Highest Chemical Oxygen Demand Removal Efficiency Research Articles

Hybrid Sono-Electrocoagulation Process for the Treatment of Landfill Leachate Wastewater: Optimization through a Central Composite Design Approach

The effectiveness of the process of ultrasonication (US), electrocoagulation (EC) and hybrid sono-electrocoagulation (US+EC) on landfill leachate wastewater treatment was evaluated based on the removal efficiency of % color and % Chemical Oxygen Demand (COD) along with power consumption. The experimental results showed that the hybrid US+EC had a high color (100%) and COD (94%) removal efficiency with a lower power consumption of 4.50 kWh/m3 compared to the individual EC and US processes. In this hybrid US+EC process, the effects of various operating parameters were investigated and optimized using Design-Expert (12) based on the central composite design approach. The optimization results indicated a maximum COD removal efficiency of 71.05% with a minimum power consumption of 2.33 kWh/m3 at the following optimal experimental conditions: electrolyte concentration (X1) = 0.76 g/L, current density (X2) = 2.75 A/dm2, COD concentration (X3) = 3919.50 mg/L, sonication power (X4) = 100 W and treatment time (X5) = 36.05 min. The synergistic effect was calculated using the US, EC and US+EC process based on the % COD removal efficiency and has a positive effect of 20.51%. The % COD and % color removal efficiency were analyzed using a closed reflux method and UV-VIS spectrophotometer. Thus, the hybrid US+EC process, significantly enhances the efficiency of pollutants removal from landfill leachate wastewater.

Discerning realizable advantages of microbial electrochemical system towards raw municipal wastewater treatment: From the analyses of mass and energy flow

The low-cost biocathode microbial electrochemical system (MES) with microbial separator (MS) is promising for the practical application in wastewater treatment. To evaluate the potential realizable advantages for future full-size MESs, four 2-Liters MES modules with MS are constructed and their energy conversion, biomass metabolism and pollution degradation are systematically investigated. The mass and energy flow for MES with raw domestic wastewater is built under maximum power point (Pmax), maximum current point (Imax), and open circuit (OC) modes. The chemical oxygen demand (COD) removal rates are 0.831 and 0.846 kg m−3 day−1 in Pmax and Imax modes, while that of OC is 0.609 kg m−3 day−1. The effluent COD concentrations at Pmax and Imax are stable at 41 ± 2 and 37 ± 2 mg L−1, while that of OC is up to 101 ± 4 mg L−1. The observed sludge yield is only 23.4% (Pmax) or 19.5% (Imax) of the OC mode with much higher sludge calorific values. For the raw wastewater treatment, the direct electricity harvest and reuse from MES units are unrealistic and uneconomical due to its low energy efficiency. But the high COD removal efficiency and low observed sludge yield are the realizable advantages for practical applicated MESs.

Pilot-Scale Investigation of the Integrated Anaerobic–Aerobic Bioreactor (IAAB) Treating Palm Oil Mill Effluent (POME): Startup and Performance Evaluation

The treatment of palm oil mill effluent (POME) has always been the topic of research in Malaysia due to the high concentration of total suspended solid (TSS) and oil and grease (O&G) ranges from 28 846 to 30 920 mg/L and 5614 to 8812 mg/L, respectively. Additionally, the release of methane gas during the treatment of POME in all of the palm oil mills has been the major contributor to greenhouse gas (GHG) effect. The main aim of this work is to evaluate the performance of the pilot-plant integrated anaerobic–aerobic bioreactor (IAAB) for POME treatment at two different phases: (a) startup and (b) long-term performance evaluation from an organic loading rate (OLR) of 10.5 to 32.5 gCOD/(L·day). Startup of the pilot-plant IAAB was successfully accomplished in 24 days with overall removal efficiencies in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solid (TSS) of at least 90% at the OLR of 8.0 gCOD/(L·day). The pilot-plant IAAB achieved high BOD, COD, and TSS removal efficiencies of more than 99% for OLR up to 30.0 gCOD/(L·day) with methane yield ranges from 0.0406 LCH₄/gCODᵣₑₘₒᵥₑd to 0.1312 LCH₄/gCODᵣₑₘₒᵥₑd. The effluent quality remained stable with BOD of 16–107 mg/L with a high percent of compliance with the discharge limit of 100 mg/L. The coupling of the Grau second-order and Stover–Kincannon models (anaerobic system) with the Stover–Kincannon model (aerobic system) will completely define the pilot-plant IAAB system. This pilot-plant research will provide valuable data and experiences required to design and commission a full-scale IAAB.

Pollutants removal, greenhouse gases emission and functional genes in wastewater ecological soil infiltration systems: influences of influent surface organic loading and aeration mode.

The influences of influent surface organic loading rate (SOLR) and aeration mode on matrix oxygen, organic matter, nitrogen, phosphorus removal, greenhouse gases emission and functional gene abundances in lab-scale wastewater ecological soil infiltration systems (WESISs) were investigated. In WESISs, intermittent or continuous aeration improved oxygen supply at 50 cm depth and hardly changed anaerobic condition below 80 cm depth, which enhanced chemical oxygen demand (COD), NH4+-N, total nitrogen (TN) removal, the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, qnorB, nosZ genes and reduced CH4, N2O conversion efficiencies with SOLR of 16.9 and 27.6 g BOD/(m2 d) compared with non-aeration. Increased SOLR resulted in high TN removal, low N2O emission in aeration WESIS, which was different from non-aeration WESIS. High average COD removal efficiency of 90.7%, NH4+-N removal efficiency of 87.0%, TN removal efficiency of 84.6%, total phosphorus (TP) removal efficiency of 93.1% and low average N2O emission rate of 12.8 mg/(m2 d) were achieved with SOLR of 16.9 g BOD/(m2 d) in intermittent aeration WESIS. However, continuous aeration WESIS obtained high average removal efficiencies of 90.1% for COD, 87.5% for NH4+-N, 84.1% for TN, 92.9% for TP and low average emission rate of 13.1 mg/(m2 d) for N2O with SOLR of 27.6 g BOD/(m2 d). Aeration could be an optional strategy for WESISs to achieve high pollutants removal and low CH4, N2O emission when treating wastewater with high SOLR.

Performance of AnMBR in Treatment of Post-consumer Food Waste: Effect of Hydraulic Retention Time and Organic Loading Rate on Biogas Production and Membrane Fouling.

Anaerobic digestion of food waste (FW) is typically limited to large reactors due to high hydraulic retention times (HRTs). Technologies such as anaerobic membrane reactors (AnMBRs) can perform anaerobic digestion at lower HRTs while maintaining high chemical oxygen demand (COD) removal efficiencies. This study evaluated the effect of HRT and organic loading rate (OLR) on the stability and performance of a side-stream AnMBR in treating diluted fresh food waste (FW). The reactor was fed with synthetic FW at an influent concentration of 8.24 (± 0.12) g COD/L. The OLR was increased by reducing the HRT from 20 to 1 d. The AnMBR obtained an overall removal efficiency of >97 and >98% of the influent COD and total suspended solids (TSS), respectively, throughout the course of operation. The biological process was able to convert 76% of the influent COD into biogas with 70% methane content, while the cake layer formed on the membrane gave an additional COD removal of 7%. Total ammoniacal nitrogen (TAN) and total nitrogen (TN) concentrations were found to be higher in the bioreactor than in the influent, and average overall removal efficiencies of 17.3 (± 5) and 61.5 (± 3)% of TAN and TN, respectively, were observed with respect to the bioreactor concentrations after 2 weeks. Total phosphorus (TP) had an average removal efficiency of 40.39 (± 5)% with respect to the influent. Membrane fouling was observed when the HRT was decreased from 7 to 5 d and was alleviated through backwashing. This study suggests that the side-stream AnMBR can be used to successfully reduce the typical HRT of wet anaerobic food waste (solids content 7%) digesters from 20 days to 1 day, while maintaining a high COD removal efficiency and biogas production.

Anaerobic digestion of toluene-laden wastewater under oxygen-deficient mesophilic condition and concurrent retrieval of methane-enriched biogas

Increasing population in the world resulted in the crisis of both water and energy and therefore demanding the treatment of wastewater to make it fit for human use. The present study aims at the degradation of wastewater containing hazardous toluene along with the simultaneous recovery of energy, i.e., biogas which can overcome the crisis of both resources to some extent. For this, anaerobic digestion of toluene with varying concentration was achieved under the mesophilic condition when fed with different amount of substrate level. Examination of the feasible concentration of toluene and glucose (co-substrate) dosage to the reactor was performed in order to evaluate the performance of the anaerobic reactor. During the experiment, toluene degradation and chemical oxygen demand (COD) removal were examined periodically, and the efficiency of degradation was compared with the varying amount of glucose (0.5, 1, and 2 g/L). The high COD removal efficiency (77%) and methane (CH4) production (298 μL) was achieved after degrading 200 mg/L toluene sample when the reactor is fed with 1 g/L of glucose. Thus, 1 g/L was found to be the optimal amount of substrate level suitable for degradation and the efficiency is decreased if the amount of glucose is increased or decreased from this optimal amount. Furthermore, the scanning electron microscopy studies revealed the highly porous nature of sludge fed with 1 g/L glucose than others. Moreover, energy-dispersive x-ray analysis of sludges indicates the presence of different elemental components (carbon, oxygen, silicon, calcium) that confirmed the presence of microbial secretions involved in degradation.

Treatability of household waste plastic garbage bag recycling industry wastewater with membrane

In this study, household waste plastic garbage bag recycling industry wastewater was treated by a membrane process to recycle water for using in the bags washing process. Two different ultrafiltration (UP150 and UP005) and nanofiltration (NF270 and NF90) membranes were tested. The steady-state permeate flux was obtained 14.9 and 19.2 L/m2.h at 5 bar for UP150 and UP005 membranes, respectively. However, the steady-state permeate flux was 12.9 and 8.9 L/m2.h at 20 bar for NF270 and NF90 membranes, respectively. The chemical oxygen demand (COD) was also tested for all membrane permeates and the highest COD removal efficiency was obtained for NF90 membrane. Thus, optimization was carried out using NF90 membrane and the effect of transmembrane pressure (10, 20, 30 bar) and solution pH (5, 7, 9) on COD removal efficiency was tested. The results showed that the highest steady-state permeate flux (23.5 L/m2.h) and COD removal efficiency (95.1%) were obtained at 30 bar and pH 9. After the optimization of the membrane type and operating conditions, 75% recovery was obtained to re-use in the bags washing process. The concentrate stream was treated by an activated sludge process to manage membrane concentrate and to provide discharge standards. The maximum COD removal efficiency in biological treatment for membrane concentrate stream was 96.2% under steady-state condition using a sequencing batch reactor (SBR) operated at 10 days of sludge retention time and 12 h of hydraulic retention time. The proposed combined process including membrane and activated sludge processes was successfully used to recover wastewater.

Effect of different concentrations of substrate in microbial fuel cells toward bioenergy recovery and simultaneous wastewater treatment

ABSTRACT Microbial fuel cells (MFCS) is a promising and expanding technology able to eliminate various pollutants of wastewater while converting its chemical energy into power energy using biocatalysts. The potential application of double-chamber microbial fuel cell (DC-MFC) for chemical oxygen demand (COD) removal and generated power from wastewater in the different conditions is investigated. DC-MFC is operated with anaerobic sludge as an active biocatalyst in an anode section, an aerobic cathode section and a Nafion117 membrane as a separator. The performance of the bioreactor is determined with different concentrations of chemical oxygen demand (COD) loadings in the MFC process, in terms of COD removal, power generation and columbic efficiencies. The results illustrated that COD removal efficiency increased at the high concentrations of organic matter. So that at COD concentration of 2000.0 mg/L the highest COD removal efficiency (84%) was obtained. But with increasing substrate initial concentration to 10000.0 mg/L the efficiency decreased to 79%. The important outputs of the system like the highest voltage, maximum generated power, current density, and energy efficiency with the 100,000 mg/L COD are 447 mV, 50.7 mW/m2, 570.0 mA/m2, and 18.6%, respectively. The optical density levels increased due to bacterial growth while pH severely decreased in the anode chamber when using high-concentration substrates in the MFC.

Whole Genome Sequencing and Comparative Genomic Analyses of Lysinibacillus pakistanensis LZH-9, a Halotolerant Strain with Excellent COD Removal Capability.

Halotolerant microorganisms are promising in bio-treatment of hypersaline industrial wastewater. Four halotolerant bacteria strains were isolated from wastewater treatment plant, of which a strain LZH-9 could grow in the presence of up to 14% (w/v) NaCl, and it removed 81.9% chemical oxygen demand (COD) at 96 h after optimization. Whole genome sequencing of Lysinibacillus pakistanensis LZH-9 and comparative genomic analysis revealed metabolic versatility of different species of Lysinibacillus, and abundant genes involved in xenobiotics biodegradation, resistance to toxic compound, and salinity were found in all tested species of Lysinibacillus, in which Horizontal Gene Transfer (HGT) contributed to the acquisition of many important properties of Lysinibacillus spp. such as toxic compound resistance and osmotic stress resistance as revealed by phylogenetic analyses. Besides, genome wide positive selection analyses revealed seven genes that contained adaptive mutations in Lysinibacillus spp., most of which were multifunctional. Further expression assessment with Codon Adaption Index (CAI) also reflected the high metabolic rate of L. pakistanensis to digest potential carbon or nitrogen sources in organic contaminants, which was closely linked with efficient COD removal ability of strain LZH-9. The high COD removal efficiency and halotolerance as well as genomic evidences suggested that L. pakistanensis LZH-9 was promising in treating hypersaline industrial wastewater.

Effect of operating parameter on the anaerobic digestion oil palm mesocarp fibre with cattle manure for biogas production

Anaerobic digestion is a complex biological process resulting in the conversion of biodegradable organic matter into biogas and mineralized material. Anaerobic digestion involves the breakdown of biomass by a concerted action of a wide range of microorganisms in the absence of oxygen. The biological pre-treatment was used to reduce the lignocellulose content of substrate. Laboratory experiment was carried out in single stage 10 L bioreactors. The reactors were named R1, to R10 at different mixture conditions with organic loading of 1.62 and 2.11 g VS at HRT of 10 days. The result was stable at the initial stage, within the first 10 days was high and was attributed to the consumption of easily degradable COD. These indicate that there is stable COD removal efficiency for the anaerobic digestion of treated OPMF with CM and seeded with POME. The results showed the level of COD removal efficiency was observed and upon the steady state of the reaction. In this experiment, the results indicate that chemical oxygen demand (COD) reduction in reactor R1 shows the best result of the average removal efficiency value of 37.9 %. Although, ambient temperature was adopted, it still shows a high COD removal efficiency in R1 and may be associated to a more stable reaction. This indicated that pre-treated OPMF produced a better COD removal efficiency than the untreated OPMF. The removal efficiency started with 18 % and continued to increase to 38 %. The removal efficiency became relative stable until day 30 which give the highest percentage removal of 45 % which was achieved with a high OLR (2.11 kg VS L−1 d−1). The reductions continued in the same trend until day 20 and remained stable till the end of the experiment. This indicates that the available microorganisms have been exulted by day 20 and this corresponds to a drop to the rate of biogas production. Operating parameters considered in this study have an influence on the rate of biogas produced during anaerobic digestion. The results show that COD, do influence the rate of biogas production.

The Evaluation of Simultaneous COD and Sulfate Removal at High COD/SO42− Ratio and Haloalkaline Condition

The effects of different electron donors on sulfate reduction at high COD/SO42− and haloalkaline conditions were investigated. For this purpose, the anaerobic submerged membrane reactor, fed with acetate and ethanol as an electron donor, was operated at a salinity of 10 g NaCl/L and a high pH (about 9.5) for 210 days. The bioreactor was inoculated with a mixed haloalkaliphilic culture and was enriched with saline soda from Lake Van, Turkey. The bioreactor’s performance was mainly evaluated with the removal of chemical oxygen demand (COD) and sulfate and changes in microbial community. A significant increase for both COD and sulfate removal was simultaneously achieved in the ethanol-fed bioreactor. The highest removal efficiency of COD and sulfate was about 70% and 80%, respectively, once the ratio of COD/SO42− was 6. The effect of hydraulic retention time on treatment performance of the bioreactor was inconsiderable as a result of the low flux during the whole operation time. There was no biogas production throughout the experiment due to the haloalkaline condition in reactor medium. From DGGE analysis, it was postulated that ethanol usage can cause bacterial abundance and diversity in bioreactor medium with no detection of sulfate-reducing bacteria.

Selection of Suitable Filter Materials for Horizontal Subsurface Flow Constructed Wetland Treating Swine Wastewater

This research aims to assess different filter materials in horizontal subsurface flow constructed wetland (CW) planted with combined Phragmites australis Cav. and Cyperus alternifolius L. for treatment of real swine wastewater at a large pig farm in Vietnam. Four CW models including CW1 (gravel), CW2 (gravel, limestone), CW3 (gravel, limestone, and sand), and CW4 (gravel, limestone, and rice husk) were designed and conducted during 90 days of the experiments. The results showed that the removal efficiencies of chemical oxygen demand (COD), total suspended solids (TSS), nitrogen, and phosphorus from swine waster by the CW3 and CW4 models were higher than those by CW1 and CW2. The highest removal efficiency of COD, NH4+-N, TN, and TP by CW3 was 82 ± 2%, 82 ± 4%, 77 ± 1%, and 82 ± 3%, respectively. The result of this study indicates the capacity of combined gravel, limestone, and sand as suitable substrate filter for swine wastewater treatment.

Evaluation of recycled paper mill effluent digestion in a modified anaerobic hybrid baffled (MAHB) reactor: reactor performance & kinetic studies

Recycled paper mill effluent (RPME) consists of various organic and inorganic compounds. In this study, modified anaerobic hybrid baffled (MAHB) bioreactor has been successfully used to anaerobically digest RPME. The anaerobic digestion was investigated in relation to methane production rate, lignin removal, and chemical oxygen demand (COD) removal, with respect to organic loading rate (OLR) and hydraulic retention time (HRT). The analysis using kinetic study was carried out under mesophilic conditions (37 ± 2 °C) and influent COD concentrations (1000–4000 mg L−1), to prove its practicability towards RPME treatment. First-order kinetic model was used to clarify the behavior of RPME anaerobic digestion under different OLRs (0.14–4.00 g COD L−1 d−1) and HRT (1–7 d). The result shows that the highest COD removal efficiency and methane production rate were recorded to be 98.07% and 2.2223 L CH4 d−1, respectively. This result was further validated by evaluating the biokinetic coefficients (reaction rate constant (k) and maximum biogas production (ym)), which gave values of k = 0.57 d−1 and ym = 0.331 L d−1. This kinetic data concludes that MAHB presented satisfactory performance towards COD removal with relatively high methane production, which can be further utilized as on-site energy supply.

Nanosecond pulse used to enhance the electrocoagulation of municipal wastewater treatment with low specific energy consumption

ABSTRACT This study compares the performance of nanosecond pulse (NSP) and direct current (DC) power supplies for use in a municipal wastewater treatment by electrocoagulation (EC). Four Al plates connected in monopolar-parallel configuration (MP-P) were used as electrodes during the EC process. The maximum chemical oxygen demand (COD) removal efficiency reached 68% and 80% using DC and NSP, respectively. Moreover, NSP treatment reduced approximately 15% of the specific energy consumption (SEC) compared with that by DC at a similar COD removal efficiency of ≈ 68%, which was used as a benchmark value. In addition, when using NSP, the SEC required to increase the COD removal efficiency from 60% to 68% was two to three times less than that when DC was applied. The results suggest that an NSP operating at 10 kHz frequency (f) and 1 µs pulse width (pw) are preferred for obtaining higher COD removal efficiencies at a low SEC. The use of an NSP for EC can enhance the COD removal efficiency and reduce the wastewater treatment SEC. The results presented herein promote the use of EC systems combined with renewable energy sources for reducing the net carbon footprint of wastewater processing.

Anaerobically digested blackwater treatment by simultaneous denitrification and anammox processes: Feeding loading affects reactor performance and microbial community succession.

Source diverted blackwater collected from toilets can be anaerobically digested to recover energy. The anaerobically digested blackwater (ADB) contains high levels of ammonium and low carbon to nitrogen (C/N) ratio. In the present study, ADB was treated by a two-stage nitritation-denitrification/anammox process in an integrated fixed film activated sludge-continuous flow reactor (IFAS-CFR). NH4+-N, NO2--N, total nitrogen (TN), and chemical oxygen demand (COD) removal efficiencies were 80%, 82%, 76%, and 78%, respectively. Anaerobic ammonium oxidation (anammox) and denitrification contributed to 44-48%, and 52-56% of total nitrogen removal, respectively. Both of the protein- and humic acid-like matters were removed during the process. An increase in feed load promoted the sustained growth of anammox bacteria-Candidatus Brocadia in the biofilm, as well as an increase of denitrifiers (Pseudomonas, Thermotonus, Phodanobacter, Caulobacter) in both biofilm and suspended biomass, which remained higher in the suspended biomass than in biofilm. Overall, biofilm had higher nitrogen removal efficiency than suspended biomass, while suspended biomass had a higher COD removal efficiency than biofilm.

Are pharmaceuticals removal and membrane fouling in electromembrane bioreactor affected by current density?

Pharmaceutical active compounds (PhACs) have been detected at significant concentrations in various natural and artificial aquatic environments. In this study, electro membrane bioreactor (eMBR) technology was used to treat simulated municipal wastewater containing widely-used pharmaceuticals namely amoxicillin (AMX), diclofenac (DCF) and carbamazepine (CBZ). The effects of varying current density on the removal of PhACs (AMX, DCF and CBZ) and conventional pollutants (chemical oxygen demand (COD), dissolved organic carbon (DOC), humic substances, ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N) and orthophosphate (PO4-P) species) were examined. High COD and DOC removal efficiencies (~100%) were obtained in all the experimental runs regardless of applied current density. In contrast, enhanced removal efficiencies for AMX, DCF and CBZ were achieved at high current densities. Membrane fouling rate in eMBR with respect to conventional MBR was reduced by 24, 44 and 45% at current densities of 0.3, 0.5 and 1.15 mA/cm2, respectively. The mechanism for pharmaceutical removal in this study proceeded by: (1) charge neutralization between negatively-charged pharmaceutical compounds and positive electro-generated aluminium coagulants to form larger particles and (2) size exclusion by membrane filtration.

Electrochemical degradation of Azo-dye Acid Violet 7 using BDD anode: effect of flow reactor configuration on cell hydrodynamics and dye removal efficiency

The electrochemical oxidation of synthetic textile effluent containing Azo-dye Acid Violet 7 (200 mg L−1) was investigated using planar disk electrodes placed in a one inlet–outlet (I–O) cylindrical reaction chamber. Two different I–O configurations were studied, one parallel and the other perpendicular to the electrodes. Both reactors were equipped with boron-doped diamond (BDD) anodes and titanium cathodes. The effect of cell design on the hydrodynamic characteristics and efficiency of the reactors in terms of colour and chemical oxygen demand (COD) removal was studied. Mass transfer coefficient (Km) values of 1.86 × 10−5 m s−1 and 2.56 × 10−5 m s−1 were obtained for the parallel and perpendicular I–O flow reactors, respectively, using the limiting current technique. The degradation results indicated that the colour elimination was quite efficient regardless of the type of reactor used and that complete colour removal could be reached in less than 80 min at applied current density of 30 mA cm−2 and above. However, higher COD removal efficiency was always achieved in the parallel I–O flow cell compared to perpendicular I–O flow reactor at all of the current densities studied, which can be attributed to the possibility of some stagnation in the lateral regions of the electrodes. These favour a longer contact time between the pollutants and the anode, also favouring its removal. Besides, similar electric energy consumption per g COD removal was observed during the treatment with either reactors; thus demonstrating the suitability of the parallel I–O flow cell for the efficient and economic treatment of textile effluent.

Combination of multi-oxidation process and electrolysis for pretreatment of PCB industry wastewater and recovery of highly-purified copper

Current approach for wastewater treatment in the field of printed circuit board (PCB) is uneconomical and resource-wasting, which has turned into a heavy burden for the enterprise. Therefore, it is highly urgent to develop a cost-efficient and sustainable strategy for the remediation of PCB wastewater. In this work, a multi-oxidation coupled with electrolysis approach was proposed for the decontamination of PCB wastewater and recovery of copper element simultaneously. Based on this multi-oxidation of UV/KMnO4/Na2S2O8/H2O2, the chelate bonds of Cu and organic ligands can be effectively broken to release numerous free Cu2+ ions, and chemical oxygen demand (COD) of PCB wastewater sharply decreased from 32,800 to 1680 mg/L, leading to a high COD removal efficiency of 94.9%. Subsequently, as high as 90.1% of free Cu2+ ions can be easily transformed into high-value Cu element by a simple electrodeposition process. The degradation products in different oxidation systems were identified by the LC–MS/MS. The degradation pathway has also been proposed. The relationships among the recovery efficiency of copper, electrode distance and power consumption were studied. Based on the analysis of techno-economic benefits, the net income of this proposed coupling technology in engineering application reached up to ¥1414800.

Black water collected from the septic tank treated with a living machine system: HRT effect and microbial community structure

In this study, the performance of a living machine (LM) system was evaluated for use in the treatment of black water collected from septic tanks with hydraulic retention times (HRTs) of 6, 5, and 4 days. We found that the HRT had little effect on the removal efficiency of chemical oxygen demand (COD). However, the removal rates of total nitrogen (TN) and ammonium nitrogen (NH4+-N) decreased with the reduction of HRT, whereas the removal efficiency of total phosphate (TP) was consistently low because of the long sludge retention time. The working conditions of #1 achieved the highest removal efficiency of COD (85%), NH4+-N (75%), and TN (47%), although the removal efficiency of TP (11%) was slightly lower than that of #2 (12%). The microbial communities in each tank of the LM system were characterized by high-throughput sequencing, which showed that the LM system successfully created more favorable conditions for fermentative bacteria than traditional systems, with relative abundances of 13% (#1), 13% (#2), and 15% (#3) compared to that of the anaerobic/anoxic/oxic (A2O) system (<3%). Smithella was the dominant fermentative bacteria, accounting for 9% (#1), 7% (#2), and 10% (#3) of total bacteria in the LM system. The relative abundances of ammonia oxidizing bacteria (AOB) (12%) and anaerobic ammonium oxidizing bacteria (AnAOB) (7%) in the LM system were much higher than that in the A2O system. Overall, the LM system offered a more sustainable and economical solution for treating black water.

Fe Oxides Loaded on Carbon Cloth by Hydrothermal Process as an Effective and Reusable Heterogenous Fenton Catalyst

Iron based heterogeneous Fenton catalysts are attracting much attention for its economic and environmental friendly characteristics. In this study, iron oxides loaded carbon cloth (assigned as Fe@CC) was prepared using hydrothermal hydrolysis of Fe(NO3)3. The specific surface area of Fe@CC determined by N2 adsorption–desorption Brunauer–Emmett–Teller method was up to 1325.5 m2/g, which increased by 81.8% compared with that of native carbon cloth mainly due to the loading of iron oxide. XPS (X-ray photoelectron spectroscopy) spectra confirmed that the iron oxide on the carbon surface included mainly FeOOH. Its heterogeneous Fenton-like activity was determined using Acid Red G as a model substrate for degradation. Fe@CC maintained high and relatively stable activity during 11 tests, and it showed high COD (Chemical Oxygen Demand) removal efficiency and high apparent H2O2 utilization efficiency. The homogeneous Fenton reaction using the amount of leached Fe(III) suggested that the surficial reaction on Fe@CC was dominant. The stability and the mechanism for gradual decrease of activity during the first 4 tests were also discussed.