Biodegradability Of Wastewater Research Articles

Optimized approach for naphthalene wastewater biodegradation by Enterobacter ludwigii NS12 isolated from petroleum industry sludge: Bioreactor study and kinetic investigation

Polycyclic aromatic hydrocarbons (PAHs) pollution is a pressing concern in environments, primarily due to human activities. Limited research exists on the degradation of PAHs by indigenous bacterial strains compared to other degraders. This study focuses on naphthalene biodegradation by isolated bacterial strains from petroleum waste. Naphthalene poses significant threats to ecosystems, inducing genotoxic, mutagenic, and carcinogenic effects. Bioremediation offers a safe and cost-effective solution by employing microbes to degrade naphthalene into non-toxic by-products. In this study, Enterobacter ludwigii NS12 found as the most efficient strain for naphthalene biodegradation. In the subsequent investigation the effect of key process parameters, including pH and temperature, on the biodegradation of naphthalene were studied. Under optimal conditions (pH 7.0 and temperature of 30 °C), Enterobacter ludwigii NS12 exhibited an 89.2 % removal efficiency in the bioreactor for naphthalene wastewater at a concentration of 300 mg/L. The confirmations of naphthalene biodegradation were investigated through residual analysis, revealing dibutyl phthalate and 1-octanol, 2-butyl as metabolites. Additionally, growth kinetic parameters μmax and Ks were evaluated, resulting in values of 0.2380 per day and 158.57 mg/L for Enterobacter ludwigii NS12, respectively. The findings of this study hold significant promise for the bioremediation of naphthalene contamination in the environment.

EFFECT OF DAIRY AND MEAT WASTEWATER IRRIGATION ON SEEDLING GROWTH

Milk and meat processing industries release large quantities of nutrient-rich wastewater with organic compounds (proteins, fats, carbohydrates) in high concentrations. Reusing and recycling this biodegradable wastewater for crop irrigation could be a sustainable solution once the phytotoxic effects of wastewater on crops have been investigated. Therefore, the aim of this study was to evaluate the effects of milk and meat processing wastewaters on germination percentage, seed vigour indices, the seedling tolerance index and the phytotoxicity index of pea (Pisum sativum L.), sugar maize (Zea mays saccharata), purslane (Portulaca oleracea), wheat (Triticum aestivum) and red spinach (Amaranthus dubius). The two wastewater types were collected at the inlet of the city’s sewage system and analysed to determine their physicochemical and microbiological characteristics. The seeds of all five plant species were irrigated with untreated wastewater effluents. The highest - germination percentages were obtained for wheat (92%) and the lowest for red spinach (2.5%). Wheat, purslane, pea and red spinach samples irrigated with meat processing wastewater had higher germination percentages than samples irrigated with dairy wastewater. A higher phytotoxicity was observed for sugar maize, followed by red spinach irrigated with both types of wastewater. Future investigation into the effects of effluent dilution on these types of plants is recommended.

Potential of hospital wastewater treatment using locally isolated Chlorella sp. LH2 from cocoon wastewater

Chlorella sp. is able to grow and transform inorganic and organic contaminants in wastewater to create biomass. In the present study, Chlorella sp. LH2 isolated from cocoon wastewater was able to thrive in hospital wastewater, then remove nutrients and eliminate E. coli ATCC 8739. The results indicated that optimal cultivation conditions of Chlorella sp. LH2 in hospital wastewater were pH of 8, light:dark cycle of 16:8 at 30oC. The inhibitory effect of chlorination on algae growth was accompanied with the chlorine concentration. BOD5:COD ratio of 0.77 indicated biodegradability of hospital wastewater. The untreated and treated wastewatee samples were collected to investigated the nutrient removal efficiency after 10 days. Untreated and treated results were192 ± 8.62 mg/l 23.91 ± 2.19 mg/l for BOD5; 245 ± 9.15 mg/l and 47.31 ± 5.71 mg/l for COD. The treated value met the required standards for hospital wastewater treatment. The removal efficiency total nitrogen and total phosphorus were 68.64% and 64.44% after 10 days, respectively. Elimination of E. coli ATCC 8739 after 7 days by Chlorella sp. LH2 was 88.92%. The results of this study suggest the nutrients and pathogens removal potential of Chlorella sp. LH2 in hospital wastewater for further practical applications.

Techno-economic comparison of two hydroxyl and sulfate radicals based advanced oxidation process for enhancing biodegradability of pulp and paper mill wastewater

The aim of this study is to provide an Advanced Oxidation Process (AOP) based solution to enhance biological treatment efficiency by improving biodegradability of wastewater. Photo-Fenton and Peroxydisulfate (PDS)/UV processes were selected in this study as a representative of hydroxyl and sulfate radical based AOPs. A central composition design (CCD) employed to optimize operational cost and BOD/COD ratio to determine optimal conditions for enhancing wastewater treatment efficiency. The study achieved a maximum COD removal of 71.5 % and increased wastewater biodegradability. Optimal conditions for Photo-Fenton process were DOD (H2O2) 0.28, [Fe2+] 106.26 mg/L, and pH 2.32, costing 2.27 USD per 1 kg COD removed. For PDS/UV process, 75.5 % COD removal was achieved at a cost of 10.6 USD/1 kg removed COD. The PDS/UV process had higher COD removal than Photo-Fenton but did not improve wastewater biodegradability. Optimal conditions were DOD (PDS) 0.19, pH 6.68, costing 10.6 USD/1 kg COD removed.

Enhanced mitigation of acidic and basic dyes by ZnO based nano-photocatalysis: current applications and future perspectives.

Dye wastewater possess immense toxicity with carcinogenic properties and they persist in environment owing to their stability and resistance to chemical and photochemical changes. The bio degradability of dye-contaminated wastewater is low due to its complex molecular structure. Nano-photocatalysts based on zinc oxide are reported as one of the effective metal oxides for dye remediation due to their photostability, enhanced UV and visible absorption capabilities in an affordable manner. An electron-hole pair forms when electrons in the valence band of ZnO nano-photocatalyst transfer into the conduction band by absorbing UV light. The review article presents a detailed review on ZnO applications for treating acidic and basic dyes along with the dye degradation performance based on operating conditions and photocatalytic kinetic models. Several acidic and basic dyes have been shown to degrade efficiently using ZnO and its nanocomposites. Higher removal percentages for crystal violet was reported at pH 12 by ZnO/Graphene oxide catalyst under 400nm UV light, whereas acidic dye Rhodamine B at a pH of 5.8 was degraded to 100% by pristine ZnO. The mechanism of action of ZnO nanocatalysts in degrading the dye contamination are reported and the research gaps to make these agents in environmental remediation on real time operations are discussed.

Sequential Treatment by Ozonation and Biodegradation of Pulp and Paper Industry Wastewater to Eliminate Organic Contaminants.

In this research, the decomposition of toxic organics from pulp and paper mill effluent by the sequential application of ozonation and biodegradation was studied. Ozonation, as a pre-treatment, was executed to transform the initial pollutants into less toxic compounds (such as organic acids of low molecular weights). Biodegradation was executed during three days with acclimated microorganisms that were able to complete the decomposition of the initial organic mixture (raw wastewater) and to achieve a higher degree of mineralization (85-90%). Experiments were performed under three different conditions: (a) only ozonation of the initial contaminants, (b) only biodegradation of residual water without previous treatment by ozone and (c) ozonation followed by biodegradation performed by acclimated microorganisms. In the case of 72 h of biodegradation, the mineralization efficiency reached 85% and 89% after 30 and 60 min of ozonation, respectively. The no significant difference in this parameter coincided with the calculated generalized microorganisms' consortia specific growing rate μmax that was reduced from 2.08 × 10-3 h-1 to 6.05 × 10-4 h-1 when the ozonation time was longer. The identification of the organics composition by gas chromatography with mass detector (GC-MS) before and after treatments confirmed that the proposed combined process served as a more efficient alternative to secondary and tertiary treatments (mineralization degree between 60 and 80% in average) of the paper industry wastewater.

Pretreatment of hypersaline and high-organic wastewater with a three-dimensional electrocatalytic system: a pilot-scale study.

The three-dimensional electrocatalytic oxidation (3DEO) is a promising electrochemical system in the treatment of refractory wastewater, but still far from large-scale applications. In this work, we prepared 146.5 Kg Ti-Sn-Sb@γ-Al2O3 particle electrodes to construct a 3DEO system for the pretreatment of hypersaline and high-organic wastewater in an industrial park sewage plant, with activated carbon particle electrodes as a comparison. The average COD removal rates of Ti-Sn-Sb@γ-Al2O3 and activated carbon-based 3DEO systems were 24.43 and 48.73%, respectively, and the energy consumption of the two 3DEO systems were 102.8 and 31.4 kWh/Kg COD, respectively. However, compared to the negligible enhancement of wastewater biodegradability in the activated carbon 3DEO system, the Ti-Sn-Sb@γ-Al2O3 3DEO system greatly improved the biochemical index (B/C) from 0.021 to 0.166 (by 690.5%). Due to its superior catalytic capacity, Ti-Sn-Sb@γ-Al2O3 outperforms activated carbon in improving biodegradability as the latter relies mainly on adsorption. The results of this work provide a 3DEO engineering practice experience on the pretreatment of hypersaline and high-organic wastewater.

Effect and mechanism of iron-carbon micro-electrolysis pretreatment of organic peroxide production wastewater.

The wastewater from organic peroxide production has high chemical oxygen demand (COD) concentration and poor biodegradability, so it is necessary to find a cost-effective treatment method. The iron-carbon microelectrolysis (IC-ME) technology was used to pretreat the organic peroxide production wastewater, and the influence of reaction conditions on the removal effect of pollutants and the degradation mechanism were studied. The effects of initial pH, iron filings, iron-carbon ratio, and reaction time on the wastewater treatment were investigated by single-factor and response surface optimization experiments, and the degradation mechanism was analyzed by three-dimensional fluorescence spectroscopy, UV-Vis, and gas chromatography mass spectrometry (GC-MS). The experimental results showed that the COD removal efficiency was 35.67% and the biodegradability of wastewater was increased from 0.113 to 0.173 under the conditions of initial pH of 3.1, the dosage of iron filings of 30.5g/L, the ratio of iron-carbon of 1.01, and the reaction time of 122.8min, and the process of IC-ME for degrading COD of wastewater from the production of organic peroxide was consistent with the secondary reaction. The IC-ME process could decompose macromolecular organic compounds such as tyrosine proteins and aromatic proteins, and improve the biodegradability of wastewater. It provides a theoretical reference for the practical application of IC-ME to treat this type of wastewater.

Biodegradation of olive mill wastewater by two bacterial strains

Wastewater from olive mill is a by-product of olive oil production, that is a serious environmental problem in many Mediterranean countries. The production of large quantities of waste in a short period of time together with the high organic load and high toxicity of the waste make it difficult to deal with the problem. Phenolic compounds are one of the main factors responsible for the toxicity of olive mill wastewater (OMW). In the present work, two selectively anaerobic bacteria, Sporolactobacillus spp. and Rhodopseudomonas spp. isolated from compost tea were used. These two strains were tested for their ability to reduce the BOD5 and COD levels and to degrade polyphenols responsible for the toxicity of OMW. The two strains were able to grow on a dilution of a natural OMW and largely degrade the polyphenols. The dilution depended on the initial COD value of the waste. After 90 days of treatment reduction over 70% was observed in all three parameters which were measured while in an additional sampling that carried out in the 150th day, the reduction of BOD5, COD and total phenols concentration, reached to 96.1%, 81.8% and 75.1% respectively. Additionally, an increase in the pH was observed, moving from acidic to slightly alkaline. All these features make the two strains attractive candidates for the development of a biotechnological process for the biodegradation of OMW.

Anodic oxidation of ciprofloxacin antibiotic and real pharmaceutical wastewater with Ti/PbO2 electrocatalyst: Influencing factors and degradation pathways

This study investigated the impact of operational variables including current density, solution pH, sodium sulfate electrolyte concentration, initial pollutant concentration, and reaction time on ciprofloxacin (CIP) anodic oxidation and its COD removal by Ti/PbO2 electrocatalyst. Ti/PbO2 anode was prepared by electrochemical method and its characteristics were determined using SEM, EDX-map, XRD, and linear sweep voltammetry (LSV) techniques. Under optimal conditions, the removal rate of CIP and COD at the initial concentration of 15 mg/L of the pollutant after 75 min of reaction was 92 % and 88.8 %, respectively. CIP mineralization was confirmed by evaluating its UV–vis spectra and cyclic voltammetry (CV) curves during the process. Considering the degradation intermediates identified by LC-MC analysis, the main reactions in CIP mineralization pathways were discussed in detail. Finally, the improvement of biodegradability of pharmaceutical wastewater during anodic oxidation treatment was evaluated. The results indicated that the biodegradability of wastewater significantly increased from BOD/COD = 0.18 for raw wastewater to BOD/COD = 0.42 for treated wastewater. The results showed that anodic oxidation with Ti/PbO2 electrocatalyst can be a practical method of treating wastewater that contains resistant and toxic pharmaceutical compounds.

Enhanced biodegradability and ammonia nitrogen removal of high-salinity pharmaceutical wastewater by ozonation with iron-based monolithic catalyst packing

High-salinity pharmaceutical wastewater has gained much attention due to its refractory organic contaminants which are difficult to be effectively removed by traditional treatment methods, catalytic ozonation as an effective method for advanced treatment is expected to solve this problem. In this research, the treatment efficiency of ozonation with iron (Fe)-based monolithic catalyst packing for high-salinity pharmaceutical wastewater advanced treatment was evaluated, and a combination of catalytic ozonation-anoxic oxic (CO-AO) process has been applied to improve the existing wastewater treatment system. The influence of the ratio of O3 dose to influent COD (O/C) on COD, BOD5/COD, NH4+-N and NO3−-N was systematically investigated by regression analysis. Results showed that Fe-based monolithic catalyst packing could effectively remove COD (163.5 mg/L to 118.2 mg/L on average) and NH4+-N (70.3 % on average) from wastewater and improve the biodegradability of wastewater (the average BOD5/COD increased from 0.065 to 0.165). Regression analysis showed that the biodegradability of high-salinity pharmaceutical wastewater improved with the increase of O/C in the range of 0.1–1.3. The operation data of 588 days showed that the catalytic ozonation-anoxic oxic process could greatly reduce the effluent COD and NH4+-N concentration. The Cl− was the key factor associated with a large amount of NO3−-N in effluent. The long-term deposition of CaCO3 has a negative effect on the treatment effect, but it can improve the corrosion resistance of the catalyst. The findings of this study clearly demonstrate the significant potential and feasibility of Fe-based monolithic catalyst packing, also promote the application of the catalytic ozonation-anoxic oxic in high-salinity actual wastewater treatment.

Expression and characterization of an organic solvent tolerant recombinant lipase from Staphylococcus capitis SH6 for food wastewater treatment

The study illustrated here aims on an organic solvent tolerant lipase from Staphylococcus capitis (SCL). The gene part, encoding the mature lipase, was cloned and sequenced. The concluded polypeptide sequence, equivalent to the protein, consist of 388 amino acid residues with a molecular mass of about 45 kDa. A structure-based alignment of the SCL amino acid sequence shows high identities with those many staphylococcal lipases. From this alignment of sequences, the catalytic triad (Ser 117, Asp 308 and His 347) of SCL could be identified. The mature part of the SCL was expressed in Escherichia coli and the recombinant lipase (r-SCL) was purified to homogeneity. The purified r-SCL presented a quite interesting stability at low temperatures (< 30 °C) and the enzyme was found to be highly stable in polar organic solvent and at a pH ranging from 3 to 12. After that, we have demonstrated that the recombinant enzyme may be implicated in the biodegradability of oily wastewater from effluents of fast-food restaurants; the maximum conversion yield into fatty acids obtained at 30 °C, was 65%.

Study on sewage characteristics in rural China and pollutants removal performance of biologically enhanced internal circulation treatment system

With rapid economic development and urbanization in China, rural wastewater treatment has become an important issue. This study investigated 63 rural sewage treatment stations in northern, central and southern Shaanxi, China for a 1-year period, 2021 to 2022. The main purpose of the research was to investigate the quality and discharge characteristics of rural sewage, along with current problems in rural wastewater treatment, in order to provide evidence for the optimal construction and operation of rural sewage treatment stations. We found that the biodegradability of rural wastewater is adequate, and BOD5/COD ratio in sewage was 0.4, which is suitable for biological treatment. It has obvious intermittent flow cut-off characteristics, and the range of cut-off duration of sewage was 6–16 h/d, which leads to poor pollutant removal efficiency (COD: 50.0 ± 29.2%, NH4+-N: 46.0 ± 26.1%, TN: 38.5 ± 24.9% and TP: 38.3 ± 23.8%) in sewage treatment stations. In response to the above characteristics, the rural sewage biologically enhanced internal circulation treatment (BEICT) system was constructed. After 97 days of operation, the system has a stable removal effect on TN and TP with an average removal rate of 77.42% and 89.69%, respectively, under the condition of influent interruption for 12 h per day. The activated sludge of system maintained good activity and stable sedimentation performance during the whole experiment, with MLVSS/MLSS and SVI of 0.72 and 128 mL/g, respectively. This study can provide the basis and technical support for the accurate design of rural sewage treatment facilities, and has important significance for guiding the treatment of rural domestic sewage in China.

Study on the performance of Anerinibacillus sp. in degrading cyanide wastewater and its metabolic mechanism

Cyanide extraction dominates the gold smelting industry, which leads to the generation of large amounts of cyanide-containing wastewater. In this study, Aneurinibacillus tyrosinisolvens strain named JK-1 was used for cyanide wastewater biodegradation. First, we tested the performance of JK-1 in degrading cyanide under different conditions. Then, we screened metabolic compounds and pathways associated with cyanide degradation by JK-1. Finally, we explored the potential JK-1–mediated cyanide degradation pathway. Our results showed that the optimal pH and temperature for cyanide biodegradation were 7.0 and 30 °C, respectively; under these conditions, a degradation rate of >98% was achieved within 48 h. Untargeted metabolomics results showed that increased cyanide concentration decreased the abundance of metabolic compounds by 71.1% but upregulated 32 metabolic pathways. The Kyoto Encyclopedia of Genes and Genomes enrichment results revealed significant changes in amino acid metabolism pathways during cyanide degradation by JK-1, including cyanoamino acid metabolism, β-alanine metabolism, and glutamate metabolism. Differential metabolic compounds included acetyl-CoA, l-asparagine, l-glutamic acid, l-phenylalanine, and l-glutamine. These results confirmed that cyanide degradation by JK-1 occurs through amino acid assimilation. This study provides new insights into the mechanism of cyanide biodegradation, which can be applied in the treatment of cyanide wastewater or tailings.

Catalytic ozonation of a petrochemical wastewater containing high concentration of dinitrotoluene

Catalytic ozonation of a real industrial wastewater containing recalcitrant nitroaromatic compounds was investigated by different catalysts, and removal of color and COD was tracked over time. The effects of operational parameters such as catalyst type (MnO2, Nano-MnO2, ZnO, SnO2, Fe3O4, nZVI, and diatomite earth), initial pH, ozone dosage, and catalyst dosage on the removal efficiency were studied. Experimental results showed that MnO2 performed significantly better than other catalysts, with Nano-MnO2 resulting in over 80% COD removal, from 21750 to 3915 mg/L. Conventional MnO2 catalyst, on the other hand, resulted in only 66% COD removal. Besides, biodegradability of the recalcitrant initial wastewater improved from 0.29 to 0.88 after 3 h of ozonation. Color removal efficiency was nearly complete (>99%) for both conventional and Nano-MnO2. An analysis of complete degradation using GC–MS indicated that 2,4-DNT and other organics were completely removed; whereas, 2,6-DNT was partially degraded.

Adding iron shavings in activated sludge system to enhance removal of refractory organics and nitrogen for textile-dyeing wastewater

To improve the biodegradability of textile-dyeing wastewater, reduce the biotoxicity of refractory pollutants to activated sludge, and enhance the removal of refractory organics and nitrogen for wastewater. A new coupled system of adding iron shavings in activated sludge was developed for the treatment of textile-dyeing wastewater. The results showed that the average removal efficiencies of chemical oxygen demand and total nitrogen in the coupled system reached 74.9% and 55.0%, respectively. On day 60, the mean granular size and sludge volume index after 30 min of the coupled system reached 206 µm and 24 mL/g, respectively, and aerobic granular sludge was formed. The microbial community structure and function in the system was changed, especially the increase of autotrophic denitrifiers (Hydrogenophaga, Xanthobacter, and Unclassified_f_Comamonadaceae), hydrolytic acidification bacterias (Ottowia and Limnobacter), which enhanced the performance of simultaneous nitrification and denitrification. The monitoring of different periods showed that the specific oxygen uptake rate associated with ammonia oxidation and heterotrophic bacteria in the coupled system was significantly higher than that in the control group, which indicated that iron shavings act as a detoxification function in refractory wastewater. In addition, the iron content of the sludge in the coupled system was 9.6% higher than that of the control group. These iron by-products were good flocculants, and have a significant performance of the adsorption for pollutants. Furthermore, the mechanism of synergistic treatment of wastewater by the coupled system was proposed.

Enhancing biodegradability of refractory insensitive munition preparation wastewater via advanced oxidation treatment: Experimental study and process parameters optimization

Efficient treatment of insensitive munition Butyl-(2-azidoethyl) nitramine (BuAENA) preparation wastewater (BPW) is of utmost importance due to its high concentration of refractory organic compounds and toxic pollutants. The BPW exhibits a CODCr of up to 100 g/L and a low ratio of BOD5 to CODCr (BOD5/CODCr < 0.2), necessitating through degradation of pollutants and enhancement of biodegradability for subsequent biochemical processing. In this study, we propose a novel approach utilizing γ-alumina loaded LaFeO3 perovskite (LFA) to activate peroxymonosulfate (PMS) for BPW degradation, which can effectively degrade refractory organic pollutants in BPW and greatly improve BOD5/CODCr. The degradation mechanism involved various reactive species, including hydroxyl radicals, sulfate radicals, and singlet oxygen, with singlet oxygen being identified as the dominant oxidant responsible for the degradation process. To optimize the degradation process, a 4-factor-3-level Response Surface Methodology (RSM) and Multilayer Perceptron (MLP) artificial neural network (ANN) were employed to model the degradation process of BPW. This study presents a promising approach for the comprehensive treatment of refractory wastewater. By improving the biodegradability of BPW and promoting a more cost-effective operating process, the proposed method holds potential for practical application in the industry of insensitive munition BuAENA preparation wastewater.

Modular design of vegetable polyphenols enables covalent bonding with collagen for eco-leather

Natural renewable materials have been engineered to synthesize functional products because of their wide availability and excellent biodegradability. Particularly, vegetable polyphenols have been regarded as sustainable tanning agents in the leather industry. However, the non-covalent binding nature and high consumption of polyphenols in the leather matrix have limited its potential for replacing chrome tannage. In this work, we developed a series of new polyphenol derivatives by selectively conjugating cyanuric chloride (CC) with phenolic group, and therefore introduced covalent binding moieties in polyphenol for the tanning process. Specifically, polyphenols with different molecular sizes, i.e., tannic acid (TA), ellagic acid (EA), and gallic acid (GA), were modified and evaluated in a comparative study. The obtained triazine-conjugated polyphenol derivatives (i.e., GACC, EACC, and TACC) exhibited appropriate molecular weight (460−1130 Da) and superior stability in the tanning bath (pH ∼8.0), which can effectively penetrate collagen networks. We further investigated the tanning performance of GACC, EACC, TACC, and a commercial triazine tanning agent (i.e., SACC). These polyphenol derivatives exhibited covalent and non-covalent synergistic interaction with collagen, endowing leather with excellent fiber dispersion and overall performance (i.e., thermal stability, organoleptic and physical properties). Of note, the tanning system effectively reduced the dosage of polyphenols and organic carbon emission and improved the biodegradability of wastewater. Together with these outstanding results, we envision that this work will pave the promising way for eco-leather manufacturing.

Treatment of Eucalyptus chemical-mechanical pulp wastewater by coupling system of advanced catalytic oxidation and biodegradation: Synergistic effect of ozonation photocatalytic-microbial

In addressing the issues concerning the challenging treatment, extensive discharge, substantial organic pollution load, and the intricate composition of chemical-mechanical pulp (CMP) wastewater in the pulp and paper industry, an innovative coupled advanced oxidation and biodegradation techniques known as the intimate coupling of ozone oxidation and photocatalysis-biological treatment (ICOPB) was developed for CMP wastewater remediation. The focus of the present research was to explore the optimization of this system, to comprehend the degradation mechanisms, and to understand microbial reaction behavior. Moreover, the study evaluated the degradation efficiency of four potential mechanisms inherent to ICOPB, which include adsorption, photocatalysis, biological treatment, and coupled photocatalytic-biological indirect wastewater treatment. Under the optimal conditions, wherein the O3 concentration was maintained at 35 mg/min, the carrier filling rate was kept at 5 %, pH was held at 7, and aeration was kept at 0.6 L/min, the degradation efficiencies for COD, BOD, and TOC reached 80.7 %, 91.6 %, and 84.6 %, respectively. When compared with the ICOP (intimate coupling of ozone oxidation and photocatalysis) procedure, the ICOPB demonstrates a superior removal efficiency and more comprehensive mineralization. Microbial diversity results indicated that Proteobacteria actively contribute to the subsequent biodegradation of CMP wastewater treated with the ICOPB system. As revealed by the GC–MS analysis and toxicity assessments of intermediate products, ICOPB notably amplified the rate of organic matter degradation and concurrently reduced the toxicity of the effluents. In conclusion, the findings of this research offer an innovative method for the effective degradation of CMP wastewater, thereby addressing a significant environmental concern in the pulp and paper industry.

Coupling the electrocatalytic dechlorination of 2,4-D with electroactive microbial anodes.

This work proves the feasibility of dechlorinating 2,4-D, a customary commercial herbicide, using cathodic electrocatalysis driven by the anodic microbial electrooxidation of sodium acetate. A set of microbial electrochemical systems (MES) were run under two different operating modes, namely microbial fuel cell (MFC) mode, with an external resistance of 120 Ω, or microbial electrolysis cell (MEC) mode, by supplying external voltage (0.6 V) for promoting the (bio)electrochemical reactions taking place. When operating the MES as an MFC, 32% dechlorination was obtained after 72 h of treatment, which was further enhanced by working under MEC mode and achieving a 79% dechlorination. In addition, the biodegradability (expressed as the ratio BOD/COD) of the synthetic polluted wastewater was tested prior and after the MES treatment, which was improved from negative values (corresponding to toxic effluents) up to 0.135 in the MFC and 0.453 in the MEC. Our MES approach proves to be a favourable option from the point of view of energy consumption. Running the system under MFC mode allowed to co-generate energy along the dechlorination process (-0.0120 kWh mol-1 ), even though low removal rates were attained. The energy input under MEC operation was 1.03 kWh mol-1 -a competitive value compared to previous works reported in the literature for (non-biological) electrochemical reactors for 2,4-D electrodechlorination.