Color Removal Research Articles

A Comprehensive Approach to Azo Dichlorotriazine Dye Treatment: Assessing the Impact of Physical, Chemical, and Biological Treatment Methods through Statistical Analysis of Experimental Data

This exploration investigates integrated treatment systems combining advanced oxidation processes (Fenton and photo-Fenton) with biological methods for the effective elimination of stubborn organic compounds in simulated textile wastewater composed of azo Dichlorotriazine dye. A comprehensive optimization of key process factors including catalyst dosage, hydrogen peroxide quantity, irradiation duration, etc. was systematically conducted for both Fenton and photo-Fenton processes to realize maximum COD and color removal. Under ideal conditions (0.4 g/L photocatalyst, 1 mL/L H2O2, and 75-Watt UV intensity for 60 min), the photo-Fenton process realized 80% COD elimination and complete decolorization, meeting industrial discharge limits without needing extra biological treatment. Statistical models correlating process parameters to treatment efficiency were developed, giving important design insights. For Fenton, effluent COD exceeded discharge thresholds, so a post-biological treatment using activated sludge was essential to comply with regulations. This integrated Fenton–biological scheme utilizes synergism between chemical and biological processes for enhanced overall treatment. Notable economic benefits were achieved by photo-Fenton over conventional UV-only and UV/H2O2 methods regarding energy consumption and operating costs. Overall, this pioneering work successfully proves integrated advanced oxidation–biological systems as a superior, sustainable alternative to traditional techniques for economically removing obstinate pollutants, such as azo Dichlorotriazine dye, as it is a simulated textile wastewater treatment used to satisfy environmental standards.

Aluminum Waste as Electrode for Home Textile Industry Wastewater Treatment using Batch Electrocoagulation Process: Studies on Operating Parameters

The manufacture of the Sasirangan home textile industry involves coloring and dyeing processes using synthetic dyes in large quantities. These contaminants of dyes and organic materials would cause high color and chemical oxygen demand (COD) contaminants values. This study aims to characterize the wastewater of batik-modified Sasirangan and determine the effect of current density and length of operating time on color removal and reduction of COD in Sasirangan home textile industry wastewater through the batch electrocoagulation process. The method used in this research is an electric current flowing in the same direction to the Sasirangan home textile industry wastewater in a reactor with dimensions of 310 180 240 mm3. The electrode used is aluminum alloy type 1100. The aluminum/aluminum (Al/Al) electrode is used in this electrocoagulation (EC) process, then connected to a direct current (DC) power supply. The experiment was carried out at room temperature using an electrode distance of 2 cm with variations in the time of the electrocoagulation process for 15–120 minutes. The experiment was repeated for variations in pH (4–9) with a current density of 3.5–5.5 mA/cm2. Furthermore, an analysis of the color removal and the decrease in the concentration of COD was carried out. The results showed that the contaminant content in Sasirangan home textile industry wastewater decreased significantly, whereas the optimal conditions for the EC reaction were determined using color and COD removal efficiency parameters. The decrease in color and COD concentrations occurred at a current density of 5.5 mA/cm2 with a pH of 4 for 120 minutes, around 1110 PtCo and 90.4 mg/L of COD, respectively

Study on COD and color removal efficiency in textile dyeing wastewater by iron electro-coagulation technology combined with persulfate

Electrocoagulation (EC) is an attractive method for treating many types of wastewater due to its advantages. The purpose of this study is to investigate the effect of persulfate addition on the efficiency of textile wastewater treatment through the removal percentage of COD and color parameters. Persulfate is proven to significantly enhance the rate and efficiency of pollutant removal in textile wastewater. The removal percentage of COD could reach 91.33 ± 1.23% and 97.99% ± 0.52% was the highest removal percentage of the color parameter at the optimal reaction parameters. The effluent concentration meets the standards according to Vietnam national technical regulation on textile industry wastewater. By using persulfate, the COD and color removal efficiency increased by 17.53 ± 2.69% and 8.81 ± 0.91%, respectively, compared to the single electrocoagulation process. The amount of sludge generated in the system is 0.542 ± 0.0357 kg/m3, significantly reduced compared to the flocculation process of 0.875 ± 0.0295 kg/m3.

Investigation of the performance of the combined moving bed bioreactor-membrane bioreactor (MBBR-MBR) for textile wastewater treatment

The present study focused on the investigation of the performance of a Moving Bed Bioreactor coupled with a Membrane Bioreactor (MBBR-MBR) on a small scale for textile wastewater treatment. The parameters examined in this study included the removal efficiency of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), turbidity, color, and heavy metals (HM). The two reactors were operated consecutively and maintained aerobic conditions. The idea is to reduce the pollutant load significantly through the activity of microorganism attached to the biofilm covered carriers in MBBR and successive membrane filtration. The system demonstrated a favorable outcome even in a smaller hydraulic retention time (HRT) of 1 day, which presents a significant advantage in terms of cost and space saving. The removal effectiveness of COD attained a maximum of 92 %, BOD reached a maximum of 95 %, and the color removal performance obtained a removal efficiency of 87 %. Furthermore, the treatment showed remarkable efficiency in removing up to 100 % of TSS and 96 % of turbidity. Additionally, an evaluation was conducted on the elimination of heavy metals, including Zinc (Zn), Lead (Pb), Chromium (Cr), and Iron (Fe). The efficacy of removing these HMs was found to exceed 85 %. All these favorable outcomes contribute to the improvement of effluent quality, mitigation of contamination hazards, and fouling reduction.

Immobilized enzymatic membrane surfaces for biocatalytic organics removal and fouling resistance

This research reported on the immobilization of environmentally friendly enzymes, such as horseradish peroxidase (HRP) and laccase (L), along with the hydrophilic zwitterionic compound l-DOPA on nano-filtration (NF) membranes. This approach introduced biocatalytic membranes, leveraging combined effects between membranes and enzymes. The aim was to systematically assess the efficacy of the enzymatic modified membrane (HRP-NF) in degrading colors in the wastewater, as well as enhancing the membrane resistance toward organic fouling. The enzymatic immobilized membrane demonstrated 96.3 ± 1.8% to 96.6 ± 1.9% removal of colors, and 65.2 ± 1.3% to 67.2 ± 1.3% removal of TOC. This result was underpinned by the insights obtained from the radical scavenger coumarin, which was employed to trap and confirm the formation of PRs through the reaction of enzymes and H2O2. Furthermore, membranes modified with enzymes exhibited significantly improved antifouling properties. The HRP-NF membrane experienced an 8% decline in flux, while the co-immobilized HRP-L-NF membrane demonstrated as low as 6% flux decline, contributed by the synergistic effect of increased hydrophilicity and biocatalytic effects. These findings confirmed that the immobilized enzymatic surface has added function of degrading contaminants in addition to separation function of nanofiltration membrane. These l-DOPA-immobilized enzymatic membranes offered a promising hybrid biocatalytic membrane to eliminate dyes and mitigate membrane fouling, which can be applied in many industrial and domestic water and wastewater treatment.

Removal of reactive black dye color in textile effluent using Palmyra sprout and Moringa oleifera waste bio char

In this study treatment of the textile wastewater by color removal using adsorbent (Palmyra sprout peel and Moringa oleifera peel) is done. This study collects information to discharge color using adsorbent (Palmyra sprout peel and Moringa oleifera peel) which acts as an effective adsorbent. Both the adsorbent Palmyra sprout peel and Moringa oleifera peel are low-cost adsorbent. Moringa oleifera peel is readily available for use, Palmyra sprout peel has seasonal availability. A series of batch experiment was carried out to determine the optimum dosage for color removal using various adsorbent dosage (4 - 12g/lit), and optimum contact time 120 minutes. The efficiency of the color removal was calculated by subtracting initial concentration and final concentration. The pH was varied from 10 to 2 and the color removal rates was found to be from 25% to 93%. Lower pH conditions have increased color removal rate for textile wastewater. Key Words: adsorption, Palmyra sprout peel, Moringa oleifera peel, Reactive black dye (RB5), and dye removal.

Comprehensive study of Fenton reaction efficiency on textile wastewater treatment from dye solution to real effluent with emphasis on Fukui function analysis

This study investigated the continuous degradation monitoring of three reactive dyes, reactive yellow 176 (RY), reactive Blue 4 (RB) and reactive red 293 (RR), both in separate solutions and in a mixture, along with their corresponding dye bath and industrial dyeing effluent, using Fenton reaction. A kinetic study was conducted to compare the degradation efficiency of the studied solutions. This work provides important yield of dye degradation, where the results showed that RB, RY, and RR had 96.64 %, 92.47 %, and 73.27 % color removal, respectively, within a two-hour reaction time. The pseudo-second-order model fit well to describe the degradation of RR and RY, while the zero-pseudo-order model provided a better fit for RB. The dye mixture exhibited 57 % color removal, whereas the dyeing bath and real effluent showed 41 % and 36 % removal, respectively, over a two-hour reaction time. Moreover, significant reductions in chemical oxygen demand (COD) and biological oxygen demand over 5 days (BOD5) were observed, with the real effluent demonstrating a 73.91 % COD reduction and an 86.66 % reduction in BOD5. The COD and BOD5 reductions for the dye bath were 67.53 % and 95 %, respectively. Additionally, COD and BOD5 reductions of 72.96 % and 96.66 %, respectively, were observed for the dye bath. DFT calculations were employed to elucidate the regioselectivity of radical oxidation of the three reactive dyes by Fenton's reagent, providing insights into global and local reactivity descriptors. Toxicity studies further underscored the efficacy of the Fenton reaction in wastewater treatment. Additionally, UV–visible spectral analysis before and after 12 h of Fenton reaction revealed total discolouration and a reduction in UV and visible peaks across all reactions, indicating comprehensive dye degradation and reduction.

Electrooxidation pretreatment prevents membrane fouling and improve treatment efficiency of a membrane bioreactor treating reject water and condensate generated during sludge dewatering

This study explored electrooxidation pretreatment of reject water and condensate generated using sludge dewatering with goal of improving its treatment using a membrane bioreactor (MBR) and also prevent membrane fouling. Initially the important parameters for electrooxidation process were optimized. The results showed that a total current of 4.03 A/L, current density of 60 mA/cm2, pH 7, and 1500 mg/L of Cl- ion concentration were best in terms of solubilization and removal of fouling-causing substances from wastewater. The colour removal from the wastewater could be as high as 92.4% (7 colour unit (CU) of treated effluent) under optimum operating condition. For biological treatment, a four-tank biological system consisting of consequently placed anoxic and aerobic compartments with final tank containing a MBR was used. When compared with untreated wastewater, the MBR treating EO pretreated wastewater showed significant improvement in terms of membrane fouling measured as transmembrane pressure (TMP). Further improvement in the nitrogen and TOC removal could be achieved by extending the EO treatment duration and subsequent HRT of MBR treatment. The findings from the study clearly demonstrates the potential for integrating a combined electrooxidation and MBR treatment in the conventional wastewater treatment plant for reducing its influent pollutant load.

In-situ anion-exchange construction of Z-scheme Ag3PO4/AgI, derived AgCl/Ag3PO4/AgI and Ag2CO3/Ag3PO4/AgI composites with multiple redox energy bands and charge transfer pathways for efficient absorption and sonocatalytic properties

Z-scheme Ag3PO4/AgI composites were synthesized by facile in-situ anion-exchange method at room temperature (RT). All the catalysts have excellent affinity to dyes and adsorb larger than 70 % of Methyl blue. The fastest adsorption equilibrium of Ag3PO4 (qe: 25.9278 mg/g) with low specific surface area (SSA: 4.6624 m2/g) can be rapidly attained for 6 min. The best color removal efficiency (RE) for Methyl blue over all the composites can rapidly increase to 100 % within 45 min. Meanwhile, the highest RE for RhB over S3 is 98.9 % for 60 min, and corresponding rate constant (k) is 0.07018 min−1. After adding NaCl or Na2CO3 into sonocatalysis, because of the formation of novel ternary AgCl/Ag3PO4/AgI and Ag2CO3/Ag3PO4/AgI during sonocatalytic process, the best REs for RhB over S3 composite increase from 89.8 % (no scavenger) to 98.2 % (1.2 mM NaCl), or to 97.6 % (1.8 mM Na2CO3) for 30 min, respectively, and the REs for Methyl blue over S3 are about 100 % for 10 min. From single Ag3PO4 to binary Ag3PO4/AgI, and to ternary Ag2CO3/Ag3PO4/AgI or AgCl/Ag3PO4/AgI, REs are significantly enhanced. New redox energy bands and charge transfer channels lead to efficiently spatial charge separation and further activation of hole (h+), superoxide anions (·O2−), hydroxyl radicals (·OH). Additionally, the relation among oxygen vacancies (Ov), Zeta potential and RE was discussed in detail. Density functional theory (DFT) calculations were used to make clear charge transfer and sonocatalytic mechanism. The evaluation of used samples, adsorption kinetics and modes, diverse degradation pathways and sonocatalytic mechanisms were also discussed in detail. The work provides a novel in-situ strategy for real-time control of catalytic performance by rapidly forming new phase during catalysis at RT. Furthermore, the strategy obviously facilitates real-time development of rare more than ternary composites for enhanced catalytic performance.

Removal of melanoidin from baker yeast plant wastewater: A comparative study on chemical and biological processes

Dark brown color and large quantities of chemical oxygen demand (COD) are challenging for the successful treatment of molasses-based baker's yeast (BY) wastewater. In this study, the sequential biological and chemical coagulation processes were compared in terms of their ability to remove color and COD from industrial molasses-based BY wastewater. In the sequential chemical-biological processes, using the desired dosages of ferric chloride (FeCl3, 4 g/L) and calcium oxide (CaO, 2 % (w/v)) as coagulating agents, the color and COD removal were 90.6 % and 57 %, respectively. The COD removal of the samples from chemical pre-treated wastewater in an aerated biological reactor (reactor A) was improved to 78 %. In sequential biological-chemical processes with extended aeration (bioreactor A), the COD and color removal were 89.1 % and 93.7 %, respectively. The chemical post-treating of the effluent of the combined anaerobic-aerobic system (reactor C) led to COD and color removal of 80.8 % and 94.65 %, respectively. According to experimental findings, the chemical post-treatment was more efficient than the chemical pre-treatment process. This study offers new insights into the utilization of combined systems for the efficient removal of color and COD from industrial wastewater.

Binary color adsorption by zinc@magnetite nanocomposites: Robust parametric optimization using Taguchi method

AbstractThe goal of the current study was to determine the optimal level (value) of adsorption process variables for the adsorption of color from binary aqueous solution. The impact of key adsorption factors, including adsorbent dose, initial color concentration, and contact time, on the color removal effectiveness of Zinc@magnetite nanocomposites (Zin@Fe3O4(ME) produced from bacterial extracts and Zin@Fe3O4(M) produced from bacterial cell mass), has been examined. Utilizing an L9 orthogonal array (OA), average values and the SN ratio for each variable at three diverse points are calculated. ANOVA has determined the most advantageous optimum conditions for raw and SN data. According to the study, the adsorbent dose is shown to be the most important parameter for color adsorption, while contact duration is determined to be the least important factor based on Pareto chart analysis. The percentage of color removal at optimal values for Zin@Fe3O4(M) and Zin@Fe3O4(ME) nanocomposites, respectively, was found to be 81% and 73%. The optimal parameters were found to be 12.5 mg of adsorbent, 125 mg/L initial dye concentration, and 90 min of contact time at pH 7, room temperature. The confirmatory experiments conducted under optimized conditions revealed a higher percentage of color eliminated than was optimized in each test run of the Taguchi design, proving the credibility of the process variables optimized within the designated experiments.

Integration of sequential electrocoagulation and adsorption for effective removal of colour and total organic carbon in textile effluents and its utilization for seed germination and irrigation.

Textile effluent discharge can negatively impact the environment and living organisms due to its potential toxicity, higher percentages of total organic carbon (TOC) contents, and so on. The study investigates the extraordinary performance of the electrocoagulation process (ECP) combined with powdered activated carbon (PAC) as a highly effective and environmental friendly method of treating textile effluents. This scientific work mainly includes the focus on removing toxic components in textile effluents, such as high concentrations of colour and TOC using synthesized PAC derived from coconut shells coupled with the ECP (ECP-PAC). Initially, PAC was characterized by using XRD, Raman, BET, FTIR, and TGA studies. Subsequently, the pilot-scale ECP-PAC batch reactor was constructed with iron (Fe) as an anode and copper (Cu) as a cathode. The pilot-scale ECP-PAC batch reactor has achieved higher treatment efficiency in a shorter reaction time with low energy consumption compared to a stand-alone ECP. Further, the optimum conditions for effective ECP-PAC have been optimized, such as pH 7.5, applied current density (0-50mA/cm2), reaction time (0-30min), electrode combinations (Fe-Cu) with electrode distances of 5cm apart, and an optimum dose of 5g/L of PAC. Specifically, 98% of the colour and 96% of the TOC contents present in the industrial textile effluent were treated in 15 and 30min, respectively. In quantitative perspectives, the developed batch reactor has sharply decreased TOC (324.1mg/L), IC (1410mg/L) and TC (1019mg/L) to 13.55mg/L (96%), 31.49mg/L (97%), and 48.05mg/L (95%), respectively, in 30min demonstrating its sensitivity and selectivity with the utmost care. Moreover, the physicochemical properties of the treated water were convincingly assessed. That is, it remains suitable for the seed germination of mung bean and chlorophyll content study. Thus, the developed methodology could effectively reduce freshwater consumption in the agricultural sector, increase freshwater availability in water-scarce regions, and facilitate the increase of the recharging capacity of groundwater tables.

Fenton and electro-Fenton treatment for industrial textile wastewater recycling. Comparison of by-products removal, biodegradability, toxicity, and re-dyeing

A comparative study of the results obtained from using Fenton and electro-Fenton processes in textile wastewater treatment is presented. Global indicators, color, COD, TOC, and BOD5 were employed to investigate the treatments. Examination of the representative by-products gave new insights into Fenton. Even though the color removal was higher for classical Fenton (almost 100% color removal) than for electro-Fenton, the overall purification effect was not directly advantageous for Fenton. We found that electro-Fenton removed COD and TOC more efficiently. The biodegradability BI (BOD5/COD) parameter was investigated, where the textile wastewater was hardly biodegradable (BI was 0.12 ± 0.007). BI of Fenton was also low (0.044 ± 0.006). Electro-Fenton yielded a considerably more promising result, where BI was 0.83 ± 0.15, and proved more bio-friendly than classical Fenton. Additionally, electro-Fenton was more efficient in by-product removal, especially the naphthalic component, with 90% removal (while Fenton removed 50%). The by-products influenced the after-treatment toxicity assessment of V. fischeri. The EC50 values were below 2% and even lower for electro-Fenton. The results of the color matching parameters (DECMC) of re-dyeing were unacceptable using after-Fenton water at 8.66. DECMC results were between 1.01 and 2.71 after electro-Fenton treatment and had a recycling perspective.

Fe recovery from drinking water treatment sludge for reuse in tannery wastewater treatment: Machine learning and statistical modelling

This work experimentally and numerically studied the reusability of Fe recovered from water treatment sludge as a coagulant and compared its performance with a commercial coagulant in tannery wastewater treatment. The performance of the recycled and commercial coagulants in total suspended solid (TSS), chemical oxygen demand (COD), color, chromium (Cr3+) and turbidity removal was compared with considering pH, coagulant type and dose as independent variables. Additionally, the process was modelled by two statistical and machine learning procedures, i.e., response surface methodology (RSM) and artificial neural network (ANN). For RSM model, a 32 run experimental matrix was designed by factorial design, while ANN model was developed by a dataset extracted from the publications inclusive of the 32 experiments. The results showed Fe recovery rate of 181 mg/g dry sludge. The maximum TSS, COD, color, Cr3+ and turbidity removal by recovered and commercial coagulants were (85 %, 40 %, 42 %, 68 %, and 88 %) and (70 %, 35 %, 49 %, 64 % and 88 %) respectively. ANN COD removal model showed a good prediction in all training, validation and testing phases with R 0.891, 0.963 and 0.917 respectively. While the R for TSS, COD, color, Cr3+ and turbidity statistical models were 0.962, 0.866, 0.960, 0.962 and 0.973 respectively.

Application of response surface methodology for optimization of removal sunset yellow from aqueous by Granular Ferric Hydroxide (GFH)

Color is the first pollutant that is detected in wastewater and can be discharged into the wastewater through various industries. Sunset yellow is an azo dye that is used in the food, health and pharmaceutical industries. Due to its low price and good quality, this color is used in industries more than natural colorants. The aim of this study was to investigate the effect of granular ferric hydroxide (GFH) on the removal of sunset yellow color from aqueous solution using the response surface methodology (RSM). In this study, GFH was employed to remove sunset yellow dye from the aqueous solution. Due to saving time, cost and getting to the optimum conditions, the effect of important factors on adsorption was optimized by the RSM. The morphology of the adsorbent was determined by scanning electron microscopy. The results revealed that optimum conditions for sunset yellow removal by GFH with design experiment were dye concentration= 24 mg/L, GFH dose= 2.4 g/L, reaction time= 25 min. In addition, based on the results, the best-fitted model for this study was the quadratic model (R2 =0.966, R2adj=0.79 and R2pred=0.936). According to the obtained results, GFH was successful in sunset yellow removal. Therefore, it is suggested to use this process to remove sunset yellow from aqueous solutions.

Optimization and PID Control of pH and Temperature in an Electrocoagulation Process

In this work, effects of temperature and pH in batch treatment of pulp and paper mill wastewater using electrocoagulation has been investigated. Conductivity, temperature, and pH are selected as controlled variables; supporting electrolyte, cooling water, acid and base flow rates are selected as manipulated variables, respectively. Real time experimental multi input-multi output (MIMO) control of conductivity, temperature, and pH under constant current conditions are achieved using MIMO Proportional Integral Derivative (PID) control algorithms coded in MATLAB™. A central composite design (CCD) has been applied to the system under controlled conditions and optimum pH and temperature values are obtained using response surface methodology (RSM). Both controlled and uncontrolled experiments are performed using optimum values and results are compared in terms of removal efficiencies of pollutants. Results show that 34.47% chemical oxygen demand (COD), 98.06% total suspended solids (TSS), 99.80% turbidity, 99.93% color, and 13.40% SO42- removal is achieved in 45 minutes of process operation under controlled conditions and COD, TSS, turbidity, color and SO42- removal are increased by 10.92, 2.97, 4.06, 2.89, 3.17 respectively in comparison with uncontrolled operation. The highest removal percentages are obtained under controlled operating conditions as 98.5% and 98.3% for turbidity and color, respectively, for 10 minutes operation. It is concluded that optimum process operating conditions for removal of turbidity and color of pulp and paper mill wastewater is obtained under constant 6.45 pH, 23.24 °C temperature, 1.78 mS/cm conductivity, and power consumption is reduced by 25.3% under controlled conditions.

Modification of Agro-wastes Reinforced onto the PET Fabric for Decolorisation of Palm Oil Mill Effluent

The abundance of agricultural wastes from various industrialized processes has become one of the significant contributors to water pollution, particularly in the color of effluents from industrial-based palm oil mills. Inventively, this research focused on three different agro-wastes: pineapple leaves (PL), rice straw (RS), and empty fruit bunch (EFB) reinforced onto PET fabric composite and its decolorization performances by using palm oil mill final effluent discharged (POME-FED). The calcinated agro wastes/polyvinylidene fluoride (PVDF) reinforced onto the polyethylene terephthalate (PET) fabrics were prepared by using the dip-coating technique and characterized via Scanning Electron Microscopy (SEM-EDS), spectroscopy (FTIR-ATR), turbidity and color of POME-FED. It was found that the calcinated PL/PVDF/Fabric displayed the best performance in the turbidity and decolorization by 12.02 NTU, 760 ADMI, and ~60% color removal efficiency as compared with raw POME-FED (~1800 ADMI). Nevertheless, the decolorization efficiencies of RS/PVDF/Fabric and EFB/PVDF/Fabric had increased by ~37 % and ~49 %, respectively. It shows that the formation of a reinforcing layer on the PET fabric surface has improved the transparency of POME-FED. The SEM micrographs and the change of peaks at regions 1650 cm-1, 1450 cm-1, 1210 cm-1, and 990 cm-1 in composites' spectroscopies demonstrate the different patterns of these calcinated samples are various patterns that impart the strength of the composite fabric surface functionality and hydrophobicity. The reduction of the color value of effluent showed the hydrophobicity of the integrated palm oil waste coated with PET, which enables to trap of the particles in the effluent, thus this composite has potential use in the filtration of water treatment.

The Study of Semi-Continuous Chemical Physical Treatment System for Pollutant Removal in Palm Oil Mill Effluent

Effluent from palm oil mill processing is a major concern due its properties and characteristics that highly contributed to water pollution. This study reported on POME treatment by a semi-continuous treatment system consisting of coagulation, sedimentation and filtration processes in the presence of a by-product coagulant (copperas combined with lime). The treatment was conducted for different types of filter medias (FMs): a) FM 1: sand+activated carbon and b) FM 2: sand+ceramic ring) and various retention times (RT) from 1/2 to 2 h. The treatment resulted in different removal efficiencies of turbidity, colour, chemical oxygen demand (COD) and total suspended solids (TSS) for secondary and tertiary POME samples. With semi-continuous treatment, the pollutants in the secondary POME sample decreased, resulting in the removal efficiency of 57.34% for turbidity, 95.16% for colour, 82.08% for COD and 83.23% for TSS. Meanwhile, the results of the tertiary sample were 54.81%, 81.08%, 78.05% and 68.51% for turbidity, colour, COD and TSS removal respectively. The statistical analysis of ANOVA (p-value<0.05) indicated that the data was statistically significant with the FM 1 as a media filter. As a result, a semi-continous chemical-physical treatment system may provide information in efficient POME treatment.

A Fenton-based approach at neutral and un-conditioned pH for recalcitrant COD removal in tannery wastewater: Experimental test and sludge characterization

The combination of raw animal skin manufacturing processes involves the use of large amounts of chemicals, resulting in the generation of complex and highly polluted tannery wastewater. In this context, the high concentration of chloride in tannery wastewater represents a crucial bottleneck. Indeed, sodium chloride, commonly used in tannery industry to prevent skin rot, increases the concentration of chlorides up to 50 %. At the same time, most of the advanced oxidation processes usually employed in tannery wastewater treatment to remove recalcitrant COD involve the use of conditioning agents, thus increasing the overall concentration of chlorides in the treated effluent. The aim of this study was to evaluate the electrochemical peroxidation process (ECP) efficiency in the treatment of tannery wastewater without changing pH, to improve Fenton technology by avoiding the use of chemicals. The influence of different electric currents on COD and color removal was investigated. The characterization of the produced sludge was conducted through FTIR, SEM and XRD analysis, exploring the morphology and composition of precipitate, depending on the applied current. Although an electrical current of 750 mA yields the highest COD and color removal efficiency (69.7 % and 97.8 %, respectively), 500 mA can be considered the best compromise because of energy consumptions. Iron oxides and hydroxides were generated during the ECP process, playing the role of coagulants through the absorption of organic and inorganic contaminants. The consumption of energy increased as a function of time and applied current; however, cost analysis showed that the electrodes contributed the most to the total cost of the process. In authors' knowledge, the application of ECP process as a tertiary treatment for the removal of recalcitrant COD in tannery wastewater represents a novelty in the literature and the results obtained can be considered as the basis for scaling up the process in future research.

Perspectives on sustainable process control optimization through reusability of non-regenerated Fenton sludge in landfill leachate treatment

The production of iron-rich waste (Fenton sludge) and the high chemical dosage required in the Fenton-based advanced oxidation process (AOP) harm the environment, making disposal challenges and the technique unsustainable. Thus, finding adequate Fenton sludge (FS) reuse alternatives is critical to addressing the Fenton process's drawbacks in addition to environmental protection. This study signifies that FS could be employed satisfactorily without requiring costly regeneration operations or chemical dosages, such as landfill leachate, during wastewater treatment. In this study, two sets of experiments were carried out utilizing the most often used optimization tools: design of experiments (DOE) (central composite design (CCD)/response surface methodology (RSM). Under optimized conditions, reasonably high chemical oxygen demand (COD) removal of 62 %, total suspended solids (TSS) removal of >95 %, and colour removal of >80 % was obtained after 48 min of reaction time with 84 mL/L sludge reused at pH 3.6. The method's key influencing factors were sludge volume, pH, and reaction time. Furthermore, reused FS exhibited lower toxicity and total volatile solids, indicating that sludge reuse is superior to direct disposal. According to the techno-economic analysis, using non-regenerated sludge as proposed reduces toxic iron-based waste and total wastewater treatment costs.