Environmental Technology最新文献

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.

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.

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.

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.

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.

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.

Phenolic compounds are hazardous industrial pollutants due to their acute environmental toxicity. This study investigates the degradation of 4-chlorophenol (4-CP) using an Ozone Plasma Nanobubble Reactor (OPNR) under varying gas flow rates (1-5 L/min), voltages (10 and 17 kV), and initial 4-CP concentrations (50 and 250 mg/L). The results showed that at an initial 4-CP of 50 mg L^-1 and oxygen flow rate of 4L min^-1, the process at voltages of 5, 10, and 17 kV for 30 minutes resulted in 4-CP degradation of 33.96, 100, and 99.98% respectively. The process using oxygen generated higher 4-CP degradation percentage values (up to 100%) than that using free air input (up to 89.01%). The process at a voltage of 17 kV and various oxygen gas flow rates of 1, 2, 3, 4, and 5 L min^-1 for 60 minutes resulted in 4-CP degradation of 99.80, 99.90, 99.93, 100, and 99.66% at an initial 4-CP of 50 mg L^-1 and then 89.01, 99.60, 99.84, 98.91, and 99.55% at an initial 4-CP of 250 mg L^-1. Therefore, the highest 4-CP degradation using oxygen input by using a voltage of 17 kV for 60 minutes with initial concentrations of 50 mg L^-1 and 250 mg L^-1 was 100% (using oxygen flow rate of 4L min^-1) and 99.60% (using oxygen flow rate of 2L min^-1), respectively. It shows that the OPNR reactor can work optimally.

The substances in ecosystems flow along the food chain. Therefore, we should establish a monitoring system for antibiotic resistance genes (ARGs) in fertilizer products as soon as possible to regulate the use of fertilizers. In this study, three groups of cattle manure organic fertilizers were set up according to the ratio of straw addition, namely CK: cattle manure: straw = 6:4; M1: cattle manure = 100%; M2: cattle manure: straw = 8:2. All groups were supplemented with microbial agents. Their effects on ARGs, class 1 integron integrase genes (intI1) and bacterial communities were investigated. At the end of composting, the relative abundance of sul1, sul2, tetG, and intI1 in M1 and M2 were significantly lower than that in the CK group, and most of the ARGs in each group were removed. The changes in the relative abundance of ARGs are related to changes in microbial community structure. The establishment of temperature conditions is a key factor affecting the structure of microbial communities. Bacillus may play an important role in controlling the relative abundance of ARGs. We found that the most suitable ratio of cattle manure to straw was 8:2 among the three groups, which not only ensured the balanced nutritional composition of organic fertilizers, but also effectively reduced the abundance of ARGs.

Potassium ferrate (K₂FeO₄) has been widely applied as a pretreatment agent for residual sludge digestion, but the complete synthesis of its solid form is costly. In this study, the use of ferrate anode solution (FAS) was examined as a more economical alternative. FAS is generated as an intermediate byproduct during the electrolytic production of solid K₂FeO₄. The performance of FAS was compared with that of conventional solid K₂FeO₄ to assess their respective effects on anaerobic acid production and sludge dewatering. The results indicate that sludge soluble chemical oxygen demand (SCOD) was increased to 3807 mg/L at the low dosage of 10 mL/L, and the production of short-chain fatty acids (SCFAs) reached 2142 mg COD/L. At this dosage, higher efficiencies in protein and polysaccharide release were achieved compared with high-dose K₂FeO₄ (0.5 g/g TSS). Sludge settling and dewatering properties were also improved, and reductions of 9.1% in sedimentation ratio and 9.7% in cake moisture content were achieved during pretreatment. These findings suggest that FAS, as an intermediate byproduct, can replace solid K₂FeO₄ for sludge pretreatment because of its high efficiency at low dosages and its distinct enhancement of dewatering performance. FAS may therefore serve as a more economical and effective option.

In this study, we investigated the impact of applied current, charge loading, initial pH, EC time, and packed-bed reactor density on total arsenic removal from groundwater (GW) in a scrap iron-based batch electrocoagulation (EC) process. The best operating conditions to achieve over 93% total arsenic removal for GW₁ and GW₂ were identified as follows: i = 50 mA, q = 1.25 C/L (7.77 F/m³), pH = 7.6, m_b = 40 g Fe/L, and t_EC = 10 min for GW₁; and i = 100 mA, q = 5.0 C/L (3.1 F/m³), pH = 7.1, m_b = 40 g Fe/L, and t_EC = 25 min for GW₂. GW treated with the EC process shows that arsenic does not pose a risk to humans and does not increase the likelihood of cancer, as demonstrated by chronic daily intake (CDI), hazard quotient (HQ), and carcinogenic risk (CR) analyses. The sludge produced after the EC process was examined using Scanning Electron Microscopy (SEM), which revealed a dense and porous structure. Energy Dispersive X-ray (EDX) analysis confirmed effective treatment, as evidenced by the accumulation of arsenic and iron. Furthermore, a comprehensive evaluation was conducted to assess the arsenic removal capacity, energy consumption, total operating costs, and kinetic analysis. The results show that the EC reactor using scrap iron is a reliable approach for treating GW contaminated with arsenic.