Chemical Oxygen Demand Removal Rate Research Articles

Alleviating acid inhibition via bentonite supplementation during acidulated swine manure anaerobic digestion: Performance enhancement and microbial mechanism analysis

Swine manure is usually transmitted by the “collection-storage-transport” mode of the biogas project. However, this particular application pattern results in high volatile fatty acids (VFAs) concentration due to the long transition time in the “collection-storage-transport” process. In this work, acidulated swine manure anaerobic digestion (AD) with bentonite supplementation was firstly investigated with an expectation of acid alleviation, performance enhancement and microbial mechanism. Results indicated that the methane production rate in the 20 g/L bentonite-added digester was 2.87 fold higher than that of the control digester. Chemical oxygen demand (COD) removal rate was elevated by 140.1% via bentonite supplementation. Besides, the rapid decrease of VFAs and ammonia indicated that bentonite supplementation could offer buffering capacity and alleviate acid inhibition. Microbial community analysis revealed that acetoclastic methanogenesis (Methanosaeta and Methanosarcina) was the predominant methanogenesis pathway in this AD system. Syntrophic acetate oxidation (SAO) bacteria were discovered in the bentonite-added digester, and they converted acetate into H2/CO2 to support hydrogenotrophic methanogenesis. This study could offer guidance for acidulated swine manure AD in the practical biogas project.

A novel vortex flocculation reactor for efficient water treatment: Kinetic modeling and experimental verification

We designed a novel vortex flocculation reactor with column-cone-column structure by adding vortex generators to form the micro-vortices to improve the flocculation efficiency. The vortex generators, actually wedge-shaped baffles, act as turbulence components to generate large flow resistance, thus reducing the size of the vortex to approach that of the floc. The inverted cone-cone-inverted cone structure in small-vortex flow flocculation zone prompts the fluid to form boundary layer dissociation phenomenon, thereby enhancing the relative motion of floc particles. The numerical simulation results of flow field structure indicated that the fluid presented a multiphase flow of “swirl flow-vortex flow-plug flow”; hence the fluid characteristic changed step by step. Moreover, the multistage velocity gradient of the fluid in different flow layers enhanced the probability of floc particles collision, thus strengthening the flocculation. Then the lab-scale vortex flocculation reactor was manufactured to conduct flocculation tests. The results revealed that the vortex flocculation reactor took the reaction time of only 10 s to achieve a superior chemical oxygen demand removal rate of 93.7%. The vortex flocculation reactor, based on the multiphase flow and multistage velocity gradient reinforcement flocculation strategy, can offer an effective way to improve the flocculation efficiency.

Biomass juncus derived carbon modified with Fe3O4 nanoparticles toward activating peroxymonosulfate for efficient degradation of tetracycline

In this work, Fe3O4 nanoparticles anchored biomass juncus derived carbon (Fe3O4@JDC) was developed as a highly efficient heterogeneous peroxymonosulfate (PMS) activator to degrade organic pollutants. As-prepared catalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometer techniques. High loading and good dispersion of Fe3O4 nanoparticles on JDC lead to excellent degradation performance for tetracycline (90.2 %, 60 min) and other pollutants (above 80 %), and the reaction rate constant (k) is 3.73 times (0.0384 min−1) than that of pure JDC (0.0103 min−1) in the presence of PMS. Additionally, chemical oxygen demand (COD) removal rate of Fe3O4@JDC/PMS system (64.7 %, 60 min) is best than other systems (JDC system, JDC/PMS system, etc.). The quenching tests and electron paramagnetic resonance (EPR) data further demonstrate that TC degradation is an integrative contribution of both non-radical (1O2) and free radical (O2−, SO4−, and OH) pathways. Furthermore, Fe3O4@JDC also exhibits superior reusability (81.1 % degradation efficiency after five cycles) and magnetic separation ability.

In-situ activation of Fe78Si9B13 metallic glasses for electro-Fenton degradation of industrial oily wastewater

Metallic glasses (MGs) with superior catalytic properties have attracted widespread attention towards organic wastewater remediation. However, the low degradation efficiency of industrial oily wastewater by the conventional ways and materials hinders practical applications. Herein, Fe78Si9B13 MGs as highly efficient electrodes exhibit excellent catalytic performance for electro-Fenton degradation of oily wastewater for the first time. The oil removal rate and chemical oxygen demand (COD) removal rate are as high as 81.8% and 77.3% within 120 min under optimum experimental parameters. Compared to other electrode materials, Fe78Si9B13 MG electrodes possess the more preferable catalytic capability. Additionally, two degradation processes related to direct oxidation of electrochemical action and mediated oxidation of activated radicals may be accurately certified. These findings will develop a functional material and provide a potential approach for environmental applications of purification of refractory organic contaminants.

Carbon Microspheres Composite PbO2 Anode to Enhance Electrode Activity for Degradation of Isopropylantipyrine: Kinetics and Mechanism

An innovative CMS-PbO2 electrode was fabricated by combining hydrothermally synthesized carbon microspheres (CMS) on a PbO2 electrode by electrodeposition. Using the CMS-PbO2 electrode, the main factors affecting Isopropylantipyrine (PRP) degradation were studied. Under optimum process conditions, the concentration of PRP was 50 mg l−1, the applied current density was 30 mA cm−2, the electrolyte (Na2SO4) concentration was 0.1 mol l−1, and pH was 7. The PRP degradation rate reached 100%, and chemical oxygen demand (COD) removal rate reached 43.42% after 120 min of electrochemical oxidation. Using field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy, the electrochemical performance of the two electrodes was discussed. The composite of carbon microspheres successfully improved the electrochemical activity of the electrode and its conductivity. Furthermore, the ability of the two electrodes to generate hydroxyl radicals was compared and the possible degradation pathway of PRP was considered. In addition, electrode stability and safety were evaluated by accelerated lifetime experiments and detection of lead ions in solution after electrochemical oxidation. The CMS-electrode was more stable and safer than the PbO2 electrode. The CMS-PbO2 electrode provides a new strategy for the treatment of pharmaceutical wastewater.

Study on preparation of a novel needle coke heterogeneous electro-Fenton cathode for coking wastewater treatment

Coking wastewater is a major challenge in wastewater treatment because of its complex composition, high pollutant concentrations, and poor biodegradability. In this study, a novel electro-Fenton cathode was prepared from needle coke loaded with ferrous ions (Fe/NC/Ti) for use in a heterogeneous electro-Fenton system for coking wastewater treatment. The optimum preparation conditions of the electrode and the main factors affecting the treatment of coking wastewater were investigated. An effective method to reduce the energy consumption of the electro-Fenton system was sought by constructing variable current systems, and scale-up experiments were performed. When the catalyst-to-binder ratio was 3:1, Fe2+ loading was 2.5 %, and the calcination temperature was 400 °C, the Fe/NC/Ti cathode had the best catalytic effect. The chemical oxygen demand (COD) removal rate of the coking wastewater reached 97.7 %, and UV254 decreased from 0.163 to 0.037 under optimal conditions. The water was clarified and made transparent after the reaction. A series of characterizations confirmed that the Fe/NC/Ti cathode had good stability and electrochemical performance, and the electro-Fenton system constructed using the cathode degraded aromatic compounds in coking wastewater, such as phenols and cyclic macromolecular organic compounds, to small molecules and even caused full mineralization. The results of the scale-up experiment showed that the system had low energy consumption while maintaining high COD removal efficiency. Therefore, the Fe/NC/Ti cathode could be used as a potential solution to address the limitations of the traditional electro-Fenton process for coking wastewater degradation.

Direct start-up of aerobic granular sludge system with dewatered sludge granular particles as inoculant

Aerobic granular sludge (AGS) is a promising technology for engineering applications in the biological treatment of sewage. New objective is to skip the conventional granulation step to integrate it into a continuous-flow reactor directly. This study proposed a method for integrating spherical pelletizing granular sludge (SPGS) into a new patented aerobic granular sludge bed (AGSB), a continuous up-flow reactor. AGSB system could be startup directly, and after 120 days of operation, the SPGS maintained a relatively intact spherical structure and stability. With an initial high chemical oxygen demand (COD) volume loading of over 2.0 kg/(m3·d), this system achieved the desired effect as the same as a mature AGS system. The final mixed liquid suspended solids, and the ratio of 30 min–5 min sludge volume index (SVI30/SVI5) were 20,000 mg/L, and 0.84, respectively. Although hydraulic elution and filamentous bacteria (FBs) had a slightly negative impact on initial phase pollutant removal, the final removal rates for COD, total nitrogen (TN), ammonia nitrogen (NH4+-H), and total phosphorus (TP) were 90%, 70%, 95%, and 85%, respectively. The presence of specific functional microorganisms promoted the secretion of extracellular polymeric substances (EPS), from 90.65 to 209.78 mg/gVSS. The maturation process of SPGS altered the microbial community structures and reduced the species abundance of microbes in sludge.

Fe-Mn-Cu-Ce/Al2O3 as an efficient catalyst for catalytic ozonation of bio-treated coking wastewater: Characteristics, efficiency, and mechanism

It is important to develop a catalyst that has high catalytic activity and can improve the degradation efficiency of refractory organic pollutants in the catalytic ozonation process. In this study, Fe-Mn-Cu-Ce/Al2O3 was synthesised via impregnation calcination for catalytic ozonation of bio-treated coking wastewater. The physical and chemical characteristics of the catalysts were analysed using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller nitrogen adsorption–desorption methods. The effects of catalyst dosage, pH, and reflux ratio on the degradation efficiency of wastewater were examined in laboratory-scale experiments. The chemical oxygen demand (COD) removal rate of bio-treated coking wastewater was estimated to be 52.76 % under optimal conditions. The experiments on the catalytic mechanism demonstrated that the surface hydroxyl formed by the Lewis acid sites on the surface of the catalyst can react with ozone as the active site forming the active oxygen (·OH, ·O2–, and 1O2), thereby efficiently degrading the organic pollutants in coking wastewater. Furthermore, a pilot-scale experiment on the catalytic ozonation of bio-treated coking wastewater was carried out using an Fe-Mn-Cu-Ce/Al2O3 catalyst, while the effects of the initial pollutant concentration, ozone concentration, and gas flow on the COD removal rate were studied on a pilot scale. It was found that the COD removal rate of the wastewater was ∼ 60 % under optimal parameters. After the treatment, the wastewater steadily reached the coking wastewater discharge standard (COD < 80 mg/L), while the operating cost of catalytic ozonation reached ∼ 0.032$/m3, thereby paving the way toward economic engineering applications. The COD degradation kinetics in the bio-treated coking wastewater followed pseudo-second-order kinetics. Three-dimensional fluorescence and gas chromatography–mass spectrometry revealed that macromolecular organic pollutants in the bio-treated coking wastewater were greatly degraded. In summary, Fe-Mn-Cu-Ce/Al2O3 exhibited good reusability, high catalytic activity, and low cost and has a wide application prospect in the treatment of coking wastewater.

The Utilization and Modeling of Photo‐Fenton Process as a Single Unit in Textile Wastewater Treatment

AbstractStudies on the direct application of the photo‐Fenton process (PFOP) to disinfect and decontaminate textile wastewater are rare. The output of the artificial neural network (ANN) models applied to the wastewater of a textile factory producing woven fabrics, which is used to assess the efficiency of the PFOP process, are investigated and compared with each other in this study. The highest PFOP efficiency is obtained at a pH of 3. Chemical oxygen demand (COD), suspended solids (SS) and color removal rates are 94%, 90%, and 96%, respectively. The data are modeled with ANNs and nonlinear external input autoregressive ANNs (NARX‐ANN) using the MATLAB R2020a software program. Both Levenberg–Marquardt (trainlm) and scaled conjugate gradient (trainscg) algorithms are employed in the ANN and NARX‐ANN models, whereas hyperbolic tangent sigmoid (Tansig) and logistic sigmoid (Logsig) functions are superimposed on the hidden layer in the ANN model, and Tansig functions are superimposed on the NARX‐ANN model. It is determined that the developed ANN models are more effective in estimating the PFOP efficiency. The mean squared error is 0.000 953, and the coefficient of determination (R2) is 0.96 661.

Fabrication of Ru/Ir doped TiO2 electrode for electrocatalytic degradation of phenol

AbstractElectrocatalytic oxidation technology has been proved as an efficient method for degradation in organic wastewater. The service lifetime and degradation efficiency of the electrode, one crucial struggle, limits the broad application of electrocatalytic oxidation technology. Herein, a Ru/Ir doped TiO2 electrode with a long service lifetime was developed. Accelerated life experiment showed that the service life of an electrode was 33 h when the concentration of sulfuric acid was 1 M and the current density was 2000 mA·cm−2. The influence on the phenol degradation was evaluated by researching the operating parameters. In particular, the possible mechanism of phenol removal at different pH is elucidated. It is found that acidic environment is favorable for chemical oxygen demand (COD) and phenol removal at a current density of 20 mA·cm−2, pH 3 at 800 ppm NaCl, which can make the removal rates of phenol and COD with Ru/Ir doped TiO2 anode up to 97.21% and 100%. In addition, it was demonstrated that the hydroxyl radicals play a foremost role in the degradation of phenol. Given the well stability and high service life, the Ru/Ir doped TiO2 electrode holds promise for further industrial application in wastewater treatment.

The effect of interlayer water of metal-modified montmorillonite for catalytic ozonation

The catalytic ozonation-based advanced oxidation process (AOP) is applied to remove nondegradable chemical oxygen demand (COD), while the application in industry is limited by the economics and activity of catalysts. In this study, we demonstrate that by taking atrazine (ATZ) as a model pollutant, the removal rates of catalytic ozonation were negatively correlated with the interlayer water content of metal-modified montmorillonite (Mx@MMT), instead of the loadings metals. Among the modified MMT, Zn0.1@MMT achieved 83.2% degradation of ATZ within 15 min, and corresponding removal rates of COD and total organic carbon (TOC) reached 40.3% and 46.5%, respectively. Detailed EPR and quenching experiments identified that hydroxyl radicals (HO•) were the main reactive oxygen species and QTOF/MS/MS analysis helped to propose a possible degradation pathway of ATZ. Moreover, the catalytic performance of Zn0.1@MMT under different conditions was also systematically evaluated.

Effect of pistachio shell as a carbon source to regulate C/N on simultaneous removal of nitrogen and phosphorus from wastewater

Acid-pretreated pistachio shells were used as carbon sources to investigate the effects of carbon source dosage on simultaneous nitrogen and phosphorus removal under different carbon/nitrogen (C/N) ratios (7, 9, and 11). Results showed that C/N was positively correlated with mixed liquor suspended solids (MLSS) (R2 = 0.998, p < 0.01) and f value (R2 = 0.975, p < 0.05). Moreover, it was negatively correlated with the sludge volume index (SVI) (R2 = − 0.959, p < 0.05). C/N was also significantly negatively related to chemical oxygen demand removal rate (R2 = − 0.986, p < 0.05) and positively related to ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) removal rate (p < 0.05), the correlation coefficients were 0.992, 0.990 and 0.994, respectively. In the reactor with C/N of 11, the MLSS concentration and f value were the highest, the SVI was the lowest, and the removal efficiencies of NH4+-N (85.49 % ± 1.96 %), TN (84.19 % ± 1.42 %) and TP (94.10 % ± 1.67 %) were the highest. Furthermore, the relative abundance of denitrifying bacteria was the highest in the reactor. The abundance of nitrifying bacteria and phosphorus-removal bacteria was also relatively high.

One-piece adhesive-free molding polyvinylidene fluoride @Ag nanofiber membrane for efficient oxygen reduction reaction in microbial fuel cells

The electrode and catalyst are the keys to the structure and function of the microbial fuel cell (MFC). Conventional electrodes require the use of a binder to integrate the catalytic layer of different materials with the collector layer. Here, by using a simple three-step method and polydopamine (pDA) as an anchor point, the silver is successfully anchored to polyvinylidene fluoride (PVDF) nanofibers to prepare a new PVDF@Ag nanofiber membrane (NM) electrode. This method breaks the current strategy of using carbon cloth as a carrier and coating catalyst materials on it to fabricate MFC cathodes. By using PVDF@Ag NM in MFC, the role of Ag as a catalyst can reach a power density level of 72% of commercial Pt/C (20% Pt). The chemical oxygen demand (COD) removal rate of MFC can reach 57.44% (16.76% higher than Pt/C), and the coulombic efficiency (CE) can reach 25.7%. This one-piece adhesive-free molding MFC cathode innovatively and tightly combines the current collector and the catalytic layer for the first time, providing a brand-new form of MFC cathode in the future.

Highly efficient activation of peroxymonosulfate by biomass juncus derived carbon decorated with cobalt nanoparticles for the degradation of ofloxacin

The cobalt nanoparticles decorated biomass Juncus derived carbon (Co@JDC) was prepared by facile calcination strategy and applied to activate peroxymonosulfate (PMS) for eliminating ofloxacin (OFX) in the water environment. The results of catalytic experiments show that 97% of OFX degradation efficiency and 70.4% of chemical oxygen demand removal rate are obtained within 24 min at 0.1 g L−1 Co@JDC, 0.2 g L−1 PMS, 20 mg L−1 OFX (100 mL), and pH = 7, which indicates that Co@JDC/PMS system exhibits excellent performance. Meanwhile, the experimental results of affect factor show that Co@JDC/PMS system can operate in a wider pH range (3–9) and Cl−1, NO3−1, and SO42− have an ignorable effect on OFX degradation. The radical identification experiments confirm that SO4˙−, ·OH, O2˙−, and 1O2 are involved in the process of PMS activation, especially SO4˙− and 1O2 are the main contributors. Furthermore, a possible PMS activation mechanism by Co@JDC was proposed and the degradation pathways of OFX were deduced. Finally, the stable catalytic activity, negligible leaching of Co2+, and the outstanding degradation efficiency for other antibiotics prove that Co@JDC possesses good stability and universality.

Enhanced performance of microbial fuel cells with a bacteria/shape-controllable aligned carbon nanofibers hybrid biofilm

Improving the bacterial loading contents and extracellular electron transfer (EET) efficiency are promising strategies to enhance the overall performance of microbial fuel cells (MFCs). Herein, an aligned carbon nanofiber-bacteria (ACNF-bacteria) hybrid is prepared and used as an efficient anode employing the electrospinning and co-filtration method. The ACNF matrix reveals rich porous structure, large specific surface area, and obviously improved electrocatalytic performance compared to the pristine carbon cloth (CC) anode. Specifically, MFC with the ACNF-bacteria anode achieves a maximum power density of 704 mW m−2, which is 1.7, 2.1 times higher than that of ACNF, CNF and CC anode. Impressively, the coulombic efficiency and chemical oxygen demand (COD) removal rate for ACNF-bacteria anode reach 47.4% and 87.9%, respectively, far exceeding the CC anode (29.3% and 47.6%). Considering all the factors of low cost, facial fabrication, and high-power output, this novel ACNF-bacteria anode provides great potential for high-performance and cost-effective MFCs in a large scale.

Enhanced anaerobic digestion for degradation of swine wastewater through a Fe/Ni-MOF modified microbial electrolysis cell

Stainless steel mesh, as the common cathode of microbial electrolytic cell-assisted anaerobic digestion (MEC-AD), has the disadvantages of low specific surface area, poor biocompatibility and low catalytic activity, which limits the production of methane. Metal-organic frameworks (MOFs) have attracted much attention due to their adjustable pores and specific catalytic properties. However, little attention was paid to the combination of MOF and stainless-steel mesh to improve the performance of MEC-AD cathode. In this study, we combined stainless steel mesh with bimetallic MOF catalyst (Fe/Ni–NH2BDC) to prepare a composite cathode, and verified its promoting effect on AD of swine wastewater. The experimental results showed that the reactor with the carbonized MOF composite cathode (FeNi2-PAN2) achieved the highest soluble chemical oxygen demand removal rate of 82.92% and a maximum cumulative methane yield of 213.47 mL CH4/g COD under an applied voltage of 0.8 V, which were 33.14% and 57.56% higher than those of an anaerobic digestion (AD) control reactor, respectively, and higher than those of a carbon paper (CP) cathode reactor. The enrichment of Methanobacterium and Methanoculleus on the surface of FeNi2-PAN2 cathode surface indicated that FeNi2-PAN2 cathode enhanced hydrogenotrophic methanogenesis and improved the stability of AD.

Sustainable reuse of nickel converter slag as a heterogeneous electro-fenton catalyst for treating textile dyeing wastewater: Activity, mechanism and stability assessment

The high production and improper disposal of nickel converter slag (NCS) are raising serious concerns about its environmental impact, owing to the waste of resources and the foregone contribution to air, soil and groundwater pollution. This work uncovered that NCS could be reused as a superior catalyst for the treatment of textile dyeing wastewater by the heterogeneous electro-Fenton (hetero-EF) process. The NCS-laterite porous ceramsite (NLPC) catalyst showed the highest activity when the ratio of NCS to laterite was 3:2 and calcined at 900 °C. The methylene blue (MB) removal rate and chemical oxygen demand (COD) removal rate were 98.64% and 87.84%, respectively, after 30 min reaction under optimal operating parameters (100 g L−1 NLPC, 4 V of cell voltage and initial pH 3.0). Compared with the electro-Fenton (EF) system without NLPC catalyst, the degradation rate constant was increased by 223.9% (0.0452–1.464 min−1) and the energy consumption was reduced by 65.84% (2.02–0.69 kWh m−3). After six cycles, the MB removal rate only decreased by 5.35%, and the NLPC mass loss rate was 2.04%. Synergies between Co, Ni, Fe and Cu species to promote reactive oxygen species (ROS) generation were the predominant catalytic mechanism. Two possible pathways of MB degradation were deduced. In addition, the NLPC catalyst also showed excellent effects in different wastewater treatments. This work demonstrated an upgrade strategy for cleaner production of non-ferrous metallurgical by-products.

A revolving algae biofilm based photosynthetic microbial fuel cell for simultaneous energy recovery, pollutants removal, and algae production.

Photosynthetic microbial fuel cell (PMFC) based on algal cathode can integrate of wastewater treatment with microalgal biomass production. However, both the traditional suspended algae and the immobilized algae cathode systems have the problems of high cost caused by Pt catalyst and ion-exchange membrane. In this work, a new equipment for membrane-free PMFC is reported based on the optimization of the most expensive MFC components: the separator and the cathode. Using a revolving algae-bacteria biofilm cathode in a photosynthetic membrane-free microbial fuel cell (RAB-MFC) can obtain pollutants removal and algal biomass production as well as electrons generation. The highest chemical oxygen demand (COD) removal rates of the anode and cathode chambers reached 93.5 ± 2.6% and 95.8% ± 0.8%, respectively. The ammonia removal efficiency in anode and cathode chambers was 91.1 ± 1.3% and 98.0 ± 0.6%, respectively, corresponding to an ammonia removal rate of 0.92 ± 0.02 mg/L/h. The maximum current density and power density were 136.1 mA/m2 and 33.1 mW/m2. The average biomass production of algae biofilm was higher than 30 g/m2. The 18S rDNA sequencing analysis the eukaryotic community and revealed high operational taxonomic units (OTUs) of Chlorophyta (44.43%) was dominant phyla with low COD level, while Ciliophora (54.36%) replaced Chlorophyta as the dominant phyla when COD increased. 16S rDNA high-throughput sequencing revealed that biofilms on the cathode contained a variety of prokaryote taxa, including Proteobacteria, Bacteroidota, Firmicutes, while there was only 0.23–0.26% photosynthesizing prokaryote found in the cathode biofilm. Collectively, this work demonstrated that RAB can be used as a bio-cathode in PMFC for pollutants removal from wastewater as well as electricity generation.

Emulsified oil removal from steel rolling oily wastewater by using magnetic chitosan-based flocculants: Flocculation performance, mechanism, and the effect of hydrophobic monomer ratio

Large amounts of wastewater that contained emulsified oil were generated in the steel rolling process of the steel industry. The weak interaction between flocculants and emulsified oil and the slow floc separation are the main bottleneck in oily wastewater treatment. To solve this problem, this study successfully prepared three magnetic chitosan-based flocculants (MCS) with different hydrophobic monomer contents to treat steel rolling oily wastewater (SROW). The oil content, turbidity, chemical oxygen demand (COD), and UV254 removal rates were investigated by using MCS and compared with commercial flocculants. Results showed that as the dosage was 6 mL/L, MCS-2 had an optimal effect on oil and turbidity removal with 95.79 % and 87.85 %, respectively. The best COD removal rate of 66.67 % was achieved at a dosage of 4 mL/L with MCS-3. GC–MS analysis showed that the removal efficiency of MCS on alkanes was significantly better than that of aromatic hydrocarbons. Density functional theory calculations demonstrated that the hydrophobic groups of MCS can combine alkanes and aromatic hydrocarbons through hydrophobic association. Furthermore, charge neutralization, hydrophobic association, and adsorption bridging contributed to emulsified oil removal synthetically. The increased content of hydrophobic monomers enhances the interaction between flocculants and emulsified oil, which was significant for SROW treatment.

Development, performance evaluation, and kinetic studies of microbial fuel cell based auto dripping bioelectrochemical reactor (AutoDriBER) for urine treatment

ABSTRACT A bioelectrochemical reactor is an assembly, which facilitates energy generation and resource recovery using electrochemically active microorganisms. To maximise energy production from wastewater in this bioreactor system special design is required. Therefore, in the present study, continuous flow auto dripping bioelectrochemical reactors (AutoDriBERs) were developed as a single and multi-electrode assembly for urine treatment. Further, their performance was assessed by connecting reactors in series and parallel arrangements. AutoDriBER configured in series connection showed the highest 93.64 ± 1.57% chemical oxygen demand removal rate with the 1.38 ± 0.64 V voltage and 2.54 W m−3 polarisation power density. The optimum flow rate for maximum voltage production was tested with various models i.e. the linear, exponential, Sweibull-1, and Sweibull-2 models to confirm voltage prediction and its validity. The Linear and exponential models were found best fitted for voltage production with R 2 value of 0.999. These findings infer a novel approach toward optimisation of the complex, inexpensive and self-sufficient design for electricity generation from energy-rich urine wastewater in rural areas.