Environmental Technology最新文献

The preparation of activated carbon derived from municipal sludge and amino modification for CO₂ adsorption can not only achieve the resource utilization of sludge but also address the issue of CO₂ emission reduction. Municipal sludge was used in this study as a raw material to prepare CO₂ adsorbents via pyrolysis, activation, and amino modification. Microstructural characterization and CO₂ performance tests were conducted to analyze the influence of different activation agents, pyrolysis temperature, and pyrolysis time on the microstructural evolution and CO₂ adsorption performance of sludge-based activated carbon. The results indicate that the solid NaOH activator enabled the sludge to generate more pore structures. When the pyrolysis temperature was 600°C and the pyrolysis time was 60 min, an excellent pore structure was obtained. Nevertheless, an excessively high pyrolysis temperature and time would cause sintering of the samples, leading to pore collapse. Under the aforementioned preparation conditions, the sludge-activated carbon reached its maximum CO₂ adsorption capacity, with the maximum adsorption capacity of CO₂ being 1.369 mmol/g. The adsorption temperature had a significant influence on the final adsorption effect, and the optimal adsorption temperature is 25°C.

Aqueous contamination by arsenic and antimony has become a significant concern due to its prevalence in smelting activities. Nowadays, adsorption stands out as an effective method for the removal of these heavy metal ions from water, particularly when the goal is to achieve high levels of purification and ensure safety. However, the complex nature of smelting wastewater often leads to a decrease in the selectivity and salt resistance of adsorbents under industrial conditions. In this study, we introduce a novel designated composite-resin material (KYE003), which is tailored for the deep purification of arsenic and antimony. By precisely adjusting the synthesis ratios, we have controlled the intrinsic kinetics of material synthesis, enabling the in-situ loading of ferric oxide onto the resin surface, coupled with organic functional groups (-COOH and -SH). The resin's inherent porous structure not only promotes the nucleation and growth of amorphous iron oxide but also establishes a quantitative basis for nano-scale binding sites. Further surface characterisation analysis indicates that interfacial functional groups, including (-COOH, -SH, and -OH), are instrumental in the complexation of arsenic and antimony. The synergistic interactions, such as -O-As/Sb, -COO-As/Sb, and -S-As/Sb, demonstrate that the hybridisation of these groups restructures the interfacial electronic state, thereby enhancing the adsorption performance. The KYE003 material exhibits exceptional adsorptive selectivity and chemical stability under complex conditions, capable of maintaining arsenic concentrations in the effluent below 20 µg·L^-1 until the bed volumes ratio surpasses 6240. This research presents a new perspective for the deep purification of heavy metal ions.

Vermicomposting has been proven to be effective in combating tetracycline resistance genes (TRGs) in organic waste, such as animal manure and sewage sludge. However, the influences of tetracycline resistant bacteria (TRB) in organic waste during earthworm conversions on the fate of TRGs remain poorly understood. Hence, we prepared diets treated with either sensitive or insensitive tetracycline resistant bacteriome (STRB or ITRB) to earthworm midgut fluid and investigated the fate of bacterial communities and TRGs (including tetB, tetC, tetZ, tetL, and tetX) and their response to tetracycline during earthworm conversions in a controllable environment. Results showed that the bacterial composition of casts was highly complex, yet diet-derived bacteria were either minimal or undetectable. Notably, TRGs abundance in casts was dramatically higher than that in diets, indicating that the earthworm gut is a hotspot for TRGs dissemination. Furthermore, the increase in TRGs abundance was more pronounced in casts treated with ITRB compared to those treated with STRB, and this increase was suppressed by tetracycline exposure in casts treated with ITRB. This phenomenon may be due to the fact that diet-derived TRB and/or tetracycline alter the microbial community (e.g. relative abundance of Aeromonas). In conclusion, this study highlights the diet-derived TRB amplify the hotspot effect of earthworm gut on tetracycline-resistance gene dissemination, but regulated by tetracycline.

This study aimed to evaluate the bioleaching of copper from discarded printed circuit boards (PCBs) using the fungus Aspergillus tubingensis UCP 1208 as a sustainable and environmentally friendly alternative for the recovery of valuable metals. The methodology included the acclimatization of the fungus to different concentrations of crushed PCBs, followed by bioleaching assays and copper removal analysis through scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) and inductively coupled plasma optical emission spectrometry (ICP-OES). SEM-EDS analyses revealed significant changes in the morphology and elemental composition of the PCBs after treatment, confirming the efficiency of copper solubilization. Quantitative results indicated that A. tubingensis, acclimatized with 1% (w/v) of crushed PCBs, removed 494.2 mg L⁻¹ of copper for a PCB load of 1 g L⁻¹, representing a 335.5% increase in removal compared to conventional acid digestion. These results demonstrate that bioleaching with A. tubingensis is a viable, efficient, and sustainable approach for the recovery of metals from electronic waste, offering a cleaner alternative to traditional chemical methods by avoiding the use of aggressive acids and contributing to circular economic practices.

For the biological treatment of swine wastewater, accelerating the degradation of COD usually leads to increased microbial nitrification, resulting in a conflict between pollutant removal and nitrogen recycling. In this study, the addition of hematite-biochar mixture and the nitrification inhibitor dicyandiamide (DCD) was proposed and applied to simultaneously enhance COD removal and nitrogen recycling efficiency in a Myriophyllum aquaticum-based swine wastewater treatment process. The results showed that addition of hematite-biochar mixture achieved a 1 times increase on COD removal rate. Meanwhile, the addition of DCD effectively suppressed microbial nitrification but slightly increased nitrogen removal by enhancing nitrogen utilization with Myriophyllum aquaticum. Eventually, the addition of hematite-biochar and DCD simultaneously improved the COD removal and nitrogen recycling rate to 96.9% (vs. 46.6% for control) and 72.8% (vs. 39.9% for control), respectively. Furthermore, microbial community analysis indicated that the developed strategy enhanced the abundance of Firmicutes and the genus Comamonas (strengthening COD removal), while reducing the abundance of nitrifying bacteria (phylum Proteobacteria) (repressing the nitrification process). This work provided a practical approach to accelerate pollutants removal while preserving nitrogen for plant utilization, which would be a promising solution for nitrogen recycling from swine wastewater.

Microalgae are considered promising for wastewater treatment and nutrients recovery. However, microalgae from wastewater usually have a high ash content, which significantly influences on the utilization efficiency of microalgae. In this study, poultry wastewater with different salinity levels was used to cultivate Chlorella sp. in bench-scale ponds. The ion content of the microalgal ash was tested to determine the composition of the ash. The results show that microalgae cultivated in wastewater with higher salinity results in a high ash content, and the ash content of microalgae from fertilizer wasterwater (FW) has a positive linear relationship with the initial salinity of FW. The ash content of microalgae in wastewater with 3.59 g L^-1 salinity is 12.5% higher than that in wastewater with 1.50 g L^-1 salinity. The main compounds of microalgal ash from FW runs were CaO, P₂O₅, MgO, SiO₂, and K₂O (over 5%). The highest removal rates of NH₄⁺-N, TP, and TOC in the FW runs were 99.1%, 93.7%, and 80%, respectively. Except for FW-16, the lipid and protein contents of microalgae from FW runs showed a positive relationship with the dilution ratios. This research aims to propose a way to reduce the microalgae ash when coupling microalgae cultivation with the wastewater.

Silicon-based solar photovoltaic (PV) panels are the most widely deployed technology for renewable electricity generation. However, after their 25-30 year service life, large volumes of end-of-life (EoL) panels accumulate, creating significant waste management challenges. Conventional recycling methods are energy-intensive and economically unattractive, leading to landfilling as the most common disposal route. This practice raises environmental concerns due to the potential leaching of toxic metals such as lead (Pb) and zinc (Zn). In this study, we propose a sustainable recycling strategy that incorporates EoL PV panels into concrete production. Aluminium frames and junction boxes were first removed from the panels, and the remaining laminates were shredded and sieved into three size fractions. The intermediate fraction was used as sand replacement in concrete. Heavy metal leaching was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP), while the environmental impacts of landfill disposal and this recycling approach were compared using Life Cycle Assessment (LCA). TCLP results showed that Pb and Zn concentrations in this concrete were below detectable limits, whereas 3.21 mg/L of Pb and 7.34 mg/L of Zn leached from crushed laminates. LCA results indicated that landfilling imposed high environmental burdens, particularly in marine ecotoxicity (5.36E + 05 kg 1,4-DCB) and global warming potential (2.86E + 03 kg CO₂ eq.), while concrete recycling achieved reductions across all 18 impact categories, including a 69.8% decrease in non-carcinogenic human toxicity. These findings demonstrate that incorporating solar waste in concrete effectively immobilizes hazardous metals and offers a sustainable, low-impact recycling route for PV waste, significantly outperforming landfill disposal.

Batch tests and continuous operation were conducted to evaluate the acute and chronic responses of nitrifying culture under moxifloxacin exposure. The results showed that nitrifying culture exhibited limited capacity for adsorption and biodegradation of moxifloxacin. Ammonium and nitrite oxidation were inhibited by 10 mg/L moxifloxacin within 4 h, reducing nitrite oxidation efficiency by 10%. However, the ammonium oxidation rate gradually recovered to pre-exposure level and developed tolerance during long-term exposure, while the nitrite oxidation rate failed to recover even after the recovery period. Further studies revealed that the inhibition of nitrification was driven by increased reactive oxygen species and decreased activities of ammonium monooxygenase and nitrite oxidoreductase. The absolute and relative abundances of the predominant genus Nitrosomonas continuously increased during exposure, suggesting that moxifloxacin had no adverse effect on the growth of ammonium-oxidising bacteria.

This study aimed to evaluate the effectiveness of mobile organic biofilm (MOB) technology for removing ammonia (NH₃/NH₄⁺, referred to as NH₄⁺) from wastewater in low solids retention time (SRT) and low operating temperature conditions. The MOB technology is based on process intensification using a plant-based media (milled kenaf) to develop a mobile organic biofilm. In the MOB process, media is added to the aeration tanks of an activated sludge process. Two bench-scale sequencing batch reactors (SBRs) with 1.5 L volume were used to assess MOB technology, a control, and a MOB-added reactor, hereafter the MOB reactor. The NH₄⁺ concentration in the influent ranged from 5.5 to 14.9 mg N/L, with an average of 10.1 mg N/L over the study period. The COD level varied from 66.0 to 94.0 mg/L, with an average of 78.8 mg/L. The results showed that the MOB process effectively removes NH₄⁺ and COD with a three-day SRT at 12 °C. The MOB reactor achieved an average of 93.1% NH₄⁺ and over 47% COD removal throughout the stable operation period. MOB represents a promising wastewater treatment technology for the removal of nitrogen in activated sludge facilities.

Extracellular polymeric substances (EPS) play a vital role in forming microbial aggregates such as biofilms, flocs, and granules. However, standardised methods for extracting EPS from the activated sludge across different wastewater treatment processes remain elusive. The anaerobic-anoxic-oxic (A²O) process, widely used in wastewater treatment, was selected to investigate EPS extraction from its activated sludge. This study compared twenty-five physicochemical methods for EPS extraction from the activated sludge collected from the secondary sedimentation basin of an A²O reactor, evaluating EPS yield, composition, and cell lysis. The results show that combined chemical-physical extraction methods, particularly NaOH/heat treatment, achieved higher extraction rates while preserving EPS characteristics. This method yielded higher concentrations of proteins (PN) and polysaccharides (PS) with reduced cell lysis compared to other techniques. In most methods, protein content exceeded polysaccharides content, with PN/PS ratios ranging from 0.005 to 4.17 g/g. Higher PN/PS ratios were associated with smoother, more uniform EPS morphology. Particle size distribution of the treated sludge showed minimal variation between methods. Fourier transform infrared (FTIR) and excitation emission matrix (EEM) fluorescence spectroscopy confirmed the presence of proteins, polysaccharides, and DNA in EPS, with NaOH/heat treatment more effectively preserving functional groups. Optimisation tests identified 45 min as the ideal heating duration for maximum EPS extraction. Overall, this study provides a systematic evaluation of EPS extraction methods from the activated sludge in A²O systems, offering methodological insights for future wastewater treatment research.