ABSTRACT Aerobic biodegradation of mixed phenolic wastewater containing phenol and catechol was investigated under thermophilic conditions to integrate biodegradation kinetics with practical sequencing batch reactor (SBR) design. A thermotolerant microbial consortium was used to evaluate treatment performance, parameter optimization, substrate inhibition kinetics, and reactor-scale translation. Six physicochemical parameters – temperature, pH, incubation time, medium volume, inoculum size, and initial substrate concentration – were optimized to maximize removal efficiency. Under optimal conditions (45 °C, pH 8.5, 48 h, 600 mL working volume, 12% inoculum, and 1000 mg L⁻¹ total substrate), 99.9% degradation of the phenol–catechol mixture was achieved within 48 h. The biodegradation kinetics followed the Haldane substrate inhibition model, yielding kinetic parameters of μm = 0.061 h⁻¹, Ks = 38.65 mg L−1, Ki = 138.24 mg L−1, and Yx/s = 0.0035 OD600·L·mg−1, with strong model agreement (R2 > 0.99). Using these parameters, a pilot-scale SBR (2.2 m³ working volume) was designed with a 48 h reaction cycle, aeration rate of 1 vvm, and power input of 0.05 W L−1, achieving 95–98% substrate removal per cycle under thermophilic and alkaline conditions. Overall, this study demonstrates the direct integration of mixed-substrate biodegradation kinetics with reactor-scale process design, bridging laboratory-scale modelling and applied wastewater treatment engineering for high-strength phenolic effluents.

ABSTRACT Nonsteroidal anti-inflammatory drugs (NSAID) are the most frequently observed micropollutants in the effluents of conventional wastewater treatment plants and hybrid technologies could be an alternative to conventional systems. However, the effect on micropollutants’ removal has not been well studied. In this study, the impact of hybrid systems on micropollutant removal, as well as the determination of the dominant microbial communities, were investigated. For this purpose, laboratory-scale control hybrid and micropollutant-amended (1 μg/L of diclofenac, ketoprofen, indomethacin, and mefenamic acid, 10 μg/L of ibuprofen, and naproxen) hybrid reactors were operated at organic loading rate of 0.3 kg COD/m3.day and ammonium concentration of 60 mg/L N with a sludge retention time of 10 days and hydraulic retention time of 24 hrs. Effluent chemical oxygen demand (COD) was below 30 mg/L in the control and micropollutant hybrid reactors. Significant removal efficiencies for ibuprofen (99.7%), indomethacin (99.0%), naproxen (97.6%), mefenamic acid (97%), and ketoprofen (91.4) were achieved. Results revealed that NSAIDs did not have a chronic inhibitory effect on the biodegradation of organic matter and nitrification process. Higher biodiversity observed in attached biomass of micropollutant hybrid reactor might contribute to enhance system stability and performance. Dominant genera detected in hybrid micropollutant reactor were Chitinophagaceae (10.1%), Ferruginibacter (7.8%), and Comamonas (6.8%) for suspended biomass, and Fimbriimonadaceae (8.7%), Parafilimonas (6.5%), and Rickettsia (5.6%) for attached biomass, which might contribute to the removal of NSAIDs. Moreover, the genera Chitinophagaceae and Comamonas which are reported as heterotrophic ammonia-oxidizing bacteria, might contribute to nitrification in hybrid biofilm reactors.

ABSTRACT The integration of semiconductor nanomaterials with electroactive bacteria offers a promising strategy for enhancing light-driven biohybrid systems. However, the generation of reactive oxygen species (ROS) during photocatalysis poses a significant challenge, impairing microbial viability and reducing process efficiency. In this study, we developed a novel biohybrid system by sequentially biosynthesizing cadmium sulphide (CdS) nanoparticles and manganese oxide (Mn3O4) nanozyme on the surface of Shewanella oneidensis MR-1, creating an S. oneidensis-CdS@Mn3O4 composite. The CdS nanoparticles facilitated efficient light absorption and electron transfer, significantly enhancing hydrogen production under visible light irradiation. However, ROS accumulation (·OH, O2⁻·, and H2O2) induced oxidative stress, reducing bacterial viability and metabolic activity. To address this, Mn3O4 nanozyme were introduced, demonstrating robust ROS-scavenging capabilities, reducing hydrogen peroxide (H2O2) levels by 66.7%, superoxide radical (O2⁻·) by 60.7%, and hydroxyl radical (·OH) by a significant margin. As a consequence, hydrogen production by S. oneidensis-CdS@Mn3O4 reached 1203.60 µmol g-dcw⁻¹ after 70 h of visible-light irradiation, which was 2.6-fold higher than that of S. oneidensis-CdS. Furthermore, Mn3O4 preserved cell viability, maintained higher NADH/NAD⁺ ratios, and enhanced ATP levels, indicating improved metabolic efficiency. Structural characterization via scanning electron microscopy (SEM) energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) confirmed the successful synthesis of CdS and Mn3O4 on bacterial surfaces, while photoelectrochemical analysis verified retained photosensitivity. This study presents a simple yet effective strategy for mitigating ROS-induced damage in bio-semiconductor systems, offering insights into the design of more stable and efficient biohybrid platforms for sustainable energy production. Key points A biohybrid system (S. oneidensis-CdS@Mn3O4) was constructed by sequential biosynthesis of CdS and Mn3O4 nanozyme. Mn3O4 efficiently scavenged ROS, increasing hydrogen production by 2.6-fold compared to S. oneidensis-CdS.

ABSTRACT Polyethylene (PE) waste is one of the major ecological problems because of its recalcitrant nature for environmental degradation. Despite the conventional methods of plastic waste management, biological approaches are gaining particular attention as a sustainable alternative for its management. Recent research has shown several indigenous microbes capable of degrading different types of polyethylene. Herein, we isolated and identified the bacterium, Rhodococcus pyridinivorans, which has shown the capability to degrade with UV pre-treated low-density polyethylene (LDPE). A systematic study was conducted for 130 days to highlight the association of R. pyridinivorans with LDPE and its ability to cause morphological and weight loss changes in the polyethylene. The changes on bacterial treated PE surfaces were observed with scanning electron microscopy and atomic force microscopy analysis. The potential of R. pyridinivorans to cause surface changes is also confirmed with 18% reduction and 15% increment in carbon and oxygen content, respectively. Further, R. pyridinivorans treatment induces hydroxyl and carbonyl groups, which results in an overall reduction in hydrophobicity of PE sheets. Overall, these findings demonstrate that R. pyridinivorans can associate with polyethylene for its survival. Bioinformatic analysis revealed a conserved domain (PF00487) in alkane monooxygenase, potentially involved in LDPE surface changes. In future, the genomic and proteomic analysis of R. pyridinivorans may provide a better understanding of the molecular mechanism of PE degradation that could be employed as an alternative strategy for removing polyethylene waste from the environment.

ABSTRACT Multi-metal carbonates (MMCs) containing Mn2+, Fe2+, Ca2+, and Mg2+ were synthesised via a Na2CO3-assisted co-precipitation process at 50°C under mildly alkaline pH (∼9.5) conditions. Na2CO3 acted as both the carbonate source and a mild pH buffer, facilitating the formation of complex carbonate and hydroxide phases. Structural analysis (XRD, FTIR, and XPS) revealed that MMCs are composites of single and binary carbonates, layered double hydroxides (LDHs), and hydromagnesite. Upon CO2 exposure, selective dissolution of CaMn(CO3)2 and hydromagnesite occurred without reprecipitation of CaCO3 or MgCO3 phases due to acidic pH (<6), leading to the enrichment of MnCO3 and M2+Fe3+-LDHs. This transformation was accompanied by a mesostructural reorganisation, as evidenced by an increase in specific surface area from 29.3 to 46.3 m2/g and a reduction in system pH. These results provide fundamental insights into phase-selective transformations induced by CO2 interaction with MMCs synthesised under mildly alkaline carbonate precipitation conditions, thereby clarifying the underlying transformation pathways and mesostructural evolution.

ABSTRACT Chitosan is a promising coagulant for bacteria, viruses and turbidity in water, but needs identification of optimal dose–polymer combinations. This research tested chitosans to identify dose range and characteristics that provide highest simultaneous reduction of bacteria, viruses, and turbidity, and possible coagulation mechanisms, including charge neutralization, sweep coagulation, and electrostatic patch. Three molecular weights (MW) and degrees of deacetylation (DD) were tested at doses 1, 3, 10 and 30 mg/L using jar tests in water containing clays, E. coli, and bacteriophage MS2. Turbidity removal was 93–99% at 1 and 3 mg/L, with no significant difference between MW. MW, DD and dose significantly affected viral and bacterial reduction. Across doses, MW 100,000 Da had highest mean log10 MS2 (3.5) and E. coli (3.5) reductions. The 100,000 Da/10 mg combination had the highest mean log10 E. coli (4.5) and MS2 (3.5) reductions simultaneously. Overall, 100,000 Da/3 mg and 1,000,000 Da/3 mg maximize reduction of turbidity and MS2, but not E. coli. 100,000 Da/10 mg maximized E. coli reduction and gave MS2 reductions similar to 100,000 Da/3 mg, but turbidity reduction was lower. Chitosan reduced turbidity, bacteria, and viruses in water, influenced by MW, DD, and dose. Data suggests that there is no single dose/MW/DD combination that produced significantly higher reductions of all three contaminants simultaneously but good removal of all three can be achieved with 100,000 Da at 3 or 10 mg/L. Chitosans can be effective coagulant-flocculants in water at reasonably achievable doses using polymer characteristics that are commercially available.

ABSTRACT The widespread incineration of municipal solid waste (MSW) has raised concerns regarding environmental pollution caused by the hazardous heavy metal lead (Pb) in fly ash (FA), necessitating safe treatment prior to landfill disposal. This study developed a novel organic chelating agent-TA (The chelating agent is named as an acronym derived from the two primary monomers), a trithiocyanuric acid-functionalized allylthiourea macromolecule, and evaluated its effectiveness in stabilising Pb in municipal solid waste incineration fly ash (MSWI-FA). Compared to conventional organic chelating agents such as dithiocarbamates (DTC), TA presents an environmentally superior alternative by eliminating the use of highly volatile and hazardous CS2 (Carbon disulfide) as a raw material. The addition of 4 wt% (Weight Percentage) TA successfully reduced the leaching concentration of Pb from fly ash to a level below the Chinese landfill regulatory limit. This reduction was primarily attributed to the stabilisation treatment significantly decreasing the acid-extractable fraction of Pb from 12.845% to 3.79%. Furthermore, the TA treatment also facilitated the reduction of Pb (IV) to the more stable Pb2+, contributing to the overall enhanced stability and reduced environmental risk. HIGHLIGHTS A novel macromolecular chelator (TA) was synthesised from trithiocyanuric acid and allylthiourea for lead(Pb) stabilisation. TA achieves efficient Pb immobilisation, reducing leaching concentration to 0.22 mg/L, meeting Chinese landfill standards. The stabilisation mechanism involves the reduction of Pb (IV) to Pb2+ and the formation of a tetrahedral structure through chelation of lead by TA, as evidenced by XAFS and XPS analysis. TA converts acid-extractable Pb into stable oxidisable and residual fractions, significantly lowering environmental risk.

ABSTRACT This study evaluated the thermophilic anaerobic co-digestion of primary and secondary pulp and paper sludge through BMP assays and pilot-scale CSTR operation. Primary sludge exhibited a methane potential of 381 m³ CH₄/ton VS, 2.5 times higher than secondary sludge (149 m³ CH₄/ton VS). Co-digestion at a 3:1 TS ratio yielded 332 m³ CH₄/ton VSfed under thermophilic conditions – substantially higher than mesophilic operation. Pilot-scale thermophilic digestion achieved stable performance with 51.3% TCOD, 29.1% SS, and 52.5% VSS removal, alongside a methane yield of 333 m³ CH₄/ton VSfed. Transitioning from a two-phase to a single-phase configuration eliminated foaming and improved operational robustness. High CaCO₃-derived alkalinity ensured strong buffering, though it slightly reduced methane concentration. The system offered an energy recovery potential of 15,716 kWh/day and 2,834 tons CO₂-eq/year reduction. Although short-term stability was maintained, the COD:N:P ratio (∼400:10:1) suggests phosphorus may limit long-term performance.

ABSTRACT As the wetland ecosystem is a potential sink of plastics pieces, the photodegradation of microplastics could be boosted by iron(hydr) oxides, which considered as the Fenton or Fenton-like reactions induced. However, the pathways and internal mechanisms by which iron(hydr) oxides enhanced the ultraviolet degradation of plastics in the wetlands remain unclear. Therefore, the degradation of polystyrene (PS) and polyvinyl chloride (PVC) under ultraviolet light (365 nm) was studied in the UV Fenton and simulated micro wetlands. Results showed that UV irradiation caused notable changes in the surface morphology of plastics. Fenton reaction led to more significant, and generated oxygen-containing functional groups such as C = O. The weight loss rate of PS reached 28.3 ± 6.64%, while PVC reached 35.6 ± 1.52%, significantly surpassing the individual conditions of UV light at 20.3 ± 1.66% and 20.98 ± 8.48%, respectively. The mechanism of •OH in the process of plastic degradation was elucidated, while analysis of the degradation products was conducted. The potential risks for the UV degradation of PS and PVC were explored in constructed wetlands by detecting the changes of microbes. After preliminary aging, microbial activity associated with the degradation of polycyclic aromatic hydrocarbon compounds produced during plastic degradation is enhanced. Therefore, there may exist microbial communities in wetland ecosystems that are capable of degrading plastic. This study supported a hypothesis that the goethite/haematite Microcosm Constructed Wetlands (MCWs) would be efficiency for the degradation of plastic. It would be proved further and the organic carbon releasing during the plastic degradation should also be focused on.

ABSTRACT Nowadays, the presence of triazine-based azo dyes like Reactive Red 120 (RR 120) in textile wastewater poses a significant hazardous environmental impact, deteriorating the aquatic biota and requiring an effective treatment method. Compared to conventional energy-intensive and secondary waste-generating physicochemical methods, biological methods, especially microbial biodegradation, offer a sustainable, eco-friendly, and cost-effective alternative for the treatment of effluents containing dye-laden wastewater. This study evaluated the efficacy of Bacillus tequilensis MCC2908 for biodegradation and detoxification of RR 120 using a continuously Packed Bed Bioreactor (PBBR). The experimental findings revealed an optimum range of ILR within 75–85 mg/L.day, achieving 94.2 ± 2.71% RE and 24.1 ± 1.205 mg/L.day EC, avoiding limitations imposed by mass transfer and bioreaction, and maintaining a robust and efficient bioreactor system. Crystal Violet staining test confirmed the quantitative assessment of biofilm growth, while SEM images made it observable on the polyurethane bio-carrier. The FTIR spectra confirmed the biodegradation of RR 120, showing significant changes in the functional groups. The detoxification was demonstrated using bacterial and phytotoxicity, validating the toxicity reduction, further duly supported by photosynthetic pigment analysis. The Monod model and the Andrew-Haldane kinetics significantly described microbial growth under non-inhibitory and inhibitory conditions, respectively. Nevertheless, the present findings not only highlighted the potential of biofilm-based PBBR but also delivered an eco-friendly, sustainable solution for the remediation of textile wastewater. Future studies may explore the scaling up of this biotechnological solution for the mitigation of industrial challenges and establish hybrid approaches to further enhance biodegradation efficiency. Highlights PBBR significantly achieved efficient biodegradation and detoxification of RR 120. An optimum ILR of 75–85 mg/L.day exhibited the best operating conditions for PBBR. Microbial biomass and biofilm formation were quantified using the Crystal Violet Staining method. Phytotoxicity, photosynthetic pigment analysis, and bacterial toxicity unveiled the RR 120 detoxification. Moderate Ki and low Ks values depicted the resilience and high microbial activity for RR 120.