Maximum Chemical Oxygen Demand Removal Research Articles

Enhanced bioenergy production through dual-chamber microbial fuel cells: Utilizing citric acid factory wastewater and grape waste as substrates

IntroductionMicrobial fuel cell (MFC) is a variant of the bio-electro-chemical system that uses microorganisms as biocatalysts to generate bioenergy by oxidizing organic matter. Due to its two-prong feature of simultaneously treating wastewater and generating electricity, it has drawn extensive interest by scientific communities around the world. However, the pollution purifying capacity and power production of MFC at the laboratory scale have tended to remain steady, and there have been no reports of a performance breakthrough. Problem statementThis research was conducted to produce electricity and evaluate the efficiency of chemical oxygen demand (COD) removal from wastewater containing Citric Acid using a two-chamber microbial fuel cell without an intermediary. MethodologyIn this research, citric acid factory wastewater was used as the substrate, graphite as the electrode, Nafion membrane for proton transfer from anode to cathode, and grape waste as a carbon source. These Experiments were performed at room temperature and neutral pH. Also, the effect of three independent variables mixed liquor suspended solid (MLSS), Carbon: Nitrogen: Phosphorus stoichiometric ratio (COD:TKN:P), and grape waste on electricity production and wastewater treatment was investigated. Then, the optimal values of each variable were determined under favorable conditions for electricity generation and COD reduction. ResultsThe MFC was conducted at the optimal values of MLSS 1400 mg/L, the stoichiometric ratio of COD:TKN:P 140:10:1, and the grape waste dose of 1.4 g/L. At these conditions, the obtained maximum power density and current density were 18228.10 mW/m2 and 244.44 mA/m2, respectively. The maximum COD removal was 72% achieved in the values of MLSS 1400 mg/L, the stoichiometric ratio of COD:TKN:P equal to 260:10:1, and 1.4 g/L of grape waste. The maximum open circuit voltage was also recorded as 678 mV, obtained at MLSS 3000 mg/L, the stoichiometric ratio of COD:TKN:P equal to 200:10:1, and for a grape waste dose of 2 g/L. ConclusionThe results of this research showed that the use of grape waste to supply glucose to microorganisms in the MFC system has a significant effect on increasing energy production and COD removal, and it is recommended to conduct additional research in the future to improve the efficiency. However, scalability and practical application potential of these integrated technologies are the challenges towards their real-world applications in small scale trials.

Decolorization of anthraquinone dye (Reactive Blue 4) in the microbial fuel cell by Baker’s yeast: process optimization

The release of anthraquinone dyes in aquatic sources has a huge impact on the environment because of their turbidity, toxicity, mutagenicity, and carcinogenicity effects. Microbial Fuel Cell (MFC) is a hopeful technology for the decolorization of dyes. The goal of the present study is the decolorization of Reactive Blue 4 (RB4) as an anthraquinone dye from an aqueous solution by Baker’s yeast in MFC. The selection of three parameters (dye concentration, glucose concentration, and airflow rate) and optimization of dye decolorization and chemical oxygen demand (COD) removal are performed using response surface methodology (RSM). The results demonstrated that the interaction between parameters does not affect the dye decolorization efficiency, whereas the interaction between dye concentration and glucose concentration was found to be significant for COD removal. Accordingly, the optimum conditions for maximum dye decolorization and COD removal were obtained at a dye concentration of 50 mgL−1, a glucose concentration of 1 gL−1, and an airflow rate of 10 mLmin−1.

Optimization of electrocoagulation process parameters for the treatment of oil industry drill site wastewater.

The effluent from the oil drilling site is a complex mixture of hazardous chemicals that causes environmental impacts on its disposal. The treatment of oil drill-site wastewater has not been explored much, and understanding its characteristics and optimizing the treatment process are required. In the present study, we have optimized the electrocoagulation process with aluminum electrodes for drill-site wastewater treatment. A multi-level factorial center composite design using response surface methodology is applied to optimize the effect of current density (CD), pH, and inter-electrode distance (IED) on chemical oxygen demand (COD) removal. The increasing current density shows a significant increase in COD removal, and a similar trend was observed with a decreased pH. It was found that with current density and inter-electrode distance, the maximum COD removal achieved was 70% at the CD of 19.04mAcm-2 and IED 2.6cm. By varying pH and current density, the COD removal reached up to 90% at pH 6 and CD 19.04mAcm-2. The study shows that the current density is the dominant factor for the process's energy consumption and operating cost, followed by pH. This study's findings could be effectively used to develop large-scale treatment processes through electrocoagulation.

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

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

Oczyszczanie i waloryzacja ścieków z wytłoczyn z oliwek

Wastewater generated during the production of pomace olive oil is complex and highly variable due to different cultivation and processing characteristics. It has a high toxic organic load, low pH, and high chemical and biological demands. To reduce the concentration of chemical oxygen demand (COD) and total phenolic compounds (TPh) in pomace olive oil wastewater, several treatment processes have been studied. These include: (i) coagulation/flocculation, (ii) electrocoagulation, (iii) peroxy-electrocoagulation, (iv) electrochemical peroxidation, (v) Fenton, (vi) electro-Fenton, (vii) photo-Fenton, and (viii) adsorption. Coagulation/flocculation and electrocoagulation resulted in a maximum COD removal of 16%, while techniques involving the addition of hydrogen peroxide (iii-vii) had an average of 78% TPh removal but only 20% COD removal. Adsorption resulted in a maximum of 29% COD and 75% TPh removal. None of the tested techniques were able to remove more than 50% of COD, indicating the difficulty of removing organic matter in this effluent. However, advanced oxidation techniques were effective in degrading phenolic compounds, although they required relatively high dosages of oxidant.

Synergistic effects of Spirulina platensis cultivation in textile wastewater towards nutrient removal and seed germination study

Recent escalating concerns surrounding textile wastewater pollution and the urgent need for sustainable treatment solutions to mitigate its environmental impact. This study investigates the multifaceted effects of Spirulina platensis (SP) cultivation in textile wastewater from two different sources (TWW1 and TWW2), focusing on growth kinetics, Chemical Oxygen Demand (COD), and nutrient removal percentage, and seed germination enhancement. Results showed that SP exhibited comparable growth performance in TWW1 and TWW2 to the control, indicating its potential for sustainable wastewater treatment. Moreover, maximum COD removal percentages were achieved, reaching 62.59 ± 1.88 % for TWW1 and 46.68 ± 1.40 % for TWW2 on day 5. The COD removal process aligns best with the first-order kinetic model. Nutrient removal rates showed decreasing trends over time, with maximum phosphate removal percentages of 36.42 ± 0.73 % for TWW1 and 62.18 ± 1.24 % for TWW2, and maximum ammonia removal percentages of 59.34 ± 1.18 % for TWW1 and 69.31 ± 1.39 % for TWW2. FTIR analysis confirmed pollutant removal-induced changes in algal biomass functional groups. Seed germination studies indicated enhanced shoot and root development of vigna radiatas using treated TWW1 and TWW2 compared to the control, suggesting potential applications for irrigation. An increase in the lipid & carbohydrate content post-treatment was observed and it would be suitable for biofuel production. This comprehensive assessment demonstrates the synergistic benefits of phycoremediation in simultaneously removing pollutants, promoting plant growth, and enhancing wastewater treatment efficiency, underscoring its potential for sustainable water management practices.

Once through continuous mode electrocoagulation for tannery wastewater remediation: Process optimization and performance evaluation

The treatment of wastewater from tannery industries poses significant challenges due to high levels of tannic acid and chemical oxygen demand (COD), along with low biodegradability. To address this issue, we conducted a study focusing on the use of Electrocoagulation (EC) as a treatment process for synthetic tannery wastewater. Iron (Fe) electrodes have been used as anode and cathode as well. The electrodes size (7 cm × 7 cm) has been used in this process. The investigation of removal efficiencies entailed the assessment of total organic carbon (TOC) and chemical oxygen demand (COD) as indicators of organic contaminant levels within the wastewater. The influence of current density, pH, flowrate, and time on the treatment was measured. At a current density of 51 A/m2 with 83.54 % of COD removal and 27 % of TOC removal were observed. The maximum COD removal was found at pH 4.93, flowrate 5 ml/min, current 0.953 A and time 115 min. The current investigation demonstrated the efficacy of the electrocoagulation process in reducing both total organic carbon (TOC) and chemical oxygen demand (COD) levels in synthetic tannery wastewater.

Mechanistic insights of PO43− functionalized carbon nitride homojunction hydrogels in photocatalytic-self-Fenton-peroxymonosulfate system for tetracycline degradation

In this study, metal-free PO43− enriched g-C3N4/g-C3N4 (PGCN) homojunction alginate 3D beads were developed for in-situ H2O2 production under visible light. Later, the photocatalytic-self-Fenton system was integrated with peroxymonosulfate for tetracycline degradation. Initially, the PO43− enriched g-C3N4 (PCN) and a homojunction composed of PCN and g-C3N4 (GCN) were prepared via the wet-impregnation method. Later, PGCN homojunction was formulated into 3D alginate beads through the blend-crosslinking method. The comprehensive characterization of the homojunction beads affirmed the closer contact between the semiconductors, alteration of the bandgap, faster channelization of electron-hole pairs, and improved separation of charge carriers that attributed to higher catalytic efficacy. The PGCN beads exhibited a maximum H2O2 production of 535 ± 12 µM under visible light irradiation for 60 min. The homojunction hydrogels displayed 99 ± 0.25 % tetracycline degradation in 20 min in the photocatalytic-self-Fenton-PMS system. The experimental studies also claimed a maximum chemical oxygen demand removal of 81 ± 3.6 % in 20 min with maximum reusability of beads up to 20 cycles. The Z-scheme electron migration mechanism is proposed based on the results aided by scavenger and electron spin resonance analysis. Overall, the as-synthesized alginate-supported homojunction-based photocatalytic-self-Fenton-peroxymonosulfate system is highly versatile and reusable for energy and environmental remediation.

Adsorptive removal of recalcitrant organic compounds of compost leachate by epichlorohydrin cross‐linked cyclodextrin copolymer

AbstractHazardous materials in compost leachate pose a threat to the environment, and its treatment has become a concern in recent years. The adsorption process is a highly effective method that is used for treating these contaminants. This research pioneered the application of cyclodextrin‐epichlorohydrin (ECP) copolymer for chemical oxygen demand (COD) removal in compost leachate treatment. It offers a practical and effective approach to addressing environmental concerns associated with COD, with an extremely high adsorption capacity of 11,246 mg/g. Fourier transform infrared (FTIR), x‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x‐ray (EDX) analyses were performed to identify the synthesized ECP. The effects of different parameters on the adsorption process were systematically investigated. Organic compounds removal was also evaluated using response surface methodology (RSM) in relation to process parameters. The maximum removal of COD was achieved in acidic solutions with an agitation speed of 160 rpm and adsorbent dosage of 3 g/L at 60 min. The corresponding maximum removal percentage achieved under the optimum conditions was about 70%. The adsorption process followed pseudo−second order kinetics and Freundlich isotherms models. The adsorption behaviour of ECP was investigated in ionic environment and it was efficiently regenerated for three adsorption–desorption cycles. The ECP showed high adsorption capacity and was found to be cost‐effective for COD removal. It was found to be a sustainable waste management strategy.

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.

Sub-pilot scale sequential microalgal consortium-based cultivation for treatment of municipal wastewater and biomass production

Municipal wastewater (MWW) was treated by a sequential pilot microalgal cultivation process. The cultivation was performed inside a specifically designed low-cost photobioreactor (PBR) system. A microalgal consortium 2:1 was developed using Tetraselmis indica (TS) and Picochlorum sp. (PC) in the first stage and PC:TS (2:1) in the second stage and the nutrient removal efficiency and biomass production and biomolecules production was evaluated and also compared with monoculture in a two-stage sequential cultivation system. This study also investigated the effect of seasonal variations on microalgae growth and MWW treatment. The results showed that mixed microalgal consortium (TS:PC) had higher nutrient removal efficiency, with chemical oxygen demand (COD), total phosphate (TP), and total nitrate (TN) removal efficiencies of 78.50, 84.49, and 84.20%, respectively, and produced a biomass of 2.50 g/L with lipid content of 37.36% in the first stage of cultivation under indoor conditions. In the second stage of indoor cultivation, the PC:TS consortium demonstrated maximum COD, TP, and TN removal efficiencies of 92.49, 94.24, and 94.16%, respectively. It also produced a biomass of 2.65 g/L with a lipid content of 40.67%. Among all the seasonal variations, mass flow analysis indicated that the combination of mixed consortium-based two-stage sequential process during the winter season favored maximum nutrient removal efficiency of TN i.e. 88.54% (84.12 mg/L) and TP i.e., 90.18% (43.29 mg/L), respectively. It also enhanced total biomass production of 49.10 g in 20-L medium, which includes lipid yield ∼15.68 g compared to monoculture i.e., 82.06% (78.70 mg/L) and 82.87% (40.26 mg/L) removal of TN and TP, respectively, and produced biomass 43.60 g with 11.90 g of lipids.

EFFICIENCY OF AN UPFLOW ANAEROBIC FILTER FOR POULTRY EFFLUENT TREATMENT

Poultry slaughterhouses discharge large quantities of effluents that can be treated biologically. The objective of this study was to evaluate the chemical oxygen demand (COD) removal efficiency of an upflow anaerobic filter (UAF) with effluents from a poultry slaughterhouse, using volcanic stone (tezontle) as a support medium. Effluent characterization was carried out in accordance with Mexican official standards and standard methods. The support medium was inoculated with activated sludge from an urban wastewater treatment plant. The filter was operated in continuous flow with applied volumetric loads (AVL) of 1, 1.5, 2, 2.5, and 3 kg COD m-3 d-1 and hydraulic retention times (HRT) of 5.8, 3.8, 2.9, 2.3, and 1.9 days. An analysis of variance (ANOVA) was performed, and significant differences were determined for each AVL using the Krustall-Wallis method. The results obtained in the gradually applied AVL were 26.1, 53.2, 40.1, 17, and 49.7 % COD removal. However, in the AVL of 2 and 2.5 kg COD m-3 d-1, there was a decrease in the removal, which is attributed to the destabilization of the system due to the increase in loads. The maximum methane production was 125 mL at an AVL of 3 kg COD m-3 d-1, with a methane yield (YCH4) of 0.082 LCH4 g-1 COD-1rem. With no increase in methane production at each AVL, the theoretical yield of 0.328 LCH4 g-1 COD-1rem. was not met. The upflow anaerobic filter demonstrated its efficiency with a poultry effluent, with maximum COD removal greater than 50 %; however, more acclimatization time is required for the formation of biofilm in the support medium, a pretreatment that removes the high organic load and allows for gradual biogas production.

Influence of pH on the anaerobic fluidised bed reactor performance for palm oil mill effluent treatment

The effect of pH on the performance of a pilot-scale anaerobic fluidised bed reactor (AnFBR) was studied using palm oil mill effluent (POME) as the substrate. The performance of the 2000-litre reactor at different operating conditions, such as organic loading rates and retention times was studied. This acidic agro-industrial wastewater (pH 4.0–5.0) was neutralised by adding slacked lime. It was observed that, within 12 hr of hydraulic retention time (HRT), the AnFBR removes as high as 85% of the substrate chemical oxygen demand (COD) at a loading rate of 4 kg/m3 day. High pre-treatment cost is needed to neutralise the bulk volume of wastewater that was generated from the palm oil industries. Thus, an attempt was made to study the performance of the AnFBR under pH shock load. The influent pH was increased to 9.2 and then dropped around 5.0 to intensify the effect of the pH shock load. At shock load, the reactor performance for COD removal dropped by about 25% lower than the optimum condition. The maximum and minimum COD removal rates during the short period of continuous shock load were 60% and 56.5%, respectively. The average effluent pH remained steady at around 6.1. From the analysis, it was revealed that the anaerobic fluidised bed had the buffering ability and was capable of treating POME with moderate removal efficiency at an influent pH of 5.0.

Investigation of Treatability of Automotive Industry Wastewaters by Coagulation-Flocculation, Fenton and UV/H2O2

In the automotive industry, painting operations have emerged as a major source of environmental concerns. In this study, the treatability of wastewater obtained from the automotive industry painting process was investigated by using coagulation-flocculation, ultraviolet/hydrogen peroxide (UV/H2O2), and Fenton processes. The effects of pH, coagulant, and anionic polymer doses were examined for three different coagulants in the coagulation-flocculation process. Optimal conditions were determined based on chemical oxygen demand (COD) and turbidity removal efficiency. As a result of the study, the optimum conditions for the coagulant identified as ferric chloride, which achieved the highest COD removal of 49.6% and turbidity removal of 74.4%, were determined as pH 8, coagulant dose of 400 mg L-1, and anionic polymer dose of 1 mg L-1. In the second stage of the study, Fenton and UV/H2O2 processes were applied to the effluent of the coagulation-flocculation process to increase the removal efficiency. When the results were evaluated, it was observed that the maximum COD removal efficiency of 63.4% was attained under the conditions of pH 3 and 400 mg L-1 H2O2 concentration applied in the UV/H2O2 process. However, in the Fenton process, a maximum COD removal efficiency of only 51% was achieved. From this study, it can be concluded that the UV/ H2O2 process applied after coagulation-flocculation increases the removal efficiency and can be an alternative and effective treatment process for wastewater from the automotive painting process.

Assessing the effectiveness of electrocoagulation, ozonation and Fenton's oxidation for the treatment of phenalkamine condensate: A comparative study

This study aims to investigate the feasibility of three Advanced Oxidation Processes (AOPs), Electrocoagulation (EC), ozonation and Fenton's oxidation for the treatment of real phenalkamine condensate. Three methods were compared based on COD removal efficiency. Phenalkamines are the Mannich reaction product of cardanol, formaldehyde, and amines. These are widely used in coatings for marine and offshore constructions and as curing agents in industrial adhesives. Cardanol is a derivative obtained by thermal treatment of cashew nut shell liquid (CNSL). The effluent from the cashew nut industry consists of phenolic compounds of high persistence, and they are potentially carcinogenic and mutagenic. The phenalkamine condensate has high pH, high chemical oxygen demand (COD). Fenton oxidation showed the highest COD removal efficiency, with maximum efficiency of 80 % and 94 % achieved after the first stage and five stage Fenton's oxidation respectively at optimized operating conditions. In comparison, EC process and ozonation resulted maximum COD removal efficiency of 54.26 % and 30.64 % respectively at optimum reaction conditions. This study revealed that Fenton's oxidation is the most effective method for the treatment of phenalkamine condensate.

Response surface methodology optimization of the effect of pH, contact time, and microbial concentration on chemical oxygen removal potential of vegetable oil industrial effluents.

The vegetable oil refinery industry generates highly polluted effluents during oil production, necessitating proper treatment before discharge to prevent environmental hazards. Treating such wastewater has become a major environmental concern in developing countries. Chemical oxygen demand (COD) is a key parameter in assessing the wastewater's organic pollutant load. High COD levels can lead to reduced dissolved oxygen in water bodies, negatively affecting aquatic life. Various technologies have been employed to treat oily wastewater, but microbial degradation has gained attention due to its potential to remove organic pollutants efficiently. This study aims to optimize the biodegradation treatment process for vegetable oil industrial effluent using response surface methodology (RSM). The wastewater's physicochemical properties were characterized to achieve this, and COD removal was analyzed. Furthermore, RSM was used to investigate the combined effects of pH, contact duration, and microbial concentration on COD removal efficiency. The result showed that the microbial strain used recorded a maximum COD removal of 92%. Furthermore, a quadratic model was developed to predict COD removal based on the experimental variables. From the analysis of variance (ANOVA) analysis, the model was found to be significant at p < 0.0004 and accurately predicted COD removal rates within the experimental region, with an R2 value of 90.99% and adjusted R2 value of 82.89%. Contour plots and statistical analysis revealed the importance of contact duration and microbial concentration on COD removal. PRACTITIONER POINTS: Response surface methodology (RSM) optimization achieved a significant chemical oxygen demand (COD) removal efficiency of 92% in vegetable oil industrial effluents. The study's success in optimizing COD removal using RSM highlights the potential for efficient and environmentally friendly wastewater treatment. Practitioners can benefit from the identified factors (pH, contact time, and microbial concentration) to enhance the operation of treatment systems. The developed predictive model offers a practical tool for plant operators and engineers to tailor wastewater treatment processes. This research underscores the importance of sustainable practices in wastewater treatment, emphasizing the role of microbial degradation in addressing organic pollutant loads.

Optimization for Removal of COD and BOD through RSM-CCD by Activated Sludge Treatment Process for Pharmaceutical Wastewater

Wastewater generated from home and commercial operations is a polluting component of water. One of the main contributors for the production of wastewater by various manufacturing processes is the pharmaceutical industry. The commercial operations of industry are causing an increase in the amount of organic and inorganic contaminants, such as total suspended solids, chemical oxygen demand (COD) and biological oxygen demand (BOD). Activated sludge process reduces COD, BOD and Total Suspended Solids (TSS), with three input variables: pH, time and Mixed Liquor Suspended Solids (MLSS). The Central Composite Design-Response Surface Methodology (CCD-RSM) is used to optimize responses for COD and BOD removal efficiency. To achieve optimization results, numerous sets of trials were conducted for the input variables - pH (4.2–6.5), time (12–30 h) and MLSS (2520–4310 mg/l). The analyzed models were shown to be quadratic and highly significant by the F-value and P-value. The regression coefficients (R2) for the quadratic models developed for removal efficiency, COD, and BOD5 are 0.9996, 0.9995 and 0.9996, respectively. According to CCD-RSM, the optimal matching input factors for the greatest removal efficiency of BOD and COD were: MLLS = 3415 mg/l, time = 21 h and pH = 5.35. Using the traditional method, the maximum removal (95%) of BOD and COD was seen at pH = 6.5, time = 12 h and MLLS = 4310 mg/l.

Assessment of Rice Husk-Based Activated Carbon as Adsorbent in Domestic Wastewater Treatment

Indiscriminate discharge of wastewater into the environment is of utmost concern, especially in developing countries. This study evaluated the efficiency of rice husk based activated carbon in wastewater samples harvested from a students’ hostel and a restaurant within the Federal University of Technology, Akure. The adsorbent used was produced from rice husk using hydrogen tetraoxosulphate (VI) acid (H2SO4) as the activating agent. The aim of this study was to assess rice husk-activated carbon for the reduction of physicochemical parameters such as hardness, pH, biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved oxygen (DO), total dissolved solid (TDS), total suspended solid (TSS), and heavy metals which include chromium (Cr), lead (Pb), manganese (Mn), and iron (Fe). The wastewater samples were treated using activated rice hush ash of particle size (180 µm) at four different doses (30, 35, 40, 45 grams/400 ml). The results showed that the different doses of activated carbon had different removal efficiency. It was observed that the optimum dosage was 40g for DO, COD, BOD, and TDS while 30g was optimum for Hardness. It was also observed that an increase in the concentration of rice husk adsorbent led to an increase in the removal efficiency for the heavy metals (Cr, Mn, Pb, and Fe). The maximum percentage removal of DO, COD, BOD, TDS, and TSS, with rice husk was 21%, 58%, 72%, 21%, and 57% respectively. After the treatment of the domestic wastewater and comparing with the WHO standard, the treated wastewater quality was found to be safe for direct discharge into surface water bodies and irrigation purposes.

Polyethylene terephthalate cap‐based bioreactors for combined domestic and dye wastewater treatment

AbstractIn the current study, a sequencing batch reactor (SBR), a sequencing batch biofilm reactor (SBBR) and a moving bed biofilm reactor (MBBR) were designed and used to treat actual samples of combined domestic and dye (Congo red) wastewaters over a 10‐hour cycle. A new application of reusing plastic bottle caps in the SBBR and MBBR was examined. In the SBR, maximum chemical oxygen demand (COD) removal of up to 66% ± 3% was achieved after nine cycles of operation. In the SBBR, a rapid increase in COD removal efficiency was observed during the first cycle, with a noticeable improvement in performance in subsequent cycles, eventually reaching a maximum COD removal efficiency of 77% ± 3%. In the MBBR, maximum COD removal of up to 88% ± 3% was achieved after nine cycles of operation. The biodegradation occurred during two phases in the SBR and SBBR, as an anaerobic phase in the first 2 hours and then as an aerobic phase in the last 8 hours of operation; the MBBR operated in the fully saturated aerobic phase for 10 hours. Of the three reactors used, results for the MBBR in the fully aerobic condition by using polyethylene terephthalate caps as a biocarrier, demonstrated the optimum conditions under which to treat and biodegrade Congo red at all concentration in each cycle. The maximum removal efficiency, which equalled 99% ± 1%, was recorded at an optimal concentration of 50 mg/L. Additionally, five kinetic models were proposed to assess microbial growth activity, and the results demonstrated the elimination of toxic effects when using polyethylene terephthalate caps as biocarriers in the MBBR. The laboratory experiments were consistent with the Monod model.

Enhancing microbial fuel cell performance: A study on carbon cloth/TiO2 and carbon cloth/CuO electrodes

AbstractThis study confirmed the efficacy of modified electrode microbial fuel cells (MFCs) in removing chemical oxygen demand (COD) and generating electricity using wastewater from industrial meat processing. The findings of linear sweep voltammetry (LSV) and cyclic voltammetry (CV) demonstrated that applying CuO particles to carbon cloth (CC) significantly reduced the charge transfer resistance, resulting in improved electrochemical performance. In the batch experiment, the MFCs were conducted by applying different electrodes and Nafion‐117 as a proton exchange membrane (PEM). X‐ray powder diffraction (XRD), energy‐dispersive X‐ray analysis (EDAX) and scanning electron microscope (SEM) analyses were performed to study the development of metal oxide on the electrode surface. The MFC operating with the CC/CuO electrode achieved a maximum COD removal (74.6%), which was attained at the peak power output of 82.56 mW/m2 and the greatest current density of 213.33 mA/m2, as indicated by the polarization curve data. In light of these findings, coating CuO on the CC anode promotes electron transfer, enhances the electrode's conductivity and increases its electrochemical surface area. In summary, the findings of this study hold significant implications for sustainable electricity production and remarkable effects on environmental quality, highlighting the strategic importance of the research approach and outputs in addressing global energy and environmental challenges.