Color Removal Research Articles

Enhanced Removal of Refractory Organic Compounds from Coking Wastewater Using Polyaluminum Chloride with Coagulant Aids

This study explores the enhanced removal of refractory organic compounds from coking wastewater using polyaluminum chloride (PACl) with two different basicity levels (0.5 and 2.5), in combination with coagulant aids such as cationic polyacrylamide (CPAM) and iron ions. The results demonstrated that both PACl formulations significantly outperformed commercial PACl in terms of COD and color removal, with PACl at the basicity of 2.5 achieving slightly higher efficiency than PACl at the basicity of 0.5. The improved performance was attributed to the higher content of polymeric aluminum species, enhancing charge neutralization and bridging adsorption. The addition of coagulant aids further improved the performance, with PACl at the basicity of 2.5 combined with iron ions achieving the highest COD (48.41%) and color removal (80.77%), due to sweep coagulation and complexation. Organic composition analysis using gas chromatography–mass spectrometry (GC-MS), three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy, and ultraviolet (UV) spectroscopy indicated that PACl combined with iron ions was the most effective in removing polycyclic aromatic hydrocarbons (PAHs) and nitrogen-, oxygen-, and sulfur-containing heterocyclic compounds. Additionally, a floc analysis showed that the flocs formed with iron ions were more compact and had better settleability compared to those formed with CPAM, further contributing to the improved coagulation efficiency. These results highlight the importance of optimizing the PACl basicity and coagulant aid selection for the enhanced removal of refractory organic compounds from coking wastewater, offering a promising strategy for advanced wastewater treatment.

Dual approach in textile wastewater treatment: optimisation and comparison of fluidised-bed and conventional Fenton processes

ABSTRACT This study optimises secondary textile dyeing wastewater removal using fluidised-bed Fenton (FBR-Fenton) and standard Fenton processes for chemical oxygen demand (COD) and colour removal efficiency. The Box–Behnken response surface approach optimised pH, iron ion concentration, and hydrogen peroxide concentration. At pH 3.3, [Fe2+] = 2.6 mm, [H2O2] = 6.4 mm in the fluidised bed reactor with 67 g/L quartz sand, with a 50% bed expansion after 40 min, the FBR-Fenton process removed 75.8% COD and 98.0% colour. The standard Fenton method was tuned to pH 3.2, [Fe2+] = 3.1 mm, [H2O2] = 6.6 mm, and COD and colour removal effectiveness of 69.7% and 97.5%, respectively. FBR-Fenton enhanced COD and total iron removal efficiency, reduced chemicals, and reduced sludge by 28.0% compared to conventional Fenton. This study also showed quartz sand reusability in FBR-Fenton treatment cycles. Experimental results matched response surface model predictions, proving regression equation correctness.

Performance of a novel Built-in Static Magnetic Field – Biological Aerated Filter (BSMF–BAF) for treating high-salt textile dyeing wastewater

High-salt textile dyeing wastewater is difficult to treat. Magnetic fields can enhance the biodegradation capacity and extreme environmental adaptabilities of microorganisms. Thus, magnetically enhanced bioreactors are expected to improve the treatment efficiency and stability of high-salt textile dyeing wastewater. Accordingly, a novel Built-in Static Magnetic Field – Biological Aerated Filter (BSMF–BAF) was constructed and investigated for treating actual high-salt textile dyeing wastewater in this study. Two other BAFs packed with traditional and magnetic ceramsite carriers, respectively, were simultaneously operated for comparison. The removal of color, chemical oxygen demand (COD), suspended solid (SS) and acute toxicity were monitored. The activities of key enzymes and microbial community structure were analyzed to reveal possible mechanisms for improving the treatment efficiency of traditional BAF using the BSMF. The results showed that the BSMF–BAF possessed the highest removal efficiencies of color, COD, SS and acute toxicity among the three BAFs. The BSMF induced significant increases in the activities of azoreductase and lignin peroxidase, which were responsible for the degradation of azo compounds in the wastewater and the detoxification of toxic intermediates, respectively. Additionally, the BSMF induced the relative enrichment of potentially effective bacteria and fungi, and it maintained a relatively high abundance of fungi in the microbial community, resulting in a high treatment efficiency.

Experimental investigation and Monte Carlo simulation of landfill leachate treatment using physicochemical method and a non-thermal plasma reactor

ABSTRACT Leachate treatment is one of the challenging subjects in the field of waste management. Leachate as a dumpling sites hazardous byproduct due to the high concentration of chemical oxygen demand (COD) and toxic compounds with dark colour is a potential pollutant of the environment, causing a lot of problems in the absence of treatment and direct discharge to the environment. In this study, the combinatory performance of sequential chemical flocculation and coagulation process and non-thermal plasma (NTP) technology on leachate from the Sarāvān city former controlled landfill, Iran, was investigated. The outcomes of Jar test illustrated that hydrated aluminium sulphate (PAC) was selected the best coagulant compared with hydrated aluminium sulphate (HAS) and ferric chloride (FC) to remove suspended solids and colour. The optimised parameters for 10% PAC pre-treatment were obtained 3 g lime and cationic 0.1 g polyelectrolyte per 1 litre of leachate. After pre-treatment by using jar test, NTP was used to remove turbidity, colour, COD and so forth. The sequential system-based all stages of pretreatment and NTP diminished the turbidity and colour removal to 98.6% and 99.2%, respectively. Furthermore, COD, BOD5, TSS, and TDS were also reduced. As a result, combination of pre-treatment and NTP technology are able to remove the landfill leachate effectively. Monte Carlo calculations exhibited that Al3+ and H2O2 had the most effects to decompose HA (Humic acid) compound in physicochemical pre-treatment and treatment stages.

Optimization of the use of Moringa oleifera in wastewater treatment by rotational central composite design

Textile effluents have a complex waste composition due to the various compounds present and their resistance to degradation. Given the harmful effects of these pollutants on aquatic ecosystems, adequate treatment before disposal is essential, usually involving chemical processes such as coagulation and flocculation. This study optimizes textile wastewater treatment using Moringa oleifera as a natural coagulant through Rotational Central Composite Design (RCCD), a type of Response Surface Methodology (RSM), aiming to improve color removal, a key factor for effluent quality. By exploring Moringa oleifera as a sustainable alternative, the research provides new insights into environmentally friendly coagulant use and treatment optimization. The treatment’s effectiveness depends on the coagulant dosage, the energy applied, and the pollutant concentration. Dye removal was evaluated using spectrophotometry, and the evaluated factors in the optimization process were slow and fast mixing times, coagulant dosage, and pollutant concentration. The study identified pollutant concentration and slow mixing time as the most influential factors in treatment effectiveness. The model achieved a coefficient of determination (R²) of 87.9 %, and maximum dye removal reached 80.2 % under optimal conditions: 30 mL of coagulant, 20 min of slow mixing, 2 min of fast mixing, and a pollutant concentration of 300 mg ∙ L−1. The average removal efficiency was 47.86 %, indicating that natural coagulants offer a viable alternative for textile effluent treatment.

Down flow jet-loop reactor with NF-RO membrane system for the treatment of textile wastewater

Textile industries are significant consumers of fresh water, extensively using it for washing and dyeing processes. The effluent from these operations contains various chemicals, including complex synthetic dyes, NaCl and Na2SO4 necessitating efficient treatment before discharge into water bodies. Zero Liquid Discharge (ZLD) technology facilitates complete water recovery but leads to substantial solid waste accumulation, which poses challenges for reutilization. This study introduces an innovative approach using a Downflow Jet Loop Reactor combined with ozone and activated carbon to effectively remove color and Chemical Oxygen Demand (COD) from textile effluent. Furthermore, a combination of Nanofiltration (NF) and Reverse Osmosis (RO) membrane systems ensures comprehensive purification by effectively separating inorganic salts. Experimental results demonstrated a maximum color removal of 81.25 % from the textile effluent. The fabricated PSF/PVDF NF membrane exhibited exceptional capacity for rejecting divalent salts. Additionally, the RO reject, which is a concentrated solution of salts and contaminants, was successfully reused in a dye bath for cotton fabric dyeing. This approach highlights the practicality, sustainability, and resource conservation potential within the textile production cycle. It underscores the importance of a comprehensive water treatment strategy for achieving sustainable textile production.

Treatment of bio-treated coking wastewater in a 3DEF system with Fe-loaded needle coke particle electrodes

As one of the most representative hard-to-biodegrade industrial wastewater, coking wastewater is poor in biodegradability and has a high concentration of organic matter. Consequently, even after treatment using biochemical technology, the discharge standards cannot be reached. We used the self-developed Fe-loaded needle coke electrodes (Fe-NCPEs) as particle electrodes and established a three-dimensional electro-Fenton (3DEF) system for the treatment of bio-treated coking wastewater (BTCW) in this study. The 3DEF system's conditions for treating BTCW were optimized using Response Surface Method (RSM). When the initial pH was 4.69, the applied voltage was 11.1 V, the Fe-NCPE dosage was 11.63 g L−1, and the COD was reduced from 387 to 57.3 mg L−1 and the colour removal rate reached 99 % after 3 h of reaction, meeting local coking wastewater discharge standards. The power consumption is only 15 kWh per ton of BTCW, indicating that this system can treat the BTCW with high efficiency and low energy consumption. UV-Vis, FTIR, and GC-MS analysis illustrated that cyclic aromatic compounds, esters, and ethers can be efficiently degraded to alkanes and olefins by the 3DEF system. The ·OH quenching experiments showed that in the 3DEF system, the ·OH is the main reactive group, which can oxidize the large hard-to-degrade organic compounds in BTCW to small organic compounds, and even to CO2 and H2O. Dynamic experiments showed that the 3DEF system can successfully remove pollutants from BTCW under continuous flow conditions with an HRT of 3 h, allowing it to meet emission standards.

Eco-benevolent synthesis of ZnO-NPs and ZnO-MFs from Inula oculus-christi L. (Asteraceae) with effective antioxidant, antimicrobial, DNA cleavage, and decolorization efficiencies.

As a result of the changes occurring globally in recent years, millions of people are facing challenging and even life-threatening diseases such as cancer and the COVID-19 pandemic, among others. This phenomenon has spurred researchers towards developing and implementing innovative and environmentally friendly scientific methods, merging disciplines with significant technological potential, such as nanotechnology with medicinal plants. Therefore, the focus of this research is to synthesize zinc nanoparticles (ZnO-NPs) and microflowers (ZnO-MFs) using extracts of the medicinal plant I. oculus christi prepared in n-hexane and methanol as new bioreduction and capping agents through a simple and environmentally friendly chemical approach. Optical, thermal, and morphological structural analyses of ZnO-NPs and ZnO-MFs were conducted using Ultraviolet-Visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FT-IR) spectroscopy, Thermogravimetric Analysis (TGA), and Field Emission Scanning Electron Microscopy (FE-SEM). Metabolic profiles of extracts from different plant parts were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) and supported by visualization of contents through Principal Component Analysis (PCA), hierarchical cluster analysis heatmaps, and Pearson correlation graphs. Interestingly, ZnO-NPs and ZnO-MFs exhibited strong antioxidant properties and demonstrated particularly potent antimicrobial activity against Micrococcus luteus NRRL B-4375, Escherichia coli ATCC 25922, and Candida albicans ATCC 10231 strains compared to standard antibiotics. Furthermore, ZnO-NPs and ZnO-MFs showed excellent plasmid DNA-cleavage activity of pBR322 with increasing doses. The photocatalytic performance of the synthesized ZnO-NPs and ZnO-MFs was evaluated for methylene blue (MB), congo red (CR), and safranin-O(SO) dyes, demonstrating remarkable color removal efficiency. Overall, the results provide a promising avenue for the green synthesis of ZnO-NPs and ZnO-MFs using I. oculus-christi L. inflorescence and pappus extracts, potentially revolutionizing biopharmaceutical and catalytic applications in these fields.

Effective removal of different dyes using run-of-mine and processed coal samples

Coal, traditionally utilised solely for combustion, is now being investigated for its potential as an adsorbent in purifying drinking water by eliminating hazardous metal ions. Limited research exists regarding its effectiveness in reducing organic dye levels. Presented here are the outcomes of an extensive investigation into various carbon samples' efficacy as adsorbents for wastewater color removal. Samples of coal sourced from Western Coalfield Limited (WCL) were meticulously processed and characterized, encompassing run-of-mine coal and acid-leached coal. A comprehensive array of techniques, including scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, was employed for coal characterization. Proximate analysis and gross calorific value (GCV) were employed to assess coal's physical attributes. The adsorption behavior of methylene blue (MB) and crystal violet (CV) on coal was scrutinized, varying factors such as contact time, pH, initial MB and CV concentrations, and adsorbent doses. Optimal adsorption parameters for MB were determined as pH 2, initial concentration of 1 ppm, 0.2 g adsorbent dose, and 60 min contact time. For CV, optimal conditions were pH 8, initial concentration of 6 ppm, 0.4 g adsorbent dose, and 45 min contact time. MB adsorption kinetics favored the pseudo-second-order reaction model, with Freundlich isotherms providing a better fit than Langmuir isotherms. Conversely, CV adsorption kinetics favored the pseudo-second-order reaction model, with Langmuir isotherms exhibiting a superior fit compared to Freundlich isotherms.

Effect of chromophore type on efficiency of reactive dye removal using polyamidoamine dendrimer

AbstractIn this study, by selecting a sample of dyes from a wide variety of chromophores used in the production of reactive dyes (monoazo, bisazo, metal azo, phthalocyanine, anthraquinone, copper formazan and triphendioxazine), the colour removal performance of polyamidoamine (PAMAM) dendrimer in reactive dyes was statistically evaluated depending on the dye chromophore groups (and accordingly molecular weight and number of sulfo groups of the dye), dendrimer concentration and centrifugation time. When all the results were examined, it was observed that the colour removal efficiency was significantly lower in metalazo and copper formazan‐based reactive dyes, whereas colour removals ranging from 93% to 98% could be obtained in bisazo, triphendioxazine, monoazo, anthraquinone and phthalocyanine dyes. With the use of dendrimer, the best colour removal efficiencies occurred at pH 3. However, it was found that the centrifugation time of 15 min is sufficient for all dyes, and a longer centrifugation does not provide any additional benefit in terms of colour removal.

Reuse and Recovery of Water from Industrial Textile Dyeing Effluent Using High-Performance Electrodes Continuous Flow Electrocoagulation Reactor

The dye effluents released from the textile and printing industries contain strong colorants, inorganic salts, and other toxic compounds. The conventional coagulation technique of dye effluent treatment is plagued with issues of low removal rate of color, generation of large quantities of sludge, and toxic end-products. Recently electrocoagulation technique gained immense attention due to its high efficiency. This technique involves the dissolution of the sacrificial anodes to provide an active metal hydroxide as a strong coagulant that destabilizes the pollutants and removes them by precipitation or flocculation. This study is about the efficiency of the electrocoagulation process using titanium coated - aluminum and mild steel electrodes to treat industrial dye wastewater. Effects of parameters such as current density & initial dye concentration were investigated. It was observed that, for the same current density, electrode consumption was higher with TiO2/Al electrode than with mild steel electrode, resulting in more color removal efficiency (CRE) using TiO2/Al electrode. The settling rate of the flocs was higher in the rector having TiO2/Al electrode at the 100 mL with current density (2.5 mL.min-1 to 5.3 mL.min-1), while in the reactor with mild steel electrode, the settling rate was very less. The results showed that dye removal was 95.11% and 92.1% for mild steel and titanium-coated electrodes, respectively. It was observed that 50 % of Aluminum was removed from the treated effluent after the final stage of filtration. Based on the multicriteria analysis to identify the optimum operational parameters to be applied at the field level, it was observed that maximum CRE may be obtained with TiO2/Al electrode and the applied current of 1 Amps with a flow rate of 100 mL.min-1. It can be concluded that electrocoagulation is a highly efficient and the fastest method to treat dye effluents from industries.

A comparative study of ferrous and persulfate catalysts for the H2O2/UV oxidation of batik wastewater

The increasing number of batik industries in Indonesia may lead to water pollution due to wastewater containing high levels of organic pollutants. This study evaluated advanced oxidation processes (AOPs) utilising H2O2/UV to decolourise and remove organic contaminants (measured as chemical oxygen demand, COD) from batik wastewater. The study aims to compare the effectiveness of adding ferrous and persulfate as catalysts as catalyst in the H2O2/UV process, specifically evaluating the H2O2/Fe2+/UV and H2O2/S2O82-/UV processes. The results indicated that all treatment methods effectively decolourised and degraded COD in the batik wastewater. COD and colour removal achieved up to 96.51% and 78.70% for H2O2/UV, 97.20% and 83.53% for H2O2/Fe2+/UV, and 97.20% and 83.53% for H2O2/ S2O82-/UV, processes, respectively. Additionally, the use of persulfate as a catalyst accelerated the oxidation processes, reaching completion in 45 minutes compared to 60 minutes with the other catalyst.

Effect of electrooxidation pretreatment on treatment efficiency, membrane fouling and microbial community of a membrane bioreactor treating sludge dewatering wastewater

This study investigated electrooxidation (EO) pretreatment for sludge dewatering wastewater and condensate generated during the process, aiming to enhance its treatment via a membrane bioreactor (MBR) and prevent membrane fouling. EO treatment could achieve a complete suspended solids (SS) removal along with 97.4 % EPS and 90.1 % colour removal under the optimum conditions. However, the NH4+-N and total organic carbon (TOC) concentration in wastewater increased (16 % and 72.8 %, respectively) due to break down of the complex organic substances present in the wastewater. MBR treating EO pretreated wastewater showed significant improvement against membrane fouling, as shown by reduction in transmembrane pressure (TMP) from 15 kPa in control to 0 kPa in the experimental reactor. The MBR operated with EO-treated wastewater and a 16-day HRT resulted in a low effluent NH4+-N concentrations of 469.3 mg/L (74.9 % removal) along with a very low TOC concentration of 24.3 mg/L (98.7 % removal). The microbial community analysis revealed that enrichment of selected organic carbon degraders (Defluviitoga, Pedobacter, and Flavobacteriaceae) and nitrogen cycle bacteria (Dechloromonas, Comamonas, Arenibacter, Brevundimonas, Thauera, and Aequorivita), including some aerobic denitrifiers (Aquamicrobium and Chryseobacterium) in the experimental reactor treating EO-pretreated wastewater is responsible for enhancing microbial degradation and its overall performance.

Evaluation of the removal of cyanobacteria and cyanotoxins with a composite hydrogel based on chemically modified gelatin and PVA-containing graphene oxide nanoparticles

After being applied to pharmaceutics removal from water, the newly synthesized composite hydrogel based on chemically modified gelatin and PVA-containing graphene nanoparticles (CHGP-GOn), was now assessed for another application. The hydrogels were able to interact with Microcystis aeruginosa cells, resulting in the formation of small cell colonies and cell lysis related to exposure time. In the removal tests, the best general removal efficiency of cyanobacterial cells was achieved with the highest adsorbent mass at natural pH, achieving values of removal of 90 % for cells, 75 % chlorophyll-a, 63 % and 43 % for turbidity and visible colour removals, respectively. From the kinetic study, the results showed that cell inactivation has achieved removal equilibrium in 19 h, with a qe of 106 × 106 cells/g of CHGP-GOn. Furthermore, with the results from the other parameters, the tests presented a removal equilibrium of just 14 h, there was a removal of 4670 µg/L of Chlorophyll-a and 6450 µg/L/g of MC-LR microcystin per gram of adsorbent. The experimental data best fitted to the Elovich model, indicating possible removal by chemisorption. Analysis of cellular integrity and morphology showed that within just 12 h, few cyanobacterial cells showed membrane disruption and release of intracellular toxins, with an increase in the toxicity medium related to extended exposure time, and presentation of morphological and superficial cellular damage within 24 h. In addition, other characteristic measurements presented an exceptional mechanical strength and resistance that was slightly reduced after swelling. However, showing good development during adsorption tests under agitation, without any detachment of material and an absence of GO leaching. Therefore, it can be concluded that the synthesized hydrogel should be applied in removing M. aeruginosa cells and their toxins from water treatment, serving as an excellent alternative to traditional adsorbents.

Novel Bubble Column Design Constructed for Catalytic Ozonation – Effectiveness Assessment by Hydrodynamics and Kinetic Regime Determination

ABSTRACT This article introduces an innovative design for a bubble column tailored for catalytic ozonation. A semi-batch reactor was employed with strategically positioned baffles to accommodate catalysts throughout the column. These baffles, constructed with a specially designed mesh-type material, not only served as catalyst supports but also provided an additional active surface for efficient mass transfer on both macro and micro scales. This groundbreaking approach has advanced heterogeneous catalysis by utilizing a multi-structured scaffold enriched with chemically active species. The dual role of the baffles was envisioned to enhance the physical absorption of ozone gas into the liquid and catalytic action in the production of reactive oxygen species (ROS) through ozone decomposition. However, it is crucial to note that any alteration in the column’s geometry can influence the mass transfer resistance. The primary objective of this study was to assess the efficiency of the newly constructed bubble column by determining hydrodynamic parameters. For the column without mesh, the volumetric mass transfer coefficient (kLa) ranged between 0.007 and 0.009 1/s. Upon the incorporation of the mesh, kLa increased to values between 0.007 and 0.01 1/s. Simultaneously, the overall interphase surface rose from 42.16 ± 6.2 1/m to 53.29 ± 7.9 1/m, and the film mass transfer coefficient (kL) improved from (1.68 ± 0.1) × 10−4 to (2.13 ± 0.2) × 10−4 m/s after the mesh installation. This novel column design was specifically engineered for the treatment of textile wastewater. Dye degradation experiments demonstrated a higher rate of color removal when the mesh was inserted, surpassing traditional ozonation methods. Furthermore, the Hatta number increased from 3 to 5 with mesh usage, and the enhancement factor (E) shifted from 2.6 to 4. These enhanced Hatta values and improvement factors suggest that the new column construction successfully transitioned the operating regime from moderate to high speed.

Color, COD, and turbidity removal from surface water by using linseed and alum coagulants: optimization through response surface methodology

This study examined the treatment of surface water using a mixed natural (linseed) and chemical (alum)-based coagulant in terms of color, turbidity, and chemical oxygen demand (COD) (%) removal in a laboratory jar test. Experimental results showed that using a combined coagulant has shown higher removal of color (99.72%) and turbidity (97.76%) at pH values of 3.5 using a 1.5 g/L dosage and a stirring time of 38.58 min. Similarly, at the same pH value and 2.5 g/L dosage, the COD removal was 96%. To determine the optimum value with the highest percent removal efficiency of the coagulation–flocculation process, several experimental parameters including blended dosage, pH, COD concentration, and initial turbidity have been studied in terms of the percent of color, chemical oxygen demand, and turbidity removal. The optimum value was found for the highest removal of color-97.75%, turbidity-96.86%, and COD-90.33% with the pH values of 7.0, at a dosage of 2.5 g/L and a stirring time of 40 min, respectively. Statistical techniques of response surface methodology were used in experimental design and optimization, in order to calculate the confidence intervals to assess population parameter precision. An ANOVA-95% confidence interval ensures that the high reliability optimizes the result. The findings proved the excellent adsorption potential and high performance of the blended coagulant in the removal of contaminants from surface water.

Removal of Ammonia and Colour from Landfill Leachate using Integrated Electrocoagulation-Zeolite Adsorption Processes

The amount of waste generated in Malaysia had increased annually due to both economic and population accelerations. This resulted in an increase in leachate production that contains a high amount of ammonia nitrogen (NH3-N) and colour, which is a severe problem for both environments as well as for human health. Therefore, this study aimed to determine the potential of Electrocoagulation (EC) – zeolite adsorption for removing NH3-N and colour from landfill leachate. In the experimental works, two batch studies consist of batch EC using aluminium (Al) cylindrical electrode and batch adsorption study using clinoptilolite zeolites adsorbent were conducted using leachate sample collected from Pulau Burung Sanitary Landfill (PBSL). The batch EC experiment was carried out to determine the optimum removal of NH3-N and colour by the effect of current density (7 - 35 mA/mm2), initial pH (5 - 9), electrolysis time (0 - 90 minutes) and inter-electrode distance (5 - 25 mm). An integrated EC - zeolite adsorption was carried out under the optimum condition of 2.0 g/150 mL adsorbent dosage, contact time of 100 minutes and an initial pH value of 8. Based on the experiment, almost 50% of NH3-N and 95% of colour were removed using a single EC under the optimum current density of 14.0 mA/mm2, pH 5, electrolysis time of 75 minutes and 15 mm of inter-electrode distance. A comparison of colour removal between single EC and EC-Zeolite showed the same degradation performance. The interaction of hydrogen ion (H+) with aluminium hydroxide ion (Al (OH)3) produces during EC stabilises small particles forming larger sludge that reduces colour concentration. The removal of NH3-N increased from 50.0% to 93% when EC was integrated with clinoptilolite zeolite adsorption. In conclusion, the results show that both processes can potentially remove colour while the integrated process effectively removes NH3-N from landfill leachate. The proposed treatment helps optimise process performance while minimising the operational cost of the treatment. Thus, the proposed integrated EC – zeolite adsorption processes can be an alternative to landfill leachate treatment which aligns with the 12thMalaysia Plan to reduce pollution and carbon emissions to become a carbon neutral nation as early as 2050.

The scope of alum coagulation-flocculation assisted by slaked lime for the treatment of industrial wastewater containing highly concentrated Acid Black 194 dye. Optimization, molecular weight distribution and toxicity analysis

This work evaluated the capacity of the alum coagulation-flocculation (C–F) process, assisted by slaked lime, for the treatment of industrial textile wastewater (ITWW) containing highly concentrated Acid Black 194 dye. By optimizing the operating conditions ([Alum] = 16.09 g/L, [Ca(OH)2] = 5.16 g/L) through experimental design, response surface methodology, and multi-objective optimization analysis, the C–F process removed 95 % of the dye, 63 % of the COD, 60 % of the TOC, and 94 % of the total Cr concentration, with a total operating cost of 5.99 USD/m3. This improved the biodegradability index (from 0.20 to 0.26), the COS parameter (from 0.14 to 2.46), and the toxicity of the effluent (LC50 for Artemia salina increased from 15.16 mg/L to 56.7 mg/L). The calcium hardness and total hardness were also reduced by 40 % and 44 %, respectively. The C–F supernatant was composed mainly of molecules with molecular weights less than and equal to 10 kDa. An LC-MS spectral analysis revealed the presence of four residual aromatic and recalcitrant compounds in the C–F supernatant, indicating that its further treatment is required before it can be safely discharged or recycled for industrial purposes. The alum C–F process, assisted by slaked lime, demonstrated greater performance, surpassing the individual processes in effectiveness and efficiency, and confirming their synergetic effect. The alum process alone (16.09 g/L) achieved a 37 % reduction COD and 91 % color removal, at a total cost of 4.49 USD/m3. The lime process alone (5.16 g/L) achieved a 37 % COD reduction and 64 % color removal, at a total cost of 1.36 USD/m3.

Degradation by photo-Fenton process using Fe-clay as heterogeneous catalyst under sunlight and microwave irradiation

This study presents a newly developed, highly efficient heterogeneous iron-based catalyst (Fe-CY), supported on treated bentonite clay (CY), designed for the degradation of methylene blue (MB) dye. The bentonite clay underwent a two-stage treatment involving physical and chemical processes to produce the designated treated clay (CY), which served as the support material for Fe-CY catalyst preparation using the wet impregnation technique. Subsequently, the performance of the resulting catalyst was assessed in a photo-Fenton reaction aimed at degrading MB dye under both solar and microwave irradiation conditions. To determine the optimal decolorization conditions, several variables, including catalyst dosage, H2O2 quantity, pH, and initial MB concentration in the reaction system, were systematically investigated. Miscellaneous characterization techniques were employed to assess the support, and prepared catalyst. X-ray diffraction (XRD) was used to determine crystallinity, scanning electron microscopy (SEM) to analyze morphological structure, Fourier-transform infrared spectroscopy (FTIR) to identify surface functional groups, energy dispersive X-ray (EDX) analysis for the purpose of elemental analysis, and Brunauer-Emmett-Teller (BET) for analyzing the textural properties. The experimental findings highlight the remarkable effectiveness of the catalyst in degrading methylene blue (MB). Upon exposure to sunlight and microwave irradiation, the catalyst achieved substantial MB color removal rates of 99.5% and 95.5% within 180 and 8 min, respectively. Moreover, the stability of the catalyst was evaluated across three consecutive cycles, revealing a sustained removal efficiency of 83.05%. Finally, a comprehensive investigation into the mechanism behind methylene blue (MB) removal was conducted, revealing insights into the unique catalytic properties of the Fe-clay catalyst.

Water recovery and treatment of spent filter backwash from drinking water using chemical reactor-ultrafiltration process

During routine operations of water treatment plant (WTP), production of spent filter backwash water (SFBW) is inevitable that imposes high operation and maintenance costs. The study investigates treatment and water recovery from SFBW from WTP via combined chemical reactor-ultrafiltration (CR-UF) process. The daily generated SFBW from full-scale treatment plants were treated by the pilot pant of CR-UF process, which is comprised of a primary sedimentation basin, coagulation and flocculation tank immersed UF membrane module. The optimum conditions for CR process were pH 7.5 and FeCl3 dose 20 mg/L, which led to significant removal of turbidity, color, and UV254 that are equal to 97.11 ± 0.10 %, 63.31 ± 1.98 %, and 30.74 ± 0.72 %, respectively. The CR-UF produced permeate with very low turbidity (0.3 ± 0.01 NTU and 93.0 ± 1.1 % removal) has met the water standard of 5 NTU. During the continuous operation of CR-UF process and after three consecutive cycles of UF backwashing, initial flux slightly declined from 8.57 L/m2.h in the 1st cycle to 8.20 L/m2.h in the 3rd cycle, demonstrating the irreversible fouling due to nanoparticle blocking. In four proposed blending of SFBW, the amount of UV254 and TOC did not change significantly (<1 % increase), and additional coagulant was not needed. The hazard index (HI) values for all the population groups were <1, suggesting a minimal adverse health risk regarding the consumption of treated SFBW by the CR-UF process. Overall, the permeate stream of CR-UF process can be reused as a source of raw water for drinking water treatment plant.