Real Wastewater Treatment Research Articles

Electrocatalytic nitrate reduction on Fe, Fe3O4, and Fe@Fe3O4 cathodes: Elucidating structure-sensitive mechanisms of direct electron versus hydrogen atom transfer

Electrochemical nitrate reduction (NO3RR) offers a promising avenue for treating nitrate-contaminated water and recovering ammonia (NH3), yet the complexities of direct electron transfer (DET) and hydrogen atom transfer (HAT) mechanisms crucial for efficiency remain elusive. This study bridges the gap with a combined experimental and theoretical approach, elucidating the impact of catalyst structure on NO3RR pathways. We discover that catalysts favoring strong NO3− adsorption and efficient water dissociation were more inclined towards DET, enhancing denitrification. The Fe@Fe3O4/FF cathode, leveraging the synergistic interplay between metallic Fe and Fe3O4, excelled in NO3RR via DET, achieving an NH3 yield of 0.28 mmol h−1 cm−2 and a Faradaic efficiency of 95.7% for NH3 at -1.6 V (vs. SCE), with minimal nitrite accumulation at 100 mmol/L nitrate. Conversely, the Fe/FF and Fe3O4/CC cathodes showed reduced NH3 production and increased nitrite levels, attributed to the lack of Fe3O4 and metallic Fe, respectively, resulting in a dominant HAT mechanism. Moreover, Fe@Fe3O4/FF facilitated complete denitrification in real wastewater treatment by harnessing Cl− for electrochemically mediated breakpoint chlorination. This research not only deepens our understanding of NO3RR mechanisms but also paves the way for designing superior nitrate reduction catalysts.

Accurate prediction and intelligent control of COD and other parameters removal from pharmaceutical wastewater using electrocoagulation coupled with catalytic ozonation process.

In this study, we employed the response surface method (RSM) and the long short-term memory (LSTM) model to optimize operational parameters and predict chemical oxygen demand (COD) removal in the electrocoagulation-catalytic ozonation process (ECOP) for pharmaceutical wastewater treatment. Through RSM simulation, we quantified the effects of reaction time, ozone dose, current density, and catalyst packed rate on COD removal. Then, the optimal conditions for achieving a COD removal efficiency exceeding 50% were identified. After evaluating ECOP performance under optimized conditions, LSTM predicted COD removal (56.4%), close to real results (54.6%) with a 0.2% error. LSTM outperformed RSM in predictive capacity for COD removal. In response to the initial COD concentration and effluent discharge standards, intelligent adjustment of operating parameters becomes feasible, facilitating precise control of the ECOP performance based on this LSTM model. This intelligent control strategy holds promise for enhancing the efficiency of ECOP in real pharmaceutical wastewater treatment scenarios. PRACTITIONER POINTS: This study utilized the response surface method (RSM) and the long short-term memory (LSTM) model for pharmaceutical wastewater treatment optimization. LSTM predicted COD removal (56.4%) closely matched experimental results (54.6%), with a minimal error of 0.2%. LSTM demonstrated superior predictive capacity, enabling intelligent parameter adjustments for enhanced process control. Intelligent control strategy based on LSTM holds promise for improving electrocoagulation-catalytic ozonation process efficiency in pharmaceutical wastewater treatment.

Treatment of real carwash wastewater using high-efficiency and energy-saving electrocoagulation technique

This study focused on the treatment of actual wastewater from a car wash facility using electrocoagulation. The primary objective was to decrease chemical oxygen demand (COD) and eliminate turbidity by employing various electrodes such as Stainless Steel (SS) 304, Galvanized Iron (GI), and aluminum foil (α-Al) in a batch configuration. Several factors including contact time, current density, initial pH, and electrode material were examined to optimize process efficiency. The sludge generated during electrocoagulation was analyzed using Scanning Electron Microscopy/Energy-Dispersive X-ray Spectrometry (SEM-EDS). The results indicated that COD removal efficiency initially decreased between 30 and 60 min before improving. The data for COD, turbidity, and total phosphate reduction aligned well with the pseudo-first-order kinetic model, with R2 values of 0.275, 0.898, and 0.522, respectively. Minor variations were observed in pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), and alkalinity, while the temperature increased from 12 to 18.6 °C. Optimal removal efficiency for turbidity, total phosphate, and COD was achieved at pH = 6. The study demonstrated that higher current density resulted in enhanced COD reduction and turbidity removal. Chloride levels decreased with increasing applied current. The α-Al electrode exhibited superior performance compared to SS 304 and GI electrodes, with notable pH fluctuations during the process. UV–visible absorption spectra indicated differences in treated wastewater patterns based on the electrode utilized. SEM analysis revealed distinct characteristics of sludge produced by different electrodes. Energy and electrode consumption varied among the electrodes, with SS 304 displaying the lowest values.

Ultrasmall copper-metal organic framework (Cu-MOF) quantum dots decorated on waste derived biochar for enhanced removal of emerging contaminants: Synergistic effect and mechanistic insight

This study proposes a novel one-pot hydrothermal impregnation strategy for surface decoration of waste derived pisum sativum biochar with zero‒dimensional Cu‒MOF Quantum dots (PBC‒HK), with an average particle size of 5.67 nm, for synergistic removal of an emerging sulfur containing drug pantoprazole (PTZ) and Basic Blue 26 (VB) dye within 80 min and 50 min of visible-light exposure, respectively. The designed Integrated Photocatalytic Adsorbent (IPA) presented an enhanced PTZ removal efficiency of 95.23% with a catalyst loading of 0.24 g/L and initial PTZ conc. 30 mg/L at pH 7, within 80 min via synergistic adsorption and photodegradation under visible-light exposure. While, on the other hand, 96.31% VB removal efficiency was obtained in 50 min with a catalyst dosage of 0.20 g/L, initial VB conc. 60 mg/L at pH 7 under similar irradiation conditions. An in-depth analysis of the synergistic adsorption and photocatalysis mechanism resulting in the shortened time for the removal of contaminants in the synergistic integrated model has been performed by outlining the various advantageous attributes of this strategy. The first-order degradation rate constant for PTZ was found to be 0.04846 min−1 and 0.04370 min−1 for PTZ and VB, respectively. Adsorption of contaminant molecules on the biochar (PS‒BC) surface can facilitate photodegradation by accelerating the kinetics, and photodegradation promotes regeneration of adsorption sites, contributing to an overall reduction in operation time for removal of contaminants. Besides enhancing the adsorption of targeted pollutants, the carbon matrix of IPAs serves as a surface for adsorption of intermediates of degradation, thereby minimizing the risk of secondary pollution. The photogenerated holes present in the VB is responsible for the generation of •OH radicals. While, the photogenerated electrons present in the CB are captured by Cu2+ of the MOF metal center, reducing it to Cu+, which is subsequently oxidized to produce additional •OH species in the aqueous medium. This process leads to effective charge separation of the photogenerated charge carriers and minimizes the probability of charge recombination as evident from photoluminescence (PL) analysis. Meanwhile, PL studies, EPR and radical trapping experiments indicate the predominant role of •OH radicals in the removal mechanism of PTZ and VB. The investigation of the degradation reaction intermediates was confirmed by HR‒LCMS, on the basis of which the plausible degradation pathway was elucidated in detail. Moreover, effects of pH, inorganic salts, other organic compounds and humic acid concentration have been investigated in detail. The environmental impact of the proposed method was comprehensively evaluated by ICP-OES analysis and TOC and COD removal studies. Furthermore, the economic feasibility and the cost-effectiveness of the catalyst was assessed to address the potential for large scale commercialization. Notably, this research not only demonstrates a rational design strategy for the utilization of solid waste into treasure via the fabrication of IPAs based on MOF Quantum dots (QDs) and waste-derived biochar, but also provides a practical solution for real wastewater treatment systems for broader industrial applications.

Electrocoagulation removal of COD and TDS from real municipal wastewater sourced from the Euphrates River using multipole arrangement

This study investigated the performance of the electrocoagulation (EC) process for removing organic pollutants, as measured by chemical oxygen demand (COD), and reducing total dissolved solids (TDS) from real municipal wastewater sourced from the Euphrates River. A systematic approach was followed, where initial control tests were conducted to identify the optimal electrode configuration, which was a multipole arrangement of aluminum electrodes.The independent operating parameters studied were electrolysis time (10–60 min), applied current (0.2–1.4 A), and mixing speed (50–250 rpm). The response surface methodology (RSM), facilitated by a Box-Behnken design (BBD), was employed to model and optimize the EC process. The developed mathematical models revealed that the COD removal efficiency, final TDS value, and energy consumption were strongly dependent on the coagulation process parameters.The results showed that under the optimized conditions of 60 min of electrolysis time, 1 A of applied current, and 50 rpm mixing speed, a maximum COD removal efficiency of 92.43 % was achieved. At these optimal values, the final TDS concentration was reduced to 1299 ppm. The energy consumption for the batch EC process was also determined, with the lowest value being 5.47 kWh/m3.The findings demonstrate the effectiveness of the electrocoagulation process, particularly when utilizing a multipole electrode arrangement, for the treatment of real municipal wastewater. The developed models and optimization approach can be used to predict the performance and determine the optimal operating conditions for similar wastewater treatment applications. Future research prospects include investigating the removal of other pollutants, integrating the EC process with other treatment technologies, and evaluating the long-term economic feasibility of the system.

Linear and nonlinear regression modelling of industrial dye adsorption using nanocellulose@chitosan nanocomposite beads

Nanocellulose@chitosan (nc@ch) composite beads were prepared via coagulation technique for the elimination of malachite green dye from aqueous solution. As malachite green dye is highly used in textile industries for dyeing purpose which after usage shows fatal effects to the ecosystems and human beings also. In this study the formulated nanocellulose@chitosan composite beads were characterized by Particle size analysis (PSA), Field emission scanning electron microscopy (FESEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis were done to evaluate nanoparticles size distribution, morphological behaviour, functional group entities and degree of crystallinity of prepared beads. The nanocomposite beads adsorption performance was investigated for malachite green (MG) dye and BET analysis were also recorded to know about porous behaviour of the nanocomposite beads. Maximum removal of malachite green (MG) dye was found to be 72.0 mg/g for 100 ppm initial dye concentration. For accurate observations linear and non-linear modelling was done to know about the best-fitted adsorption model during the removal mechanism of dye molecules, on evaluating it has been observed that Langmuir isotherm and Freundlich isotherm show best-fitted observation in the case of linear and non-linear isotherm respectively (R2 = 0.96 & R2 = 0.957). In the case of kinetic linear models, the data was well fitted with pseudo-second-order showing chemosorption mechanism (R2 = 0.999), and in the case of non-linear kinetic model pseudo first order showed good fit showing physisorption mechanism during adsorption (R2 = 0.999). The thermodynamic study showed positive values for ΔH° and ΔS° throughout the adsorption process respectively, implying an endothermic behaviour. In view of cost effectiveness, desorption or regeneration study was done and it was showed that after the 5th cycle, the removal tendency had decreased from 48 to 38 % for 20–100 ppm dye solution accordingly. Thus, nanocomposite beads prepared by the coagulation method seem to be a suitable candidate for dye removal from synthetic wastewater and may have potential to be used in small scale textile industries for real wastewater treatment.

Removal of a model reactive azo dye from aqueous solution by a bioadsorbent in batch and fixed-bed column modes: Application of the developed technology to a textile wastewater

Sugarcane bagasse (SB) was used to produce a new bioadsorbent (STEA), drawing on circular economy concepts. STEA was synthesized using a two-step one-pot reaction, employing epichlorohydrin and triethylamine in the presence of N,N-dimethylformamide, without the use of a petroleum-based catalyst. The structure and surface of STEA were characterized by elemental C, H, N, and Cl analysis, X-ray diffraction, infrared spectroscopy, 13C solid-state nuclear magnetic resonance spectroscopy, thermogravimetric analysis, specific surface area and pore size distribution determination, and point of zero charge measurement. Batch adsorption and desorption tests were performed with the model dye Remazol Golden Yellow (RGY) RNL, a reactive anionic azo dye widely used in textile industry, to evaluate the potential reuse and application of STEA in a fixed-bed column for wastewater treatment. For batch adsorption, the best dose and agitation speed were 0.2 g L−1 and 50 rpm, respectively. STEA effectively removed RGY over a wide range of pH (2.00–10.00). The equilibrium time, maximum adsorption capacity (Qmax), and desorption efficiency (Edes) were 720 min, 369 mg g−1 (0.71 mmol g−1), and 49.5 %, respectively. The fixed-bed column fed with a spiked aqueous RGY solution could be operated for 415 min, with Qmax of 422 mg g−1 (0.81 mmol g−1) and Edes of 58.9 %. Batch and continuous experiments using real textile industry wastewater containing reactive azo dyes showed high color removal efficiency by STEA, with no interference of other compounds present in wastewater on adsorption of the reactive azo dyes (overshooting effect). The technology was validated in a relevant environment and achieved technology readiness level 5, showing potential to be upscaled. Therefore, STEA proved to be an efficient bio-based technology for application in tertiary treatment of real textile plant wastewater to remove reactive anionic azo dyes.

Characteristics and performance of aerobic granular sludge technology in the treatment of real batik textile wastewater

Characteristics and performance of aerobic granular sludge technology in the treatment of real batik textile wastewater

Treatment of textile industry effluents with up‐flow anaerobic sulfidogenic reactor

AbstractBACKGROUNDDyes present in textile wastewater can pose various environmental problems, including toxicity, carcinogenicity and mutagenicity, when released into receiving environments. Sulfidogenic bacteria play a crucial role in wastewater treatment by reducing sulfate and producing sulfide through the utilization of organic compounds in water. The resulting sulfide often transfers its electrons to another electron acceptor. This study focused on the treatment of real textile wastewater using an up‐flow sulfidogenic column bioreactor.RESULTSThe reactor was acclimated to sulfate‐reducing conditions when influent chemical oxygen demand and sulfate concentrations were 1742 and 2000 mg L−1, respectively. Subsequently, a gradual transition was made from sulfate‐reducing conditions to dye‐reducing conditions. Throughout the study, the hydraulic retention time was maintained at 1 day.CONCLUSIONThe influent dye concentration was 2722 Pt‐Co, and an impressive dye removal efficiency of approximately 90 ± 2% was achieved. This corresponds to a removal rate of 2450 Pt‐Co L−1 day−1. Although the sulfide concentration in the reactor decreased in the last period, investigating the extent to which this sulfide participates in the dye removal may expand the use of sulfidogenic reactors in the treatment of real textile industry wastewater. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

A single-stage MABR reactor in the post-treatment of poultry slaughterhouse wastewater: nitrogen removal and microbial community

ABSTRACT The deammonification process is an efficient alternative to remove nitrogen from wastewater with a low carbon/nitrogen ratio. However, the reactor configuration and operational factors pose challenges for applications in treatment systems to remove nitrogen from municipal and industrial wastewater on a large scale. To address this gap, this study evaluated a new deammonification strategy using a single-stage membrane aerated biofilm reactor (MABR), operated with continuous flow, under different hydraulic retention times (HRT) in the post-treatment of poultry slaughterhouse wastewater with a low nitrogen load, similar to domestic wastewater. The performance of the MABR reactor and the microbial community was evaluated over a long period at HRTs of 12, 24, and 36 hours, corresponding to nitrogen volumetric loads of 181.0 g N.m−3.d−1, 87.4 g N.m−3.d−1 and 67.8 g N.m−3.d−1. The results show that total nitrogen (TN) removal and the microbial community in the MABR reactor were influenced by changes in HRT. The highest efficiency in TN removal was obtained with an HRT of 24 hours, in which the maximum TN removal efficiency was 77.04%. Candidatus Brocadia and Candidatus Jettenia were the two genera of bacteria with Anammox activity present in the reactor, with relative abundances of 7.27% and 0.74%, respectively. This study helps to deepen the understanding of the application of the single-stage MABR reactor in real wastewater treatment with a low nitrogen load.

Enhanced treatment performance and reduction of antibiotic resistance genes of biochar-aeration vertical flow constructed wetland for treating real domestic wastewater

Constructed wetlands (CWs) are widely utilized for domestic wastewater treatment, yet there is a relative scarcity of research focused on the treatment of real domestic wastewater. This study evaluated the enhanced treatment performance and nitrous oxide (N2O) emissions in CWs by integrating biochar with intermittent aeration, the removal of antibiotic resistance genes (ARGs) was also assessed. The results indicated that the biochar-aeration CW significantly improved denitrification, achieving a total nitrogen removal efficiency of 42.83 %. Notably, biochar-aeration CW exhibited the lowest N2O emission fluxes (31.28–726.49 μg m−2 h−1). Furthermore, the introduction of biochar fostered the development of tightly bound extracellular polymeric substances, primarily attributed to biofilm production. The biochar-aeration CW effectively reduced the four targeted ARGs (sul-I, sul-II, tet-O, tet-W) by 0.41–1.43 log. These findings would be beneficial for understanding the function of biochar-intermittent aeration technology in enhancing the treatment capacity of CWs for domestic wastewater treatment.

Treatment of real wastewater from a paper mill with combined treatment of electrochemical oxidation and ultrasonic irradiation

This study presents the effect of combined treatment of ultrasonic irradiation (UI) and electrochemical oxidation (EO) on real wastewater from a paper mill. Firstly, wastewater was treated with UI and EO separately and then it was treated with UI and EO together. Separate UI treatment of wastewater was able to achieve COD and color reduction by 40 % whereas the separate EO treatment was able to achieve COD and color reduction by 70–90 % (depending upon the combination of various parameters like current density, electrolyte concentration, pH, magnetic stirrer speed). However, when both processes were combined, they were able to achieve 100 % reduction of COD and color and that too in very less operation time (less than 80 min). Platinum coated titanium (Pt/Ti) sheet was used as anode and stainless steel sheet as cathode. Combined treatment was carried out at optimal conditions derived from separate EO treatment. These optimal conditions were 6 mA/cm2 current density, 1.5 gm/l NaCl concentration, 6 pH, and 400 rpm magnetic stirrer speed. UI not only provided an alternative way of creating turbulence but also helped in decomposing the pollutants by weakening their bonds. Moreover, it was found that energy consumption in combined UI and EO treatment is much less than the energy consumption in separate EO treatment with magnetic stirrer.

Evaluation of batch and fed-batch rotating drum biological contactor using immobilized Trametes hirsuta EDN082 for non-sterile real textile wastewater treatment

White rot fungi, in both free and immobilized forms, excel in degrading dyes through adsorption and enzyme degradation. However, existing studies often focus on synthetic wastewater within sterile lab conditions. This study extends the application of Trametes hirsuta EDN082 immobilized in light-expanded clay aggregates (myco-LECAs) packed in a rotating drum biological contactor (RDBC) for treating real textile wastewater under non-sterile conditions to simulate industrial treatment scenarios. Experiments included batch and fed-batch RDBC to assess the impact of additional glucose and stepwise dilution on quality indicators like pH, chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), color, and solids. In fed-batch RDBC with 0.5 % additional glucose, myco-LECAs achieved a maximum of 94 % COD removal (day 15), 99 % NH4+-N reduction (day 33), and 39 % decolorization without additional glucose. In comparison, myco-LECAs in batch RDBC highlighted 89 % NH4+-N reduction in 9 days without pH adjustment or additional nutrients. The pH maintained between 6−9, with no toxicity in Artemia salina, and 97−100 % removal of E. coli. Compared to Indonesian textile wastewater discharge limits, the technology achieved effective ammonia removal below 8 mg/L. This suggests that immobilized T. hirsuta EDN082 in LECAs presents a viable, non-sterile treatment for real textile wastewater.

Efficient treatment of secondary treated refinery wastewater using sand biofiltration: Removal of hazardous organic pollutants

This study explored the potential of sand biofiltration for tertiary treatment of real refinery wastewater. The biofilter (2 cm (I.D.) x 15 cm (L)) operated on secondary treated refinery wastewater at flow rate of 1 mL/min had empty bed contact time (EBCT) of 47.12 min for one circulation. Maximum reduction in COD after 4, 8 and 12 times recirculation was 25 %, 52 % and 56 %; while the TOC reduction was 33 %, 43 % and 51 %, respectively, after biofilm development over 30 days. Quantification using two dimensional gas chromatography – time of flight mass spectrometry (GCxGC-TOF MS) revealed that several of the identified target compounds could not be detected in the wastewater after 12 recirculations. After 8 times recirculation, most of the compounds showed very high removal efficiency. For biofiltration over the flow rate range 2–10 mL/min, the reduction in COD and NH4+-N ranged from 62–73 % and 78–86 %, respectively, after 8 times recirculation. The nitrite concentration first increased and subsequently decreased, while the nitrate concentration continuously increased with increase in the number of recirculations. Solid phase micro-extraction (SPME) analysis of the aqueous phase using GCxGC-TOF MS and a semi-quantitative approach indicated that the removal of predominant classes of compounds was greater than 95 % after 8 times recirculation, with maximum reduction occurring in the first pass through the biofilter. Assimilable organic carbon (AOC) reduction was 98 % after 8 times recirculation. Metagenomic analysis revealed that Proteobacteria was the most dominant phylum in the biofilter. Many known polynuclear aromatic hydrocarbon (PAH) degraders, such as Sphingomonadales, Burkholderiales, Rhodobacterales and Rhodospirillales, were found in the biofilter leading to high removal efficiency of hazardous organic pollutants.

Persulphate assisted photoelectrochemical degradation of organic pollutants in water on a silver nanoparticle modified Cu2O photoanode

This work presents the photoelectrochemical production of sulphate radicals using fluorine-doped tine oxide – silver nanoparticles – copper(I) oxide (FTO-AgNPs-Cu2O) photoanode in the presence of peroxydisulphate salt for the enhanced degradation of selected organic pollutants in water. Firstly, Cu2O was prepared via a facile and template-free one-pot method, then AgNPs were photo-reduced on the surface of the Cu2O, and the resultant product was immobilised on an FTO conductive substrate to form FTO-AgNPs-Cu2O photoanode. When the electrode was applied for the abatement of tetracycline in the presence of 3 mM peroxydisulphate salt and 1.5 V external potential, the degree of tetracycline degradation and mineralisation after 90 min was 82 % and 78 % respectively. Furthermore, the same system was able to achieve degradation of 81 % sulfamethoxazole degradation within 90 min and 100 % orange II dye degradation within 30 min. The photoanode was efficient in the treatment of real wastewater containing tetracycline. Scavenger studies reveal that holes, hydroxyl, and sulphate radicals significantly participated in the degradation process. The electrode is stable and therefore applicable for the abatement of other organic pollutants in a persulphate-assisted photoelectrochemical degradation system.

Short-term electrochemical stimulation induces sustained enhancement of extracellular pollutant degradation in anaerobic granular sludge

Electroactive bacteria (EAB) are advantageous for degrading the pollutants extracellularly, but the enrichment primarily restricts on the electrode surface of bioelectrochemical system and is challenging to scale up. To address this, a new strategy was proposed to electrochemically stimulate the anaerobic granular sludge (AGS) and employ the harvested electroactive granular sludge (EGS) to an electrode-free bioreactor for pollutant removal. Fast establishment of EGS was achieved after 7 days' electrochemical stimulation, with a maximum current output of 112.5 A/m3 achieved and the abundance of electroactive bacteria-like genera increased from 5% to around 20%. The electric conductivity of EGS improved by 1-fold, while the increased extracellular protein and humic acid substance but unchanged polysaccharide content in the extracellular polymeric substance suggested a more robust redox network. After assembling in a sequential batch reactor, the methylene orange (MO) and Cr(VI) removal rate by EGS was enhanced by 65–80% and 38–55%, respectively. Better oxygen tolerance was also observed. The comparative study with exogenous riboflavin and respiration inhibitors indicated the complete extracellular reduction achieved by EGS while almost half of MO was metabolically degraded by AGS, which was kinetically sluggish. More importantly, there is no performance and electroactivity decay in a 60 days' batch operation. Meanwhile, the characterization of microbial community revealed the further increased abundance of EAB-like genera (∼28%) but Acinetobacter became dominant (∼15%), suggesting the competition of EAB species in EGS. In brief, a simple 7-day electrochemical stimulation imposed diverse and sustained benefits on the performance and microbial community of granular sludge, which may inspire the application of EAB and their extracellular degradation capacity in real wastewater treatment.

Magnetic coagulant derived from Cassia fistula seed for real textile wastewater treatment: A pilot-scale study

Cassia fistula (C. fistula) seed-derived coagulants have demonstrated substantial potential for treating dye-based wastewater. Such coagulants exhibit notable coagulating-flocculating activity and are environmentally friendly. However, recovering these natural coagulants from aqueous media poses challenges. In this study, we introduce a novel plant-derived magnetic coagulant that is a combination of C. fistula seed gum with magnetic spinel ferrite. This research includes a pilot-scale study to simulate full-scale textile wastewater treatment using this composite. Material characterisations revealed that spherical CoFe2O4 particles could be effectively coated with the active coagulant, C. fistula gum. The saturation magnetisation of the composite, measured at 54.11 emu/g, facilitates its convenient separation from aqueous solutions using an external magnetic field. Bench-scale studies showed that initial pH and coagulant dosage substantially affect the removal efficiency of colour and chemical oxygen demand (COD). In the pilot-scale study, the C. fistula–CoFe2O4 composite demonstrated promising coagulant properties. It achieved a colour removal percentage of 94.0 % with a volume of 30 L and a coagulant dosage of 12.3 g L− 1. Using this coagulation–flocculation process as a primary treatment step, possibly followed by biological or membrane methods, can help meet Vietnamese environmental standards.

Treatment of pharmaceutical industry wastewater for water reuse in Jordan using hybrid constructed wetlands

Developing cost-efficient wastewater treatment technologies for safe reuse is essential, especially in developing countries simultaneously facing water scarcity. This study developed and evaluated a hybrid constructed wetlands (CWs) approach, incorporating tidal flow (TF) operation and utilising local Jordanian zeolite as a wetland substrate for real pharmaceutical industry wastewater treatment. Over 273 days of continuous monitoring, the results revealed that the first-stage TFCWs filled with either raw or modified zeolite performed significantly higher reductions in Chemical Oxygen Demand (COD, 58 %–60 %), Total Nitrogen (TN, 32 %–37 %), and Phosphate (PO4, 46 %–64 %) compared to TFCWs filled with normal sand. Water quality further improved after the second stage of horizontal subsurface flow CWs treatment, achieving log removals of 1.09–2.47 for total coliform and 1.89–2.09 for E. coli. With influent pharmaceutical concentrations ranging from 275 to 2000 μg/L, the zeolite-filled hybrid CWs achieved complete removal (>98 %) for ciprofloxacin, ofloxacin, erythromycin, and enrofloxacin, moderate removal (43 %–81 %) for flumequine and lincomycin, and limited removal (<8 %) for carbamazepine and diclofenac. The overall accumulation of pharmaceuticals in plant tissue and substrate adsorption accounted for only 2.3 % and 4.3 %, respectively, of the total mass removal. Biodegradation of these pharmaceuticals (up to 61 %) through microbial-mediated processes or within plant tissues was identified as the key removal pathway. For both conventional pollutants and pharmaceuticals, modified zeolite wetland media could only slightly enhance treatment without a significant difference between the two treatment groups. The final effluent from all hybrid CWs complied with Jordanian treated industry wastewater reuse standards (category III), and systems filled with raw or modified zeolite achieved over 95 % of samples meeting the highest water reuse category I. This study provides evidence of using hybrid CWs technology as a nature-based solution to address water safety and scarcity challenges.

The development and application of Cu@TiO2@SAPO-34 as better photocatalyst towards degradation of various pollutants

The study developed a novel Cu@TiO2@SAPO-34 nanocomposite for photocatalytic mortification of organic pollutants using modified hydrothermal synthesis. The material was characterized using XRD, BET, XPS, SEM, TEM, UV–vis, and Photoluminescence spectroscopy, confirming high pollutant absorption and photocatalytic capability. The structural analysis identified the emergence of monoclinic CuO and pure anatase phase TiO2, with ligands matching the formation of SAPO-34 at various planes of 2theta degrees. Also, species of Cu-SAPO-34 (35.43 and 65.88°) and TiO2-SAPO-34 (25.56°) were identified. The BET analysis indicated a narrow pore size distribution of 5.59 nm for Cu@TiO2@SAPO-34, with a high surface area to volume ratio of 145.7868 m2. g−1. The optical property analysis revealed that TiO2 exhibited light absorption mainly in the visible region, while Cu@TiO2@SAPO-34 exhibited early adsorption in the ultraviolet region and extended to the visible regions. This was accompanied by a concomitant decrease in band gap energy from 3.09 eV for TiO2 to 2.61 eV for Cu@TiO2@SAPO-34. The Photodegradation experiment demonstrated that TiO2 nanoparticles achieved 83 % degradation of methylene blue (MB) dye solution after 120 minutes under ultraviolet irradiation, while the Cu@TiO2@SAPO-34 composite achieved 98 % within 30 minutes. The novel nanocomposite material was further tested for real wastewater treatment, self-cleaning of the coated film, and nature of wettability, which all confirmed that the novel Cu@TiO2@SAPO-34 composite is superhydrophilic and a better photocatalyst for degrading organic contaminants. The study details the Photodegradation reaction mechanism for the Cu@TiO2@SAPO-34 nanocomposite, comparing it to TiO2 under UV–vis irradiation, and proposes a chabazite-related structure using Biovia Materials Studio 2020.

Energy-efficient treatment of refractory industrial effluent using flow-through electrochemical processes: Oxidation mechanisms and reduction of chlorinated byproducts

While flow-through anodic oxidation (FTAO) technique has demonstrated high efficiency to treat various refractory waste streams, there is an increasing concern on the secondary hazard generation thereby. In this study, we developed an integrated system that couples FTAO and cathodic reduction processes (termed FTAO-CR) for sustainable treatment of chlorine-laden industrial wastewater. Among four common electrode materials (i.e., Ti4O7, β-PbO2, RuO2, and SnO2-Sb), RuO2 flow-through anode exhibited the best pollutant removal performance and relatively low ClO3 and ClO4 yields. Because of the significant scavenging effect of Cl− in real wastewater treatment, the direct electron transfer process played a dominant role in contaminant degradation for both active and nonactive anodes though active species (i.e., active chlorine) were involved in the subsequent transformation of the organic matter. A continuous FTAO-CR system was then constructed for simultaneous COD removal and organic and inorganic chlorinated byproduct control. The quality of the treated effluent could meet the national discharge permit limit at low energy cost (∼4.52 kWh m3 or ∼0.035 kWh g1-COD). Results from our study pave the way for developing novel electrochemical platforms for the purification of refractory waste streams whilst minimizing the secondary pollution.