Environmental Technology

Cao, Hailin; Liu, Haitao; Ma, Wenchao

doi: 10.1080/09593330.2026.2615169pmid: 41544651

Municipal solid waste incineration (MSWI) fly ash is a hazardous waste, and traditional landfill disposal lacks sustainability. Resource utilization offers a viable pathway for its future management. Heavy metals are key hazardous components in fly ash, and their stabilization is essential for resource utilization. However, traditional high-temperature treatments are energy-intensive and costly, limiting large-scale application. This study proposed an energy-efficient, medium-temperature treatment method for fly ash and evaluated its environmental risks. Molecular dynamics simulations were conducted to elucidate the underlying mechanisms of heavy metal stabilization. The study revealed that co-sintering fly ash with clay at 750°C and 950°C led to a significant reduction in heavy metal leachability, with Pb and Zn concentrations decreasing by 97.4% and 61.7%, respectively. The sintered products developed new fibrous mineral phases, predominantly wollastonite and rankinite, within which heavy metal ions were incorporated through isomorphic substitution for Ca2+ in the crystal lattice, leading to stable immobilization. Sequential extraction analysis showed that the chemical forms of heavy metals shifted from acid-soluble to more stable reducible and oxidizable fractions after treatment. Consequently, the environmental risk levels of Zn and Pb decreased from moderate to negligible, while that of Cd was reduced from high to negligible. Long-term leaching tests under simulated acid rain conditions confirmed that the sintered products maintain high stability during prolonged environmental exposure.

Zeng, Lingcong; Cheng, Yuanyuan; Cheng, Xianxiong; Li, Shaoqin; Wang, Liujia; Long, Chen; Long, Bei

doi: 10.1080/09593330.2026.2616437pmid: 41572667

This study addressed the issue of elevated ammonia nitrogen pollution in wastewater from ionic rare earth mining operations. Given the high costs and limited efficiency of conventional biological denitrification methods, the sulphur-based autotrophic denitrification (SAD) process was explored as a cost-effective alternative to improve nitrogen removal performance. A sequencing batch reactor was operated over 70 days to cultivate and maintain granular sludge, successfully enriching sulphur-oxidising bacteria (SOB). During this cultivation phase, the average sludge particle size increased from 228.69 μm to 709.95 μm, the granulation rate reached 84.56%, and the relative abundance of the SOB genus Thiobacillus rose to 13.57%. An orthogonal experimental design was employed to optimise the operational parameters of the SAD granular sludge. Single-factor experiments were first conducted to assess the effects of sodium bicarbonate concentration (0–2000 mg/L), sludge concentration (3500–6000 mg/L), reaction duration (2–12 h), and sodium sulfide concentration (0–300 mg/L) on the removal efficiencies of total inorganic nitrogen (TIN). The results indicated that sodium bicarbonate concentration was the most influential factor. Subsequently, an L₉(3⁴) orthogonal experiment was designed to determine the optimal operational conditions: 1600 mg/L sodium bicarbonate, 5000 mg/L sludge concentration, 8 h of reaction time, and 37.5 mg/L sodium sulphide. Under these optimised conditions, the TIN removal efficiency reached 67.64%. Economic analysis demonstrated that the unit denitrification cost of the SAD process was 31.83% lower than that of the heterotrophic denitrification process, highlighting its potential as a low-carbon and efficient solution for treating rare earth mining wastewater.

Zhou, Zhiwei; Li, Qing; Sun, Yuanyi; Gu, Xue; Zhu, Huanyi; Li, Yongmei; Shang, Kai; Hu, Xia; Yang, Aijiang

doi: 10.1080/09593330.2026.2618838pmid: 41604514

The production of municipal sludge is increasing rapidly, and the disposal of large amounts of sludge has become a significant challenge in urban development. This study investigates the mechanism and effect of the dewatering pretreatment of municipal sludge using boron-doped diamond (BDD) electrodes. Orthogonal experiments were designed to determine the optimal current density, temperature, pH, and reaction time, using sludge specific resistance (SSR) as the evaluation index. Under these optimal conditions, the BDD electrode disrupted extracellular polymers, cell walls, and cell membranes of sludge microorganisms, as quantified by Coomassie Brilliant Blue-G250 and anthrone colorimetric methods, alongside UV spectrophotometry. Low-field nuclear magnetic resonance (LF-NMR) T2 patterns revealed the transformation of interstitial water in the sludge to free water. Free radical masking experiments and Fourier transform infrared spectroscopy (FTIR) indicated that the presence of ·OH radicals significantly reduced hydrophilic functional groups (-OH, N-H, C-O, -COOH, and -C-O-C-) in extracellular polymeric substances (EPS), thereby reducing hydrophilicity and enhancing dewatering capacity. These findings demonstrate that BDD electrode treatment significantly enhances sludge dewaterability by generating ·OH radicals, which disrupt cellular structures and attack hydrophilic functional groups in EPS, consequently converting bound water into free water.

Abubakari, Sa-Ad; Abuzenah, Hebah; Musa, Musa M.; Abdur Razzak, Shaikh; Alshammari, Salem; Saleh, Salah; Ayirala, Subhash; Salhi, Billel; Nzila, Alexis

doi: 10.1080/09593330.2026.2620606pmid: 41631938

The oil and gas industries generate large-volumes of produced water (PW), a by-product characterized by high salinity, hydrocarbons, and heavy metals. Desalination reduces salinity, but desalinated produced water (DPW) still contains considerable organic pollutants, restricting its reuse, particularly in agriculture. This study aimed to chemically characterize DPW and isolate bacterial strains capable of degrading its organic components. Chemical analysis revealed significantly reduced salinity (0.1% w/v NaCl), low concentrations of nitrate, phosphate, sulfate, and negligible heavy metals. However, total organic carbon (TOC) remained high (∼200 ppm or 200 mg L⁻¹), exceeding permissible limits for agricultural reuse. Gas chromatography – mass spectrometry identified sulfur-containing heterocyclic compounds as the dominant pollutants, along with in inorganic sulfur species. To enable bioremediation, bacterial strains were isolated from oil-contaminated soils using enrichment cultures with DPW as the sole carbon source. Two gram-negative strains, belonging to the species Pseudomonas fluorescens, were identified through 16S rRNA sequencing. Both thrived on glucose, acetate, and dibenzothiophene, a model sulfur-heterocycle. Bacterial growth and TOC removal were further evaluated in media with varying DPW and Bushnell-Hass (BH) ratios. Optimal growth and degradation occurred when DPW was supplemented with BH medium, highlighting the necessity of nutrient addition (biostimulation) to sustain biodegradation. Future work should determine the minimal nutrient supplementation required for efficient degradation while ensuring residual nutrient concentrations remain environmentally acceptable. Additionally, the process must be scaled from batch experiments to continuous bioreactor systems to assess long-term feasibility and scalability.

Luo, Yingli; Liu, Shukai; Wang, Tao; Niu, Xiaoyin; Yin, Xianwei; Liu, Aiju; Ma, Yanfei

doi: 10.1080/09593330.2026.2620607pmid: 41604517

Research on microalgae for wastewater treatment is extensive, and numerous emerging nanomaterials demonstrate excellent pollutant removal capabilities. However, the synergistic effects of combining these approaches for remediating black-odorous water have not been extensively studied. This study integrated titanate nanotubes (TNTs) with Chlorella vulgaris andScenedesmus quadricauda to treat artificially simulated black-odorous water. The growth, physiological status of the microalgae, and pollutant removal efficiencies were analyzed. Results indicate that TNTs(tested at 5–50 mg/L) enhanced the growth of Chlorella vulgarisbut inhibited Scenedesmus quadricauda. The synergistic action of TNTs and microalgae significantly improved the removal efficiencies of NH₄⁺-N and TN. Specifically, the C. vulgaris + TNTs system increased the removal of NH₄⁺-N and TN by approximately 15.9%and 17.2%, respectively, at optimal concentrations, while the S. quadricauda + TNTs system achieved removal rates exceeding 98% for both pollutants, representing more pronounced enhancements. Raman spectroscopy analysis revealed that TNTs promoted theproduction of photosynthetic pigments and proteins in microalgae. The observed synergy primarily stems from the combined roles of TNTs in adsorbing pollutants and stimulating microalgal metabolic assimilation. Furthermore, microbial community analysis indicated distinct differences between the control and TNT-treated groups, with TNTs inhibiting Deinococcus and Pseudomonas while promoting Flavobacterium and Porphyrobacter. It should be noted that this study employed simulated wastewater, which may not fully replicate the complexity of actual black-odorous water bodies. This study provides novel insights and data supporting new strategies for black-odorous water remediation.

Li, Shuai; Zhang, Sha; Li, Dong; Zeng, Huiping; Yuan, Yixing; Zhang, Jie

doi: 10.1080/09593330.2026.2621362pmid: 41631932

The purpose of this study was to investigate the effects of COD interference on biological nutrient removal, granule characteristics, and microbial community dynamics in continuous-flow Simultaneous Nitrification, Denitrification, and phosphorus Removal (SNDPR) granular sludge under low aeration energy consumption conditions. The experiment employed an innovative Automatic Internal Circulation Continuous Flow Reactor (AIC-CFR) at an aeration rate of 0.8 L/min, maintaining the dissolved oxygen level below 0.5 mg/L, and the COD concentration increased from 300 to 500 mg/L in steps of 100 mg/L. The results demonstrated that increasing the COD concentration to 400 mg/L significantly enhanced the removal efficiencies of total phosphorus and total nitrogen, while simultaneously optimizing the settling properties of the granules. However, when the COD concentration reached 500 mg/L, the settling ability and stability of the granules deteriorated. As the COD concentration increased, the population of the filamentous archaea Methanothrix significantly increased, whereas the abundance of the filamentous bacteria Thiothrix gradually decreased. The abundance of these filamentous microorganisms was closely correlated with the sludge volume index, granular integrity coefficient, and extracellular polymeric substances. High-throughput sequencing results revealed that DPAOs-Pseudomonas have consistently been the absolute dominant genus in the system. It is AOA rather than AOB that undertakes the task of oxidizing ammonia nitrogen to nitrous nitrogen. Finally, a granular ecological conceptual model is proposed to elucidate the underlying mechanisms of the AIC-CFR system. This study elucidated the stability mechanism of SNDPR granules, providing technical support for the low-carbon engineering operation of granular sludge.

Ye, Miaomiao; Yang, Tingting; Song, Lei; Xie, Yawei; Fang, Fubing; Liu, Xiaowei

doi: 10.1080/09593330.2026.2622107pmid: 41631937

Peroxymonocarbonate (PMC), a green in situ oxidant formed from the reaction between hydrogen peroxide (H2O2) and bicarbonate (HCO3⁻), has demonstrated promising potential for the degradation of organic pollutants, although its underlying mechanisms remain not fully elucidated. In this study, the degradation efficiency and mechanistic pathways of PMC toward tetracycline (TC) were systematically investigated. Compared to H2O2 alone, PMC exhibited significantly enhanced TC degradation, with a first-order rate constant (k) of 0.0181 min⁻¹, approximately 10 times higher than that of H2O2 alone. Key factors affecting the degradation efficiency, such as anions, cations, pH, humic acid, and different water matrices, were thoroughly examined. Electron paramagnetic resonance (EPR) analysis confirmed the generation of free radicals, while non-radical oxidation pathways were also suggested. Among the reactive oxygen species, ·OH and CO3·⁻ are the primary species driving TC degradation, while ¹O2 and ·O2⁻ act as secondary contributors. Three potential degradation pathways were proposed based on liquid chromatography-mass spectrometry (LC-MS) analysis and density functional theory (DFT) calculations, and the corresponding toxicity predicted using ecological structure-activity relationship (ECOSAR) model. This study provides new insights into the application of environmentally benign oxidants for antibiotic removal and highlights the potential of PMC in water treatment practices.

Jia, Ji; Yin, Sijie; Yin, Xiangbiao; Feng, Wendong

doi: 10.1080/09593330.2026.2624707pmid: 41662166

A two-stage process for the treatment of solid radioactive spent cation exchange resin was developed in this study. The Fenton process was first employed to dissolve solid resin, followed by the O3/Fenton-like process for degrading the resulting organic liquid. The impacts of reaction time, initial pH, concentration, and H2O2 dosage on degradation efficiency were systematically evaluated. Under optimal conditions, a mineralization efficiency exceeding 99.85% was achieved. Initial pH was identified as the most significant factor influencing degradation performance. The reaction followed a pseudo-first-order model based on kinetic fitting. These findings provide foundational data to support the industrial application of the two-stage process for treating radioactive spent cation exchange resin

Chu, Chin-Pang; Yu, Guan-Neng; Kuo, Wen-Chien; Liang, Chih-Ming; Hsieh, Ping-Heng

doi: 10.1080/09593330.2026.2626000pmid: 41662160

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.

Guo, Haiyan; Guan, Dianyong; Bi, Weixuan; Yang, Jiaxing; Liu, Pengzhan; Ren, Kerui

doi: 10.1080/09593330.2026.2626001pmid: 41796047

This study employed a single-stage aerobic sequencing batch reactor (SBR) to establish a simultaneous short-cut nitrification-denitrification (SSND) system, addressing the denitrification challenges in wastewater with low carbon-to-nitrogen (C/N) ratios. By controlling low dissolved oxygen (DO, 0.3–0.5 mg/L) and employing a strategy of gradually increasing influent nitrogen loading, short-cut nitrification was rapidly initiated within 18 days, achieving a nitrite accumulation rate exceeding 95%. Under conditions of an influent C/N ratio of 2, chemical oxygen demand (COD) of 1000 mg/L, and total nitrogen (TN) of 500 mg/L, the single-stage aerobic (O) mode demonstrated superior denitrification efficiency compared to the A/O mode, achieving COD and TN removal rates of 84.2% and 68.9%, respectively. Microbial community analysis revealed successful directed succession of functional bacterial communities: ammonium-oxidizing bacteria (Nitrosomonas) were effectively enriched (abundance increased to 11.10%), while nitrite-oxidizing bacteria (Nitrospira) were effectively suppressed (abundance <0.1%); Functional denitrifying bacteria (Thauera genus) emerged as the dominant genus (30.58% abundance). These bacteria undergo a ‘saturation-starvation’ cycle, utilising intracellular poly-β-hydroxybutyrate (PHB) accumulated during the anaerobic phase as an endogenous electron donor to drive simultaneous denitrification during the aerobic phase. Additionally, the study revealed that under carbon-limited conditions (C/N = 1), environmentally induced autolysis and extracellular polymer secretion occur, explaining fluctuations in effluent COD. This research provides theoretical support for applying the SSND process to treat low C/N wastewater.