COD Removal Efficiency Research Articles

Performance of rice husk biocarrier on ammonia nitrogen removal in the MBBR treating aquaculture wastewater using biological attached growth process: Performance and kinetic study

This study investigates the feasibility of using rice husk (RH) as a cost-effective and environmentally friendly bio-carrier for immobilizing isolated microorganisms to treat synthetic recirculating aquaculture system (RAS) ‎wastewater. Two moving bed biofilm reactors (MBBR) inoculated with indigenous microorganisms were operated simultaneously for 391 days under various ‎cycle times and compared. The RH and Kaldnes-3 (K3) bio-carriers were placed in reactors R1 and R2, respectively.‎ The results indicated that at constant influent TAN, with increases in cycle ‎time from 6 to 24 h, TAN and COD ‎removal ‎efficiencies ‎increased in both bioreactors; but at an optimum cycle time of 6 h, the TAN and COD removal efficiencies were‎ ‎82 ± 1.5% ‎ ‎and‎ 77.9 ± 1.7%‎‎ for the R1 and, 89.9 ± 3.3%‎ ‎and ‎84 ± 1.2% ‎for the R2, respectively. Also, at a constant cycle time, ‎the performance of R2 was better ‎compared to R1 filled with RH. Microbial identification confirmed the presence of four dominant genera, including Arthrobacter, Bacillus, ‎Rhodococcus, and ‎Staphylococcus, which were heterotrophic nitrification bacteria (HNB). The TAN removal kinetics were investigated using a Modified Stover-Kincannon (MSK) model. In reactors R1 and R2, the biokinetic constants were determined to be Umax: 0.116 and 0.149 g/Lday, and KB: 0.158 and 0.182 g/Lday, respectively. The correlation coefficients (R2) of the MBBRs were higher than 0.97, indicating that the model adequately described the experimental data.

Comparative exploration of biological treatment of hydrothermal liquefaction wastewater from sewage sludge: Effects of culture, fermentation conditions, and ammonia stripping

Hydrothermal liquefaction wastewater from sewage sludge (sludge HTLWW) is an emerging waste stream that requires treatment before being discharged into the environment. Biological treatment of sludge HTLWW is an attractive option due to the low cost and operational flexibility. In this study, we investigated and compared the performance of three bacterial strains and four fungal strains for biodegradation of sludge HTLWW. Our screening experiments established pH and mineral supplementation (iron, magnesium, calcium, and phosphorus) conditions that greatly improved COD removal and chemical compound degradation by the microbes. An ammonia stripping pretreatment improved COD removal efficiency of Rhodococci jostii RHA1 by 44%. All tested bacterial strains can tolerate 10× dilution of HTLWW and remove 35–44% of COD in 2–15 days, while all tested fungal strains were able to tolerate 20× dilution and were better at degrading phenolic compounds than bacteria. HTLWW treatment with biomass pellets of fungus Aspergillus niger NRRL 2001 achieved the best COD removal efficiency of 47% in 12 days without the need of nutrient supplementation. Comparisons on chemical compound degradation by the tested microbes suggested that organic acids in HTLWW were highly degradable, followed by phenolic compounds. N-heterocyclic compounds were resistant to biodegradation and were removed by 38%. This study demonstrated pure culture biological treatment of sludge HTLWW with diverse types of microorganisms, which would guide the culture development and bioprocess parameter optimization for treating HTLWW of different compositions.

Identification, removal of microplastics and surfactants from laundry wastewater using electrocoagulation method

Microplastics (MPs) and surfactants are generally recognized as emerging contaminants with complicated ecotoxicological impacts. The majority of study data refers to laundry wastewater as a substantial source of MPs and surfactants in the aquatic system, which reaches aquatic environments through sewer discharges even when wastewater treatment facilities retain them. This study focused on releasing and removing contaminants from laundry wastewater, particularly MPs and surfactants. The electrocoagulation method was used to remove the pollutants from laundry wastewater. According to the results, a reference load of 2 kg of synthetic materials releases 92,700 to 1,14,300 synthetic microfibers (MFs). MFs, surfactants, and chemical oxygen demand (COD) removal efficiency are higher at neutral pH. The percentage removal efficiency of MFs, surfactants, and COD was 97.9%, 91.2%, and 86.3%, respectively, at an operating time of 25 min, a current density of 300 A/m2 with optimum power consumption. The total operation cost of laundry wastewater treatment by electrocoagulation was US$0.53 /m3. The readers will gain a complete understanding of the removal of MFs and surfactants from laundry wastewater using the electrocoagulation technique.

Applying a microbial electrolysis cell to promote imidacloprid removal in the adsorption biological coupling system at low temperature via accelerating coke regeneration and bioaugmentation

In this study, imidacloprid (IMI) wastewater was treated by adsorption biological coupling (ABC) and microbial electrolysis cell (MEC)-ABC technologies at low temperature (15 °C). Meanwhile, the degradation mechanism of IMI and the expression of functional genes were revealed. Results showed that under MEC enhanced treatment, the removal efficiency of COD, NH3-N, total-phosphorous (TP), and IMI reached 90.37 %, 92.03 %, 77.12 %, and 100 %, respectively, which were 9.71 %, 6.30 %, 9.48 % and 30.40 % higher than those of ABC treatment, respectively. Aestuariivirga sp. YIM B02566 became the dominant bacterium in ABC and MEC-ABC reactors under low-temperature conditions. MEC increased the relative abundance of Sphingomonadales, Hyphomicrobiales, and Aestuariivirga sp. YIM B02566 by 8.87 %, 16.15 %, and 5.29 %, respectively. Moreover, it up-regulated the abundance of key genes related to carbon and phosphorus metabolism, such as PGK (10.91 %), ENO (15.61 %), pstS (2.40 %), phnP (0.45 %) and phoD (0.97 %). Finally, MEC facilitated the conversion of C9H9ClN4 (m/z 209.0581), C9H11ClN4 (m/z 211.0729), C9H10ClN3O (m/z 212.0584), C9H11N5O2 (m/z 222.0964), C9H11ClN4O (m/z 227.0685) to C9H10ClN3O (m/z 212.0600), C9H11N5O2 (m/z 222.0964). The stability of MEC-ABC reactor operation at low temperature not only minimized the formation of IMI degradation products, but also provided an theoretical foundation for expanding the practical application of MEC-ABC technology in the treatment of IMI neonicotinoid insecticide wastewater.

Upgrade of the biggest catalytic ozonation wastewater treatment plant in China: From pollution control to carbon reduction

Catalytic ozonation is a widely used effective technology in advanced treatment for the removal of refractory organics from wastewater. However, it is also a highly energy-consuming technology, usually accounting for 30%∼40% of the total electricity consumption of a wastewater treatment plant (WWTP). The O3 consumption per unit of COD removed (g-O3/g-COD) is usually higher than 1.5 g-O3/g-COD, and the total carbon emission from catalytic ozonation is usually higher than 393.12 kgCO2 e/m3 of wastewater. In this study, we investigated an energy reduction strategy for the biggest catalytic ozonation WWTP, from laboratory-scale experimentation to corresponding engineering application. Laboratory-scale experiments showed that the mass transfer rate of dissolved O3 to the catalyst surface is crucial for COD removal efficiency. To improve the efficiency of catalytic ozonation, adding effluent backflow is a simple method that can enhance the removal of extracellular polymeric substances (EPS) from the catalyst surface and promote surface exposure. In the pilot-scale experiment (48 m3/d), when the backflow ratio increased from 0% to 100% (the optimal value), the proteins in EPS on the catalyst surface decreased significantly by 66.7%. The corresponding O3 consumption per unit of COD removed was reduced from 2.0 to 1.0 g-O3/g-COD. Furthermore, in the engineering application (52,000 m3/d) with a backflow ratio of 100%, the average effluent COD reduced from 52.0 to 43.3 mg/L, and the O3 consumption per unit of COD removed decreased from 0.98 to 0.69 g-O3/g-COD. In terms of carbon reduction, the indirect carbon emission reduction was approximately 3.0 × 103 t CO2 e/a. This study demonstrates the advantages of catalytic ozonation improvement and provides an engineering model of energy conversation and carbon emission reduction for over 35 similar WWTPs in China.

Effect of HRT on nitrogen removal from low carbon source wastewater enhanced by slurry and its mechanism

Insufficient carbon sources in low-carbon wastewater have consistently hindered nitrogen removal performance. This work utilized slurry after anaerobic digestion as an additional carbon source, and the optimal hydraulic retention time (HRT) parameters were obtained through adjustment. The findings revealed that, under HRT conditions of 24–12 h, the discharge standards of wastewater treatment plants (WWTPs) could be met. It had been proven that HRT 12 h was the more cost-effective parameter for application in WWTPs, and the removal efficiencies for COD, NH4+-N, NO3–-N, and TN reached impressive levels of 82.43%, 95.24%, 77.49%, and 86.70%, respectively. However, the HRT 6 h struggled to achieve efficient wastewater treatment. Mechanistic analysis demonstrated that shortening the HRT resulted in considerably higher microbial richness, diversity, and evenness, causing notable shifts in microbial community structure. Additionally, a shortened HRT reduced the enrichment abundance of key bacterial phyla (Proteobacteria, Bacteroidetes) and genera (Hydrogenophaga, Filimonas, Meganema) that played an important role in nitrogen and organic matter removal. Furthermore, a shortened HRT increased hydraulic shear forces, impeding the enrichment of carbon and nitrogen metabolism pathways, and reducing the abundance of essential genes associated with glycolysis (HK, pfkA, FBA, GAPDH) and nitrogen metabolism processes (narG, narH, narI, norB, nirS, nosZ). It was noteworthy that the microbial community under the HRT 6 h condition carried the highest risk of microbial pathogenicity. This work revealed the optimal parameters, and carbon and nitrogen metabolism mechanism of wastewater treatment systems with slurry as a carbon source for the first time, and provided novel ideas and insights for low-carbon wastewater treatment.

A sustainable nanotechnology producing high-quality remediated sewage wastewater used for microalgal protein-rich biomass and biodiesel production

AbstractWater scarcity is a crucial environmental challenge. Wastewater remediation is an important way to tackle the challenge. Using nanoparticles of natural and agricultural wastes is considered a low-cost sustainable remediation technology. This study develops an effective prototype of a sustainable sewage wastewater (SWW) remediation process using zeolite and bagasse nanoparticles. All studied physico-chemical parameters and heavy metals of the SWW were reduced over the course of treatment with nanobagasse (NB), nanozeolite (NZ), and nanobagasse-nanozeolite double treatments (DT). After only 2 weeks of remediation, the chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solid (TSS), and total dissolved solid (TDS) concentrations were decreased (in NB 38, 33, 58, and 30%; in NZ 40, 30, 63, and 58%; and in DT 47, 38, 75, and 62%), respectively, compared to raw SWW. The DT for 4 and 6 weeks (DT4W and DT6W) show 0.94 and 0.67 Kelly ratios, respectively, which are suitable for irrigation. According to the water pollution index (WPI), all types of DT treatments produce excellent-quality water. DT6W recorded the highest significant rank of removal efficiency of COD, BOD, TSS, TDS, PO4, NO3, Ca, Mg, Na, Cu, Cd, Fe, and Ni (72.7, 59.6, 88.6, 74, 56.7, 88.2, 72.7, 58.7, 80.7, 94.6, 91.1, 65.3, and 84.4%). This remediated water may be used directly for irrigation or other purposes. Also, this study proves that DT4W and DT6W are suitable for Chlorella sorokiniana growth and production of safe protein-rich biomass, 26 and 31.8% protein, respectively. DT for 2, 4, and 6 weeks are suitable growth media for C. sorokiniana to produce diesel engines’ compatible biodiesel. Finally, this recent study presents an interpretation of the physiological status of C. sorokiniana cells grown in the raw SWW and DT media.

Modelling selenite and chemical oxygen demand removal in an inverse fluidized bed bioreactor using genetic algorithm optimized artificial neural network

AbstractBACKGROUNDA genetic algorithm (GA) optimized artificial neural network (ANN) model was developed to simulate selenite removal efficiency (SRe) and chemical oxygen demand (COD) removal efficiency (CRe) in a single‐stage inverse fluidized bed reactor (IFBR) operated under different hydraulic retention time (HRT) (12–48 h), and inlet selenite concentration (12.7–635 mg L−1). Multi‐objective optimization for SRe and CRe with the ANN model was adopted to estimate the pareto optimal solutions in the bioreactor system.RESULTSGA optimized ANN topology suggested five neurons in the hidden layer, and the optimal data partitioning between training, test, and validation subsets (in 70:15:15 ratio) using cross‐validation. The average fitness for SRe and CRe of the resulting ANN model over training (R2 = 0.885), test (R2 = 0.967) and validation (R2 = 0.972) subsets were reasonably good. Sensitivity analysis suggested an increase in SRe and CRe with HRT, while an increase in inlet selenite concentration had a negative effect on SRe. Local interpretable model‐agnostic explanations and SHapley Additive exPlanations for the developed model suggested a positive coefficient of the predictors on CRe. Pareto optimal solution for SRe (92.87%–95.26%), and CRe (91.33%–99.35%) were suggested for HRT and inlet selenite concentration varying between 35.67 h and 36 h, and 0.1 g L−1 and 0.884 g L−1, respectively.CONCLUSIONSThe GA optimized ANN model could be exploited for the prediction of contaminant removal efficiencies in the bioreactor system with a fair degree of complexity (i.e., IFBR). Multiple objective pareto optimal solutions can identify the best operating conditions relevant for wastewater treatment. © 2023 Society of Chemical Industry (SCI).

Hydrogen peroxide assisted advanced electrocoagulation for reducing the organic content of leachate nanofiltration concentrate

Integrated biological treatment-membrane filtration is widely applied in leachate treatment to ensure discharge standards. The most important waste of this integrated application is high volumes of membrane concentrate. In this study, the treatment of leachate nanofiltration concentrate (NFC) with high resistive organic matter content was investigated by hydrogen peroxide (HP) assisted advanced electrocoagulation process (EC-HP) using Al electrodes. To achieve maximum pollutant removal efficiencies, process optimization was carried out using the Box-Behnken design (BBD). Statistically, the fit of the model was evaluated by analysis of variance. Correlation coefficients (R2) of all mathematical models developed for system responses (COD, UV254, TOC, and color removal efficiency) with EC-HP process were close to 1, adjusted R2 values were close to R2 values, and the difference between adjusted R2 and predicted R2 values was less than 0.2. These values indicate that the BBD method is effective, appropriate, and meaningful in explaining the pollutant removal from leachate NFC with the EC-HP process. Under the optimized conditions (27.3 mM HP, 0.6 A, pH 5, and 45 min) 62.2 %, 55.3 %, 73.9 %, and 85.9 % COD, TOC, UV254, and color removal efficiencies, respectively were predicted by the model and by validation study, 57.3 % COD, 52.0 % TOC, 68.3 % UV254, and 85.0 % color removal yields were achieved. SEC and SECCOD values were calculated as 7.65 kWh/m3 and 2.78 kWh/kgCOD, respectively at optimum conditions. Moreover, ENC, ELC, CC, and TC values were 0.55 $/m3, 0.82 $/m3, 8.0 $/m3, and 9.37 $/m3, respectively. The results of the study showed that the EC-HP process is an effective method for pollutant removal from leachate NFC.

Application of Attached Growth System for Laundry Wastewater Treatment

Laundry wastewater can be treated in a small-scale aerobic wastewater treatment (WWT) system utilizing a microbubble generator (MBG). However, removing pollutants, precisely chemical oxygen demand (COD), is often low, especially under high wastewater load conditions. This study aims to improve the WWT system’s performance by incorporating an attached growth system. The research was conducted in a small-scale WWT system with a volume of 832 L in Cokrodiningratan, Code Riverbank, Yogyakarta, treating real wastewater from a nearby laundry shop. Experiments were performed batch-wise for one week with suspended and nylon-fabric-attached growth systems. Wastewater samples from the WWT system were taken and analyzed for COD concentrations. Results indicate that the attached growth system outperforms the suspended growth system. During operation, the suspended growth system achieved a COD removal rate of approximately 78% (temperature range of 26-28°C, a pH level of 6.3-7.1, and influent COD: 377.5 mg/L). In contrast, with the introduction of attachment media under similar batch operation conditions (temperature range: 26-28°C, pH level: 6.4-7.4, influent COD: 755.5 mg/L), the COD removal efficiency increased to 94%. The incorporation of attachment media led to a notably stable performance outcome.

Simultaneous treatment of epichlorohydrin wastewater and polyhydroxyalkanoate recovery by halophilic aerobic granular sludge highly enriched by Halomonas sp.

The treatment of epichlorohydrin (ECH) wastewater exists chances for achieving cleaner production. This study initially employed moderately halophilic aerobic granular sludge (HAGS) to treat ECH wastewater, and the resulting HAGS was utilized to recover polyhydroxyalkanoate (PHA). During the acclimation process of HAGS, the chemical oxygen demand removal efficiency stabilized at 70 %. Moreover, due to the high enrichment of Halomonas sp. (relative abundance of 86 ± 0.50 %), the maximum PHA content of wasted HAGS was 52.67 wt% in the fermentation process. Simultaneously, the utilization of nuclear magnetic resonance spectroscopy (1H and 13C spectra) and fourier transform infrared spectroscopy for the structural analysis of polymers revealed that polyhydroxybutyrate was the predominant substance extracted from HAGS. In this study, the innovative use of highly enriched HAGS for treating ECH wastewater and simultaneously recovering PHA not only enables the efficient biological treatment of ECH wastewater but also realizes resource recovery of ECH wastewater.

Efficient treatment of surfactant containing wastewater by photocatalytic ozonation with BiPO4 nanorods

In this study, monoclinic BiPO4 nanorods were fabricated by one-pot solvothermal method. Its catalytic capability in photocatalytic ozonation process was tested by degradation and mineralization of sodium dodecyl benzene sulfonate (SDBS) solution. The results demonstrated that the TOC removal rate was dramatically improved to 90.0% at 75 min for UV/O3/BiPO4 process, which was 4.9 and 3.8 times more than that of UV/BiPO4 and O3. Moreover, the pseudo-first-order kinetic constant (0.337 min−1) and mineralization rate (90.0%) for SDBS degradation using BiPO4 in UV/O3 process were 1.6 and 1.3 times as great as that of conventional TiO2 photocatalyst (0.206 min−1, 67.3%). The influence of BiPO4 dosage, O3 concentration initial pH and coexisted ions on SDBS degradation in UV/O3/BiPO4 process were also investigated. The outcome of quenching studies illustrated both ·OH and h+ contributed prominently to SDBS degradation in UV/O3/BiPO4 process, implying that high valence band position of BiPO4 could promote the synergism between photocatalysis and ozonation. The degradation pathway of SBDS was proposed by combination of intermediates analysis and DFT calculation. Real carwash wastewater was chosen as typical surfactant containing wastewater to explore the practical application of UV/O3/BiPO4 technology. During 30 min, COD and LAS removal efficiency reached 59.7% and 70.6%, respectively. The quality indices of effluent could meet the requirements for reuse of carwash water in Water Quality Standard for Urban Miscellaneous Use in China. Energy consumption in the process was calculated as 13.9 kW h m−3, which was about 3.6 and 2.2 times less than that of UV/BiPO4 and O3 process, respectively. The results suggest that UV/O3/BiPO4 system has an application potential for surfactant containing wastewater treatment or recycle.

Performance improvement of microbial fuel cell using experimental investigation and fuzzy modelling

The yield of a microbial fuel cell (MFC) is significantly influenced by the media composition, which mainly consists of carbon, nitrogen sources and aeration rate. This study uses fuzzy modelling and optimization to enhance the performance of MFC. First, a simulation of the microbial fuel cell model using three input parameters—glucose (g/L), yeast extract (g/L), and aeration (ml/min)—was performed using experimental data sets. Three output parameters—power density (W/m2), COD removal (%), and coulombic efficiency (%)—are used to assess the performance. Then, the ideal values for three input controlling parameters are found using the salp swarm optimizer (SSO) for simultaneously increasing power density, COD elimination, and coulombic efficiency. For the fuzzy model of the power density, the RMSE values for the training and testing data sets are 1.35 e−07 and 0.0424, respectively. The R-squared values for training and testing are 1.0 and 0.98, respectively. Low RMSE values and high R-squared proved the accuracy of fuzzy model. Then using, SSA, the coulombic efficiency climbed from 38 % to 40.33 %, and the COD removal went from 80 % to 81.71 %. Under this condition, the performance index increased from 118.525 to 122.532 by around 3.4 %.

Effective remediation of leachate concentrate by peroxymonosulfate in a catalytic ceramic membrane filtration process: Performance and mechanism

Membrane concentrated landfill leachate has been characterized by complex component and degradation resistant. In this work, a new catalytic ceramic membrane (CuCM) was developed by in-situ integrating copper oxide in the membrane and used in combination with peroxymonosulfate (PMS) for leachate concentrate treatment. The performance and key factors of the CuCM/PMS system were systematically studied. Results showed that the CuCM/PMS system experienced promising efficiency in the pH range of 3 ∼ 11. The highest COD, TOC, UV254 and Color removal efficiency achieved by the CuCM-3/PMS system under the conditions of pH = 7.0 and CPMS = 10 mM, which reached up to 63.4%, 50.5%, 75.1% and 90.2%, respectively. The possible mechanism of leachate remediation was proposed and non-free radicals (Cu(Ⅲ), 1O2) played an important role in the CuCM/PMS system for leachate remediation. The fluorescence spectrum and GC–MS analysis showed that the refractory organics with a high molecular weight in the leachate concentrate were mostly oxidized into small molecules, which also alleviated the membrane fouling. In addition, the slight decrease in COD (7.4%) and TOC (9.7%) after 6 cycles revealed the good catalytic stability and reusability of CuCM-3/PMS. This work provides a feasible strategy for leachate concentrate remediation via a nonradical oxidation process.

Preparation of Ti4O7 Reactive Electrochemical Membrane for Electrochemical Oxidation of Coking Wastewater

The effluent of coking wastewater comprises hundreds of refractory organics and is characterized by high toxicity and non-biodegradation. Electrochemical advanced oxidation processes (EAOPs) have been widely applied in the field of water purification. In this study, a Ti4O7 reactive electrochemical membrane (REM) was prepared using the plasma spraying method for the electro-oxidation of coking wastewater. The composition and surface morphology of the Ti4O7 REM were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The computational fluid dynamics (CFD) simulation was used to compare the mass transfer performance of the Ti4O7 REM in traditional batch (TB) mode and flow-through (FT) mode. In the FT mode, the effects of current density and anode–cathode distance on the treatment efficiency were investigated, and the electrocatalytic performance of the anode on coking wastewater was analyzed. The results showed that the COD removal efficiency reached 76.2% with an energy consumption of 110.5 kWh kg−1 COD under the optimal condition. In addition, cathodic polarization provides an effective technique for maintaining the long-term activity of the Ti4O7 REM. The three-dimensional fluorescence results and UV-vis spectrum showed that the aromatic compounds could be effectively degraded using the Ti4O7 REM. The Ti4O7 REM demonstrated excellent performance of electrochemical oxidation and satisfactory stability, which had a strong potential for application in the field of practical wastewater and engineering practices that respond to the concept of sustainable development.

Potential positive effects of natural sunlight on a biological system for landfill leachate treatment

AbstractActivated sludge filtration performance is a significant mean to evaluate membrane fouling trend for wastewater treatment. Here the impact of sunlight irradiation on activated sludge filtration performance and microbial communities in sequencing batch reactors (SBRs) when treating raw landfill leachate were studied. The sludge in photic SBR (i.e., SBR exposed to natural sunlight) exhibited better filtration performance compared to dark SBR (i.e., SBR unexposed to sunlight). The removal efficiency of COD and NH4+‐N in the photic SBR were slightly higher than those in the dark SBR. The contents of the extracellular polymeric substances (EPSs) of sludge in both SBRs initially increased and then decreased. However, in the later period, the sludge filtration performance worsened due to the fungal activity in the dark SBR. Natural sunlight irradiation promoted sludge filtration performance by affecting the microorganism structure in the photic SBR. The bacterial genus Thauera was dominant in the photic SBR (39.35%), whereas Planktosalinus and Ottowia were dominant in the dark SBR (16.84% and 12.55%, respectively). Natural sunlight irradiation had a prominent effect on the fungal diversity in the system, and filamentous bulking caused by the fungi genus Trichosporon’s proliferation was observed in the dark SBR but not in the photic SBR, which also increased the polysaccharide content.

Evaluation of combined efficiency of conventional coagulation-flocculation process with advanced oxidation process (sulfate-hydroxyl radical) in leachate treatment

This study evaluated a novel municipal solid waste leachate (MSWL) treatment system called the Batch flow leachate treatment system (BFLTS). This process uses a combination of coagulation/flocculation (C-F), advanced oxidation (sulfate-hydroxyl radical), and extended aeration of activated sludge (EAAS) to treat MSWL. The results indicated that the primary treatment phase using coagulation/flocculation with 0.8 g L<sup>-1</sup> FeCl<sub>3</sub> at pH 6 achieved 67% turbidity and 63% chemical oxygen demand (COD) reduction. The secondary treatment phase with the presence of both K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> and H<sub>2</sub>O<sub>2</sub> peroxides was more efficient than single peroxide processes. While PS-based or H<sub>2</sub>O<sub>2</sub>-based single peroxide processes are less effective (UV-PS 65.7%, UV-H<sub>2</sub>O<sub>2</sub> 43.2%, Heat-PS 58.6%, Heat-H<sub>2</sub>O<sub>2</sub> 34.5%, and Heat-PS/H<sub>2</sub>O<sub>2</sub> 74.8%). The UV-PS/H<sub>2</sub>O<sub>2</sub> system achieved the highest COD removal rate of 89.4%. In the third treatment phase, the efficient removal of COD and Biochemical oxygen demand (BOD) under optimal operating conditions was 87.3% and 94.7% respectively. Overall, the BFLTS treatment system has demonstrated high efficiency in removing COD, BOD, TSS, Turbidity, TKN, and Heavy metals by 99%, 98%, 97%, 89%, 86%, and 98%, respectively. This hybrid process has potential for reducing organic load in MSWL and can be used for various leachates.

Enhanced production of biohydrogen and biomethane through a two-stage anaerobic fermentation of food waste mixed with conductive additives

This study was conducted to examine the effects of three different conductive materials (CMs) on H2 and CH4 production in a two-stage fermentation process (TSFP). This study also investigated the distinct roles played by the different types of CMs within the process. The study findings revealed that the combination of two or more CMs led to a significant improvement in production compared to using a single CM. Magnetite nanoparticle (MNP) played a crucial role in enhancing H2 productivity during the first stage of the TSFP. The TSFP with carbon nanotubes (CNT) + MNP demonstrated the highest H2 yield of 121 ± 7 mL/g·COD with the H2 production rate of 219 ± 18 mL/hr, followed by the TSFP with MNP alone yielded the second highest H2 of 81 ± 5 mL/g·COD with the H2 production rate of 169 ± 25 mL/hr. Both powdered activated carbon (PAC) alone (277 ± 17 mL/g·COD) and PAC + CNT (278 ± 15 mL/g·COD) showed the highest CH4 yield, indicating that PAC contributed to higher CH4 production in the second stage of the TSFP. The addition of PAC to the samples led to higher chemical oxygen demand (COD) removal efficiency in the TSFP, while the presence of MNP significantly increased the total energy production.

Electrochemical oxidation of azo dyes degradation by RuO2–IrO2–TiO2 electrode with biodegradation Aeromonas hydrophila AR1 and its degradation pathway: An integrated approach

Azo dyes are the most varied class of synthetic chemicals with non-degradable characteristics. They are complex compounds made up of many different parts. It was primarily utilized for various application procedures in the dyeing industry. Therefore, it's crucial to develop an economical and environmentally friendly approach to treating azo dyes. Our present investigation is an integrated approach to the electrooxidation (EO) process of azo dyes using RuO2–IrO2–TiO2 (anode) and titanium mesh (cathode) electrodes, followed by the biodegradation process (BD) of the treated EO dyes. Chemical oxygen demand (COD) removal efficiency as follows MB (55%) ≥ MR (45%) ≥ TB (38%) ≥ CR (37%) correspondingly. The fragment generated during the degradation process which was identified with high-resolution mass spectrometry (HRMS) and its degradation mechanism pathway was proposed as demethylation reaction and N–N and C–N/C–S cleavage reaction occurs during EO. In biodegradation studies by Aeromonas hydrophila AR1, the EO treated dyes were completely mineralized aerobically which was evident by the COD removal efficiency as MB (98%) ≥ MR (92.9%) ≥ TB (88%) ≥ CR (87%) respectively. The EO process of dyes produced intermediate components with lower molecular weights, which was effectively utilized by the Aeromonas hydrophila AR1 and resulted in higher degradation efficiency 98%. We reported the significance of the enhanced approach of electrochemical oxidation with biodegradation studies in the effective removal of the pollutants in dye industrial effluent contaminated water environment.

Embedded Graphite and Carbon Nanofibers in a Polyurethane Matrix Used as Anodes in Microbial Fuel Cells for Wastewater Treatment.

Composites of polyurethane and graphite and polyurethane and carbon nanofibers (PU/Graphite 0.5% and PU/CNF 1%) were synthesized and used as anodes in dual-compartment microbial fuel cells (MFCs) for municipal wastewater treatment; electrical energy generation and organic matter removal were assessed. The maximum power density, coulombic efficiency and chemical oxygen demand (COD) removal efficiency in the MFCs packed with the PU/Graphite 0.5% and PU/CNF 1% composites were 232.32 mW/m3 and 90.78 mW/m3, 5.87 and 4.41%, and 51.38 and 68.62%, respectively. In addition, the internal resistance of the MFCs with the best bioelectrochemical performance (PU/Graphite 0.5%) was 1051.11 Ω. The results obtained in this study demonstrate the feasibility of using these types of materials in dual-compartment MFCs for wastewater treatment with electric power generation.