Optimum Chemical Oxygen Demand Research Articles

Pilot microbial electrolysis cell closes the hydrogen loop for hydrothermal wet waste conversion to jet fuel

The global shift toward net-zero emissions necessitates resource recovery from wet waste. In this study, we demonstrate the first feasibility of combining pilot-scale microbial electrolytic cells (MECs) with hydrothermal liquefaction (HTL) for simultaneous post-hydrothermal liquefaction wastewater (PHW) treatment and efficient hydrogen (H₂) production to meet biocrude upgrading requirements. Long-term single reactor operation revealed that fixed anode potential enabled rapid startup, and low catholyte pH and high salinity were effective in suppression of cathodic methanogenesis and acetogenesis – resulting in high current density of 16.6 A m−2 and 9.3 A m−2 when feeding synthetic wastewater and PHW respectively. Additionally, the anode biofilm exhibited spatial variations in response to local environmental conditions. Onsite parallel or serial operations of multiple MECs showed good performance using actual PHW with a record-high H2 production rate of 0.5 L LR day−1 for MEC over 10 liters scale, and the optimal chemical oxygen demand (COD)-to-H2 yield reached 0.127 kg-H2 per kg-COD, supporting a self-sufficient, closed-loop upgrade to jet fuel.

The treatment of high concentration wastewater in the natural gas processing industry.

The operation of the Cansolv tail gas treatment device in natural gas plants generates acidic and alkaline wastewater from the venturi unit and amine purification unit (APU), respectively. The APU wastewater is complex in composition and contains hard-to-degrade organic matter, which can adversely impact the normal functioning of the water treatment system. This study assesses the efficacy of three ozone-based advanced oxidation processes (ozone (O3), ozone/hydrogen peroxide (O3/H2O2), and ozone/Fenton (O3/Fenton)) for treating Cansolv wastewater, with chemical oxygen demand (COD) and total organic carbon (TOC) serving as indicators of organic degradation. The findings demonstrate that all three processes effectively eliminate coloration and reducible sulfur, with O3/Fenton exhibiting superior performance in removing organic substances. The treated wastewater has a clarified light-yellow appearance with residual COD levels at 43 mg L-1. Under the optimum Fenton oxidation conditions (initial pH 5, H2O2 dosage 97.8 mmol L-1, FeSO4·7H2O dosage 550 mg L-1), average TOC and COD removal rates reached 50% and 97%, respectively. After a treatment duration of 60 minutes, the wastewater demonstrated an enhanced membrane-specific flux, confirming the effectiveness of the O3/Fenton oxidation process in mitigating membrane fouling while ensuring the stable operation of the wastewater treatment system.

Enhanced removal of nano-oil droplets utilizing polysilicate aluminum ferric (PSAF): Leveraging bridging and non-polar surface advantages.

Hydraulic oil leaks during mechanical maintenance, resulting in flushing wastewater contaminated with dispersed nano-oil droplets. In this study, 75 mg L-1 of polysilicate aluminum ferric (PSAF) was stirred at 350 rpm and the optimal chemical oxygen demand (COD) removal was 71%. The increase of PSAF led to more hydrolysis of Fe, and 1,175 cm-1 hydroxyl bridged with negative oil droplets. At the same molar concentration, PSAF hydrolyzes cationic metals more rapidly than polymeric aluminum chloride (PAC). PSAF forms flocs of smaller complex structures with greater bridging. The Al-O and Si-O peaks occurred at 611 and 1,138 cm-1, indicating the formation of Si-O-Fe and Si-O-Al bonds on the flocs surface. Higher stirring speeds did not change the free energy of the flocs surface γTot, mainly because the decrease in the van der Waals force (γLW) offset the increase of Lewis acid-base force (γAB). Preserving the non-polar surface, in summary, owing to its bridging abilities and affinity for non-polar surfaces, PSAF demonstrates superior efficiency over PAC in capturing and removing oil droplets.

The treatment of petrochemical wastewater via ozone-persulfate coupled catalytic oxidation: mechanism of removal of soluble organic matter.

Petrochemical wastewater contains a variety of organic pollutants. Advanced oxidation processes (AOPs) are used for deep petrochemical wastewater treatment with distinct advantages, including the complete mineralization of organic substances, minimal residual byproducts, and compatibility with biological treatment systems. This work evaluates the effectiveness of three methods, namely, ozone, persulfate, and O3-PMS (ozone-persulfate) processes, which were compared to remove soluble organic matter. The O3-PMS process offered significant advantages in terms of organic matter removal efficiency. This process involves ozone dissolution in an aqueous persulfate solution, producing a more significant amount of hydroxyl radicals in comparison to single AOPs. The production of hydroxyl radicals and the synergistic effect of hydroxyl radicals and persulfate radicals were investigated. In the O3-PMS process, transition metal ions were added to understand the mechanism of the O3-PMS coupled catalytic oxidation system. The results showed that when the ozone concentration was in the range of 5 ~ 25mg/L, the dosage of persulfate was in the range of 0.01 ~ 0.05mol/L, the dosage of metal compounds was in the range of 0:0 ~ 2:1, and the reaction time was in the range of 0 ~ 2h; the optimum chemical oxygen demand (CODCr) and total organic content (TOC) removal effect was achieved under the coupled system with an ozone concentration of 10mg/L, a persulfate dosage of 0.02mol/L, a 1:2 dosage ratio of between Fe2+ and Cu2+ compounds, and a reaction time of 2h. Under optimal reaction conditions, the rates of CODCr and TOC removal reached 70% and 79.3%, respectively. Furthermore, the removal kinetics of the O3-PMS coupled catalytic oxidation system was analyzed to optimize the removal conditions of COD and TOC, and the mechanism regulating the degradation of dissolved organic matter was explored by three-dimensional fluorescence and GC-MS technology. Thus, O3-PMS coupled catalytic oxidation is an effective process for the deep treatment of wastewater. The careful selection of transition metal ions serves as a theoretical foundation for the subsequent preparation of catalysts for the ozone persulfate oxidation system, and this study provides a suitable reference for removing organic matter from petrochemical wastewater.

Improving MFC efficiency in power generation and COD removal by using protic ionic liquid in MWCNT-CS-2-aminothiazole-SO3H nanoparticle-infused sulfonated PES

This study exhibits a novel nanofiller, functionalized multi-walled carbon nanotube (MWCNT)/chitosan (CS) by 2-aminothiazole/SO3H. This synthesized nanofiller was incorporated with a fabricated sulfonated polyethersulfone (SPES) to manufacture a composite proton exchange membrane (PEM), SPES/MWCNT-CS-2-aminothiazole-SO3H. The composite membranes were fabricated by different percentage amounts of nanofiller (0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%). The trait comparison of SPES/MWCNT-CS-2-aminothiazole-SO3H, SPES, and Nafion 117 membrane is performed to investigate their application in the microbial fuel cell (MFC). The fabricated composite membrane SPES/MWCNT-CS-2-aminothiazole-SO3H 0.5 wt% illustrated superior water uptake (WU) of 90.41 %. Moreover, the maximum power density (PD) (66.04 mW.m−2) was produced by SPES/MWCNT-CS-2-aminothiazole-SO3H 0.5 wt%, which demonstrated a considerable increase (approximately 20 times) compared to SPES (3.19 mW.m−2). Furthermore, the power density generated by the Nafion 117 membrane was 15.78 mW.m−2. In addition, the statistics in MFC usage presented that prepared composite membrane combined with MWCNT-CS-2-aminothiazole-SO3H 0.5 wt% had the optimum chemical oxygen demand (COD) removal, and the coulombic efficiency (CE), with 90.46 % and 80.68 %, respectively. Due to the high efficiency and remarkable power generation achieved by the MFC with SPES/MWCNT-CS-2-aminothiazole-SO3H 0.5 wt%, this modified membrane can be considered as a promising cost-effective alternative separator in MFC.

Long-term microbiota and performance monitoring of a highly efficient propylene oxide co-production methyl tert-butyl ether production wastewater treatment plant

A wastewater treatment plant (WWTP) was constructed specifically to treat 543,900 m3 wastewater annually generated by a novel propylene oxide (PO) co-production methyl tert-butyl ether (MTBE) petroleum chemical factory in this study. The WWTP consisted of expanded anaerobic granular sludge beds (EGSBs) and aerobic activate sludge tanks (AASTs), which have been operated for 1340 days. The chemical oxygen demand (COD) and petroleum oils of the WWTP influent were 5140 ± 844 mg/L and 70.08 ± 16.57 mg/L, respectively. The overall removal efficiencies for COD petroleum oils were 94.43% ± 2.36% and 93.46% ± 5.95%, respectively. EGSBs account for 41.48% ± 10.52% of the total COD removal, while AAST contributed to 52.95% ± 10.18%. AAST played a prominent role in the removal of petroleum oils. The optimum COD volume loading rate (VLR) of EGSBs during the operation was 1.83 ± 0.10 kg COD/m3/d, whereas the average COD VLR of AAST was 0.45 ± 0.09 kg COD/m3/d. The composition of dominant microorganisms found in EGSBs and AASTs significantly enhance the performance and efficiency of the WWTP. This study underscores the potential of employing a similar approach for long-term and efficient treatment of industrial complex pollutants, while also highlighting the presence of microbiota with exceptional capability to remove petrochemical contaminants.

In-ground lagoon anaerobic digester in the treatment of palm oil mill effluent (POME): Effects of process parameters and optimisation analysis

Most researchers analyse and optimise the anaerobic performance based on the data generated from pilot plants and laboratory scaled experiments, but not from the industrial scale biogas plant. Therefore, this study aims to evaluate, compare, and optimise the performances of an In-ground Lagoon Anaerobic Digester under mesophilic conditions in four different biogas plants (BGP A, B, C and D) located in Malaysia, for total chemical oxygen demand (COD) removal and total biogas produced. Organic loading rate (OLR), temperature, recirculation ratio (RR) and plant location are found to have significant effects on COD removal and biogas production. Sensitivity analysis shows that BGP A, B, and C show a similar trend of sensitivity, i.e., OLR > Temperature > RR. Conversely, the temperature has the highest sensitivity contributing to the Chemical Oxygen Demand (COD) removal for plant D. Despite having a similar anaerobic digester design for each biogas plant, the optimum operating parameters of OLR, temperature and recirculation ratio vary from plant to plant. BGP B can achieve the highest COD removal (1.21 X 106 kg CODin/month) as well as biogas production rate (4.12 X 105 Nm3/month), with a corresponding methane yield of 0.28 Nm3 CH4/kg CODremoved when the optimal operating parameters for OLR, temperature and RR are configured at 1.60 kg CODin/m3 day, 37.7 °C and 2.08 respectively. It could be concluded that moderate OLR (<1.6), moderate T (<44 °C), and moderate RR (<2.3) are required to achieve optimum COD removal and biogas production for each biogas plant.

Hydrothermal and thermal-acid pretreatments of wheat straw: Methane yield, recalcitrant formation, process inhibition, kinetic modeling

Bio-methanation of agro-residue could fulfill the rising energy demands and curb the environmental pollution. Nevertheless, hydrolysis is the rate limiting step in anaerobic digestion (AD) of agro-waste (wheat straw, WS) due to its recalcitrant lignocellulosic composition. Hydrothermal (100–175 °C, 30–120 min) and thermal-acid (100–175 °C, 0.5–2% H2SO4 v/v) pretreatments of WS were performed to assess the pretreatment effects on WS solubilization, recalcitrant formation, lignocellulosic composition and improvement in methane yield. The 60-min hydrothermal pretreatments had an optimum chemical oxygen demand (COD) solubilization. The hydrothermal pretreatment degraded predominantly the hemicellulose by 53.4%. The furan derivatives, i.e., furfural and 5-hydroxyl-methyl-furfural (5-HMF) were formed during hydrothermal pretreatment of WS at 175 °C. The furfural and 5-HMF were generated at all studied thermal-acid pretreatment conditions owing to hemicellulose solubilization. The anaerobic co-digestion (AcoD) of hydrothermally and thermal-acid pretreated WS was performed with food waste and cow manure in a batch assay. The hydrothermally pretreated WS showed 4–14% higher methane production, while the thermal-acid pretreated WS had 29–44% less methane production than untreated WS. High concentrations of furfural, 5-HMF, total volatile fatty acids (tVFA), and NH4–N affected the methane production in digesters treating thermal-acid pretreated WS. The kinetic analysis of the assays revealed that methane production was affected by furfural, 5-HMF, temperature and acid dosing. Therefore, the calculated values through modified Gompertz and logistic models deviated from the experimental values.

Coagulation and ozonation treatment of biologically treated wastewater from recycled paper pulping industry: effect on the change of organic compounds.

Recycled paper pulping wastewater (RPPW) will cause serious environmental problems due to the high loads of dissolved organic matter (DOM) and toxic components. In the present work, the degradation of DOM in the biologically treated RPPWs (cardboard wastewater (CW) and corrugated container wastewater (CCW)) by a combined coagulation and ozonation process was investigated. The optimal chemical oxygen demand (COD) removal of CW reached 73.64% at aluminum sulfate (Al2(SO4)3) dosage of 800 mg/l, aeration aperture of 10 μm, pH of 9, hydrogen peroxide (H2O2) dosage of 100 mg/l, and reaction time of 70 min. The optimal COD removal of CCW reached 55.76% at a poly-aluminum chloride (PAC) dosage of 700 mg/l, H2O2 dosage of 140 mg/l, and reaction time of 50 min. This study provided some insights into the change of DOM during the combined treatment through the use of UV-Vis spectroscopy and excitation-emission matrix spectroscopy (EEM). PAC and Al2(SO4)3 removed high molecular weight organic such as lignin and lignin-derived compounds to improve the biodegradability of the wastewater. Ozone oxidized high molecular weight organic with complex functional groups to low molecular weight organic with simple functional groups and even mineralization, and this phenomenon resulted in the COD of ozonation effluent significantly reduced. Thus, the results presented in this study support the application of the combined coagulation and ozonation process in treating RPPW.

Treatment of Dairy Wastewater by Electrocoagulation using Iron Filings Electrodes

This study investigated the treatment of dairy wastewater using the electrocoagulation method with iron filings as electrodes. The study dealt with real samples collected from local factory for dairy products in Baghdad. The Response Surface Methodology (RSM) was used to optimize five experimental variables at six levels for each variable, for estimating chemical oxygen demand (COD) removal efficiency. These variables were the distance between electrodes, detention time, dosage of NaCl as electrolyte, initial COD concentration, and current density. RSM was investigated the direct and complex interaction effects between parameters to estimate the optimum values. The respective optimum value was 1 cm for the distance between electrodes, (60 – 120) min for detention time, 250 mg NaCl/L added, C0/6 = 5,775 mg COD/L as initial COD concentration, and 7.884 - 8.077 mA/cm2 as current provided. At the optimum parameter values, the optimum COD removal efficiency was 73.4%. Meanwhile, the study also performed removal efficiency for nitrogen (N) and phosphate (P) due to their effects on the aquatic life and systems. The optimum removal efficiency for phosphorus and nitrogen was 98.0% and 80.3%, respectively. Due to its effects on the environment and to comply with local legislations, treating these wastewaters using eco-friendly processes was highly recommended taking in consideration the economic feasibility, flexibility and easiness to operate. In addition, the study proved that the high surface area for iron filings played a crucial role in removing process.

High biogas evolution of distillery wastewater under potassium toxicity in a three-stage upflow anaerobic sludge blanket

This investigation aimed to enhance the methanogenic activity of distillery wastewater containing high potassium (K) content in a mesophilic three-stage upflow anaerobic sludge blanket (UASB). The three-stage UASB could not function at a chemical oxygen demand (COD) loading rate greater than 3 kg/m3d due to the K toxicity, causing system failure. The K concentration in the distillery wastewater was 9000–10,000 mg/L, close to the severe inhibitory range for anaerobes (> 12,000 mg/L). Hence, the wastewater was diluted to reach moderate K toxicity. Surprisingly, the three-stage UASB could function effectively, providing high optimum and maximum COD loading rates (20 and 40 kg/m3d, respectively). This was because the three-stage UASB was regulated under a slow stepwise increase in the COD loading rate to achieve fully adapted anaerobe communities for each COD loading rate. This then led to the high ability to withstand the moderate inhibition of K via the successive development of sludge granules.

Determination of Coagulant Dosage and Stirring Time in Laboratory Wastewater Pretreatment

The use of chemicals in practical activities or research in the laboratory will certainly produce wastewater. Wastewater generated from the laboratory is classified as hazardous and/or toxic waste. Based on the substances contained in laboratory wastewater in terms of accumulated amount and a long period of time, wastewater will pollute the environment and will have an impact on living things around it if it is directly discharged into water bodies. The composition of laboratory waste is reactive and dangerous because it contains heavy metals Pb, Fe, and Cu as well as high Chemical Oxygen Demand (COD) and Total Suspended Solid (TSS) so it is difficult to decompose in nature. This study aimed to prepare the laboratory wastewater using the coagulation process as pretreatment. Therefore, this research prioritized the reduction of heavy metal levels of Pb, Fe, and Cu and reduced the content of COD and TSS with Alum as a coagulant. The highest degradation percentage of COD and TSS content occurred at the Coagulation Dose of 80 ppm, namely 99.79% and 99.80% respectively. Meanwhile, the highest degradation percentage of heavy metal levels of Pb, Fe, and Cu as well as the optimum COD and TSS content occurred at a stirring time of 60 minutes respectively, which were 49.48%, 58.96%, 94.09%, 99.97%, and 99.40%. It was concluded that the pretreatment of laboratory wastewater using the coagulation process could reduce the levels of Pb, Fe, and Cu metals, and the content of COD and TSS.

A hybrid process for leachate wastewater treatment: Evaporation and reverse osmosis/sequencing batch reactor.

In this study, a hybrid process for leachate wastewater treatment including evaporation and reverse osmosis (RO) membrane or biological treatment systems was suggested. Experiments were performed on a real landfill leachate wastewater. The leachate was subjected to evaporation; as a result, a distillate was obtained containing less organic matter and less substantial amounts of other pollutants, as ammonium salts and total phenols were removed. Tests were carried out at different evaporation temperatures and times. The initial leachate pH was adjusted and optimized. For optimum conditions, each of chemical oxygen demand (COD), total phenol, and ammonium salt concentrations were reduced to 99.99%, 95.00%, and 83.00%, respectively. The distillate of the first stage of the proposed process was then exposed to RO membrane system, as a first study, under different transmembrane pressure of 20, 30, and 40 bar and at different pH values of 7, 8, and 9. As a second suggested treatment system, the distillate was subjected to a biological treatment process for 30 days as a retention time, pH = 6, and room temperature 25°C ± 1°C. At the end of the research study, a comparison was conducted between results obtained with RO membrane separation and biological treatment system as two distinct treatment systems proposed for leachate landfill wastewater treatment. Although both systems were effective for landfill leachate wastewater treatment, however, with the RO membrane separation system, COD removal efficiency reached 99.99%. In the other hand, with biological treatment process, COD elimination was as much as 90.00%. Certainly, evaporation and RO are not novel ways of landfill leachate treatment; however, few studies have attempted to use similar combined system for landfill leachate wastewater treatment and attained effective results of treated water. PRACTITIONER POINTS: A hybrid process of evaporation and RO membrane or biological treatment systems was suggested for leachate wastewater treatment. For optimum conditions, COD, total phenols, and ammonium salt reductions were achieved to 99.99%, 95%, and 83%, respectively, after the first evaporation stage. The distillate of the first stage of the proposed process was then exposed to RO membrane system and biological treatment system. Different transmembrane pressure and different pH values were optimized for RO.

Electrogenic potential of Enterococcus faecalis DWW1 isolated from the anodic biofilm of a dairy wastewater fed dual chambered microbial fuel cell

In this investigation, a novel electrochemically active Gram positive bacterium was isolated from the biofilm of a dual chambered microbial fuel cell (MFC) flooded with dairy wastewater (DWW), and was annotated as Enterococcus faecalis DWW1 following the 16 s rRNA sequencing. The dye-reduction based electron-transfer activity (DREAM) assay was used as a simple criterion for evaluation of electrochemical activity (0.43) in the candidate microbe. The electrochemical activity of the strain DWW1 was characterized using cyclic voltametry (CV). CV studies revealed that the redox compound present in the DWW was exploited by the strain DWW1 for extracellular electron transfer towards anode. Current generation and chemical oxygen demand (COD) removal efficiencies of the strain DWW1 was examined following an optimum COD concentration of 1.440–1.665 kg COD/m3 and anolyte pH of 8 (maximum current density 258 mA/m2; power density 144 mW/m2, 220 Ω; COD removal efficiency 53.5%; coulombic efficiency 10.89%). Such observations revealed the potential of E. faecalis DWW1 towards DWW remediation and energy generation.

Optimisation of operating conditions during coagulation-flocculation process in industrial wastewater treatment using Hylocereus undatus foliage through response surface methodology.

In exploring the application of natural coagulants in industrial wastewater treatment, plant-based coagulants have been gaining more interests due to their potential such as biodegradability and easy availability. Hylocereus undatus foliage as a plant-based coagulant has been proven to be efficient during the coagulation-flocculation process; however, limited research has been reported focusing only on palm oil mill effluent (POME) and latex concentrate wastewater. In addition, no previous study has been carried out to determine the performance evaluation of Hylocereus undatus foliage in treating different types of wastewater incorporating different operating conditions using optimization techniques. Hence, this study employed response surface methodology (RSM) in an attempt to determine the performance evaluation of the coagulant in paint wastewater treatment. Four independent factors such as the pH value, coagulant dosage, rapid mixing speed and temperature were chosen as the operating conditions. Three water parameters such as turbidity, chemical oxygen demand (COD) and suspended solids (SS) were chosen as responses in this study. Results revealed that through central composite design (CCD) via Design Expert software, the optimum conditions were achieved at pH 5, coagulant dosage of 300mg/L, rapid mixing speed of 120rpm and temperature at 30°C. The experimental data was observed to be close to the model predictions with the optimum turbidity, COD and SS removal efficiencies found to be at 62.81%, 59.57% and 57.23%, respectively.

Low cost electrocoagulation process for treatment of contaminated water using aluminium electrodes from recycled cans

Electrocoagulation has been used to successfully treat diverse types of wastewaters. This treatment is carried out when there is an electro-dissolution of soluble anodes to form metal hydroxide flocks within the effluent. In this work an electrocoagulation setup was used to treat water from a contaminated stream. Aluminium anodes produced from recycled cans were used as electrodes. The contact time and voltage during electrocoagulation were varied and the corresponding effects on pH, Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and electrode weight gain/loss were observed. The average TDS of the raw water before Electrocoagulation was 286.7 mg/L. At 10 V, 20 V and 30 V, the average TDS of 246.3 mg/L, 227.3 mg/L and 220.7 mg/L were obtained after 120 min of electrocoagulation. The reduction in TDS signified improved anode dissolution and thus improved water quality. The results show that optimum COD and BOD removal efficiencies of 90.7% and 97.67% were obtained at 10 V.

Flocculation of combined contaminants of dye and heavy metal by nano-chitosan flocculants

In this study, two multifunctional nano-chitosan flocculants (CPAM-NCS1 and CPAM-NCS2) were made through the graft modification of cationic monomer and carboxymethylchitosan (CMCTS) to remove combined contaminants. The effects of various factors (pH, flocculant dosage and hydraulic mixing conditions) on the flocculation performance under single and composite pollution conditions were systematically investigated, the optimal chemical oxygen demand (COD) and the chromaticity removal rates in the dye wastewater were 79.9% and 83.9% at wastewater pH 7, the fast stirring rate 300 rpm, the fast stirring time 8 min, and the dosage of CPAM-NCS1 80 mg/L, respectively. The optimal removal rates of Cu (II) obtained by CPAM-NCS1 and CPAM-NCS2 at were 80.3% and 75.2% at 60 mg/L and the wastewater pH 7, respectively. The optimal removal rates of Cu (II) and disperse orange were 85.3% and 89.4%, respectively, in a composite pollutant system in which Cu (II) and disperse orange coexisted when the pH of the composite system was 9 and the dosage of CPAM -NCS1 was 60 mg/L. This study proved that nanoflocculants made by modifying CMCTS with different structures can demonstrate ideal flocculation removal performance for dye and heavy metal wastewaters.

Sequential three-step process for the treatment of slaughter house wastewater and its optimization using response surface modeling studies

The rapid growth in the world population and fast developing industrialization have resulted in the acceleration of environmental pollution due to inadequate treatment methods accompanied by depletion of freshwater. The current research focused on the batch treatment of slaughter house wastewater (SWW) using the sequential three-step electro-coagulation (EC)–electro-oxidation (EO)–adsorption column (AC) processes and to compare the optimized values with the Omani National Standards for the application in irrigation purpose. The characterization of SWW before and after treatment was carried out by measuring chemical oxygen demand (COD), total organic carbon (TOC), total dissolved solids (TDS), turbidity, ammoniacal nitrogen (NH4–N) and conductivity. The optimization of the treatment processes was performed by response surface methodology (RSM) using central composite design. The maximum response obtained using EC unit was 99% with an operating cost of 2.78 USD/m3. The optimum treatment conditions in EC method were found to be 4.0 pH, electrolysis time of 30 min and electrolyte dosage of 5 g/L, with a current density of 18.11 mA/cm2. The maximum reduction in COD was 97% with an operating cost 0.32 USD/m3. The optimum COD reduction in EO method was 84.5% with an operating cost of 6.87 USD/m3. The optimum process parameters in the EO process were observed at 5.0 pH, 56.22 min electrolysis time with 5 g/L electrolyte dosage and a current density of 5 mA/cm2. The response shows 56.27% reduction in COD with an operating cost of 0.088 USD/m3. The study demonstrates that both EC and EO processes for the reduction of COD have a significant effect on the current density. Using adsorption column (AC) studies, the maximum reduction in COD was 76.8% with negligible operating cost. The optimum pH in the case of AC was 7.5, with an effluent flow rate of 8.63 mL/min, and the responses were found to be 76.067%, which indicates both pH and flow rate have significant effect on the % removal of COD.

Promising Potential of Electro-Coagulation Process for Effective Treatment of Biotreated Palm Oil Mill Effluents

The critical parameters namely initial pH, time and current density largely impact the process efficiency of electrocoagulation (EC). Few works have been done on observing the interaction of these critical parameters and the possible combined effect on the overall pollutant removal efficiency. Therefore, the knowledge of the combined effect of critical parameter interaction would enhance the optimization of EC parameters to attain maximum efficiency with limited resources. Using aluminium electrodes with interelectrode distance of 10 mm on synthetic wastewater, representing biotreated palm oil mill effluent (BPOME), with a set range of initial pH, current density, and time of 3-8, 40-160 mA/cm2 and 15 to 60 minutes, respectively, the effect of the three critical variables was investigated. The optimum Chemical Oxygen Demand (COD) removal of 71.5% was determined at pH 6, current density of 160 mA/cm2 (with current 1.75 A) at EC time of 15 minutes. The experiment was validated with real BPOME, resulting in the removal efficiency of 60.7 % COD, 99.91 % turbidity, 100 % total suspended solids (TSS) and 95.7 % colour. Removal of a large quantity of pollutants in a time span of 15 minutes with optimized parameters in EC is notable for a wastewater treatment alternative that requires no extensive use of chemicals. The interaction of parameters observed in this study indicated a synergistic contribution of initial pH and current density in removing maximum wastewater COD in 15 minutes of EC.

Degradation of distillery spent wash using monopolar parallel and monopolar series electrocoagulation process

In waste treatment and water management issues, electrocoagulation (EC) is the most cost-effective and environmentally friendly option. In the study, EC treatment of distillery spent wash was carried out using new electrodes packed with aluminium foil scraps. These metal scraps were packed in a mesh to function as anode and cathode electrodes. Electrochemical treatment was carried out for 150 minutes, and samples were analysed regularly to determine the colour and chemical oxygen demand (COD). The impact of operating parameters such as pH, applied current, electrolysis time, agitation speed, and electrode distance on colour and COD removal was investigated. The EC processes were carried out in monopolar parallel (MP-P) and monopolar series (MP-S). The MP-S connection measured the potential difference between the amplified pair of electrodes, whereas the output signals in the MP-P connection were formed by several input electrodes, resulting in a high removal rate. The results indicated that the MP-P relationships enhance the COD removal rate by 4.16 to 8.06 %. An optimum chemical oxygen demand degradation is 77.29 % at pH 3, and decolourisation is 76.55 % at pH 8.3. TDS is reduced to a maximum of 58.32 %, while sulfate and chloride are reduced to 64.72 and 20.44 %, respectively.