to evaluate the effects of PAA-based pre-oxidation on ultrafiltration membrane fouling and secondary effluent water quality. The results demonstrated that the activated PAA pre-oxidation could prominently enhance the hydrophilicity of effluent organic matter, effectively destroy the high molecular weight organic matter and mineralize the low molecular weight organic matter. PAA and its metabolites, as well as the by-products of EfOM, increased the C/P ratio in water samples from 118 to 563 and the C/N ratio from 0.86 to 8.53. After UV/20 mg/L PAA pretreatment, the reversible and irreversible membrane fouling resistance significantly decreased by 55.97 % and 65.67 %, respectively. Moreover, the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory showed lower adhere potential of the foulants to the membrane surface. In general, UV/PAA as ultrafiltration pretreatment has a huge potential for secondary effluent treatment for membrane fouling mitigation and water quality improvement.

Purification of Industrial Effluent by Gas Hydrate-based (HyPurif) Process

This study presents a sustainable HyPurif process for managing and recycling industrial water effluent, utilizing gas hydrate-based technology to purify complex effluent. This work purifies two effluents: one from a wastewater treatment plant (WWTP) and the other from a spent caustic treatment plant (SCTP). Various hydrate formers, including propane, HFC134a, and cyclopentane (6 mol %), were selected, as they typically form hydrates closer to ambient conditions. Hydrate formation experiments with effluent water were performed at 278.30 K using pure propane and HFC134a gas. Based on the kinetics of hydrate growth, the study was extended to a mixture (50:50%) of propane and HFC134a, operating at a pressure of 0.6 MPa. The mixture of propane and HFC134a has shown the desired result of forming the hydrate in the gas phase and having high separation efficiency. The results showed that the formation and dissociation of hydrates resulted in a separation efficiency of 80–95%. For instance, in the purified water, the biological oxygen demand (BOD) decreased from 2097 mg/L in the effluent sample to 220 mg/L in purified water (purification efficiency of 90.5%). The chemical oxygen demand (COD) decreased from 3100 mg/L in the effluent sample to 503 mg/L in purified water (purification efficiency of 84%). Total dissolved solids (TDS) were reduced from 89,632 mg/L in the effluent water to 14,698 mg/L in purified water (purification efficiency of 84%). Total suspended solids (TSS) were reduced from 35 mg/L in the effluent water to 3.5 mg/L in purified water (purification efficiency of 90%). However, the purification efficiency for free ammonia and residual chlorine was lower. The concentration of free ammonia decreased from 7 mg/L in the effluent sample to 1.89 mg/L in the purified water (purification efficiency of 73%), and residual chlorine reduced from 0.8 mg/L in the effluent sample to 0.2 mg/L in the purified water (purification efficiency of 75%). Water recovery of ≥40% was achievable per pass, which could be increased, but at the expense of purification efficiency. To the best of our knowledge, this is the first study on the purification of such complex wastewater containing organic and inorganic compounds, heavy metals, and various minerals using the HyPurif process.