Water Science and Technology最新文献

Biogas, consisting mainly of CO₂ and CH₄, offers a sustainable source of energy. However, this gaseous stream has been undervalued in wastewater treatment plants owing to its high CO₂ content. Biogas upgrading by capturing CO₂ broadens its utilisation as a substitute for natural gas. Although biogas upgrading is a widely studied topic, only up to 35% of produced raw biogas is upgraded in the world. To open avenues for development research on biogas upgrading, this paper reviews biogas as a component in global renewable energy production and upgrading technologies focusing on electrochemically driven CO₂ capture systems. Recent progress in electrochemical CO₂ separation including its energy requirement, CO₂ recovery rate, and challenges for upscaling are critically explored. Electrochemical CO₂ separation systems stand out for achieving the most affordable technology among the upgrading systems with a low net energy requirement of 0.25 kWh/kg CO₂. However, its lower CO₂ recovery rate compared to conventional technologies, which leads to high capital expenditure limits the commercialisation of this technology. In the last part of this review, the future perspectives to overcome the challenges associated with electrochemical CO₂ capture are discussed.

This study explores the computational fluid dynamics (CFD) simulation of oxygen (O₂) and hydrogen sulfide (H₂S) mass transfer in a highly turbulent stirring tank. Using the open-source software OpenFOAM, we extended three-dimensional two-phase flow solvers with a rotating mesh feature to model the mass transfer processes between the water and air phases. The accuracy of these simulations was validated against experimental data, demonstrating a strong agreement in the mass transfer rates of H₂S and O₂. The investigation highlights the impact of turbulence on mass transfer coefficients, confirming the reliability of the solvers for predicting mass transfer in turbulent conditions. The results suggest that these CFD models can serve as effective tools for understanding and optimizing sewer system designs. Additionally, the study highlights the potential of numerical simulations to reduce the need for extensive and potentially hazardous laboratory experiments.

Rhodococcus sp. strain p52, an aerobic dioxin degrader, was capable of utilizing petroleum hydrocarbons as the sole sources of carbon and energy for growth. In the present study, the degradation of the mixture of aliphatic hydrocarbons (hexadecane and tetradecane) and aromatic hydrocarbons (phenanthrene and anthracene) by strain p52 was examined. The results showed that the degradation of phenanthrene was enhanced in the presence of hexadecane or tetradecane due to increased bioavailability and improved cell surface hydrophobicity, which facilitated better substrate uptake. Conversely, the degradation of hexadecane and tetradecane decreased in the presence of aromatic hydrocarbons, likely due to the cometabolic effect, metabolic regulation, substrate competition, and the shift in enzyme activity. Moreover, the removal of 4.4 g L^-1 diesel fuel, a complex mixture of aliphatic hydrocarbons and aromatic hydrocarbons, was investigated and 63.7% of oil contents were depleted within 96 h. Therefore, strain p52 showed the potential to remove petroleum pollutants.

Contamination by heavy metals (HMs) in aquatic ecosystems is a worldwide issue. Therefore, a feasible solution is crucial for underdeveloped and developing countries. Waste-derived materials (WDMs) exhibit unique physical and chemical properties that promote diverse mechanisms for the removal of HMs in constructed wetlands (CWs). In this study, we aimed to report the removal efficiency of HMs of vertical-flow constructed wetland (VFCW) systems using different WDMs, such as clinker brick (Jhama), eggshells, and date palm fiber (DPF). Synthetic wastewater with high concentrations (3.3-61.8) mg/L of HMs (As, Cr, Cd, Pb, Fe, Zn, Cu, and Ni) was applied to the systems followed by 3 days of hydraulic retention time. The results demonstrate that removal efficiencies of HMs ranged between 94.8 and 98.7% for DPF, 95.4-98.5% for eggshells, and 79.9-92.9% for the Jhama-filled CWs, while the gravel-based systems were capable of 73-87.6% removal. Two macrophytes, Canna indica and Hymenocallis littoralis were planted in the CWs and exhibited significant accumulation of HMs in their roots. The study reports that WDMs are effective for concentrated HM removal in CWs, and macrophytes demonstrate significant phytoremediation capabilities. The findings of this study will facilitate the economically feasible and efficient design of CWs for effectively treating concentrated HMs in wastewater.

Trenchless pipe renewal can be a more cost-, time- and environmentally effective alternative to traditional open-cut replacement. It reduces service disruptions for surrounding infrastructures and is often cheaper, especially when extensive excavation works are necessary, particularly in cold climates, like Norway, where trenches are traditionally deep due to frost security requirements. Still, the uptake of trenchless technologies is still limited in the Norwegian market. In this study, interviews were conducted with representative actors in the Norwegian water industry (water utilities, contractors, and consultants), with the aim of revealing how the technology for renewal of pipes is selected in the planning phase and identifying hindering and enabling factors for trenchless technology uptake in the market. Factors identified include market conservativism, lack of trust between stakeholders, missing guidelines about the distribution of risk, lack of knowledge/specialization in utilities and consultant offices, and issues pertaining to the project delivery method and tendering process. These factors indicate which measures could be implemented to increase the uptake of trenchless technologies in the Norwegian and similar markets. Suggested measures include strengthening the position of stakeholder independent trade organization, facilitating cooperation between smaller utilities and adapting the tendering process to better reflect the requirements of the projects.

Coal power plants adversely impact air pollution, but they also pose a risk to our water sources. Discharge wastewater from power plants may degrade the quality of nearby water bodies. This study evaluates the potential water-related environmental impacts of electricity generation at an ultra-supercritical coal power plant in Malaysia using the life cycle assessment method. The inventory data were gathered from a Malaysian power plant, and supporting data were taken from the relevant literature. Utilizing the ReCiPe 2016 impact assessment method, this study analyses the mid-point impact categories of freshwater eutrophication (FEP), marine eutrophication (MEP), freshwater ecotoxicity (FETP), and marine ecotoxicity (METP). The results indicate that METP is the leading risk, with an average impact of 1.94 × 10^-2 kg 1,4-DCB per kWh electricity generated, followed by FETP (1.40 × 10^-2 kg 1,4-DCB), FEP (4.66 × 10^-4 kg P eq), and MEP (2.95 × 10^-5 kg N eq). About 95% of the mid-point impact is due to the extraction and processing of hard coal. These findings underscore a critical aspect of environmental management at the supply chain level. Furthermore, mitigating direct emissions from power generation could reduce the mid-point impact, as demonstrated by comparisons with previous research.

The advanced anaerobic technology (AAT), developed based on an immobilized high-rate anaerobic reactor, was applied as a pretreatment of municipal wastewater (WW) at Karmiel's treatment plant in Israel. The demonstration-scale AAT (21 m³) system was operated at a flow rate of 100 m³day^-1 municipal WW mixed with olive mill wastewater (OMW) (0.5 m³day^-1) to simulate the scenario of illegal discharge of agro-industrial WW. The AAT provided a stable performance. Specifically, AAT enabled treating high organic loads (9.3 kg m^-3day^-1) resulting from OMW discharge by shaving the high peaks of organic content and protecting the subsequent activated sludge process. This system enabled the recovery of a significant part of the organic load by anaerobic biodegradation to produce biogas, shown to be highly dependent on temperature and partly on the organic loading rate. The outcomes indicate that the AAT could tolerate an addition of up to 0.5% OMW to municipal WW by removing more than 50% of the total chemical oxygen demand and 18-47% of polyphenols. This work shows that the AAT system has the potential of pretreating municipal WW, increasing the energy efficiency of the plant, and protecting small-medium WWTPs from sudden agro-industrial discharges.

Road runoff underwent treatment using a filter filled with sludge from drinking water treatment plants to assess its capacity for removing dissolved organic matter (DOM). This evaluation utilized resin fractionation, gel permeation chromatography, three-dimensional excitation-emission matrix fluorescence spectroscopy, and UV-Visible spectroscopy. The filter demonstrated enhanced efficiency in removing dissolved organic carbon, achieving removal rates between 70 and 80%. It effectively targeted macromolecular DOM components present in road runoff, with hydrophobic organic compounds showing higher removal rates than hydrophilic ones. Additionally, acidic and neutral organic substances were preferentially removed over basic organic compounds. Fluorescent substances identified in road runoff DOM included fulvic acid-like, humic acids, and protein-like substances, all of which exhibited significantly reduced intensities in fluorescence peaks after filtration. Furthermore, filtration led to a decrease in the aromatization and humification of runoff DOM due to the effective removal of aromatic compounds and macromolecular structural components.

Anaerobic treatment of sulfur-rich wastewater is challenging because sulfide greatly inhibits the activity of anaerobic microorganisms, especially methanogenic archaea. We developed an internal phase-separated reactor (IPSR) that removed sulfide prior to methanogenesis by gas stripping using biogas produced in the reactor. The IPSR was fed with synthetic wastewater containing a very high sulfide concentration of up to 6,000 mg S L^-1 with a chemical oxygen demand (COD) of 30,000 mg L^-1. The IPSR was operated at an organic loading rate of 5-12 kg COD m^-3 day^-1 at 35 °C. The results show that the sulfide concentration was reduced from 6,000 mg S L^-1 in the influent to <700 mg S L^-1 in the first-stage effluent. The second-stage effluent contained <400 mg S L^-1. As a result of effective sulfide removal by its gas stripping function, the IPSR had a COD removal efficiency of >90% over the entire experimental period. High-throughput 16S rRNA gene sequencing revealed that the major anaerobic archaea were Methanobacterium and Methanosaeta, which are frequently found in high-rate anaerobic reactors. Thus, the IPSR maintains these microorganisms and achieves high-process performance even when fed wastewater with very high sulfide concentrations.

Hexafluoropropylene oxide trimer acid (HFPO-TA) is an emerging alternative to traditional perfluoroalkyl substances (PFASs), which is characterized by its biotoxicity and persistence. The UV/sulfite/iodide photo-induced hydrated electrons system can effectively degrade HFPO-TA under mild conditions. However, the effects of water quality on this system need to be urgently investigated. This study explored the impact of common aqueous constituents, such as Cl-, HCO3-, PO43- and humic acid (HA) on the defluorination efficiency of HFPO-TA by the UV/sulfite/iodide system. Results indicated that low concentrations of Cl- (<1.0 mM), PO43- (<0.01 mM), and HA (<1.0 mg/L) have little effect on defluorination efficiency. However, as concentrations increase, these constituents can interact with photosensitizers or reactive species within the system, leading to a decrease in defluorination efficiency. HCO3-, in their various solution states, can compete with HFPO-TA for the hydrated electron (eaq-) or engage directly with the photosensitizer, resulting in a hindrance to the defluorination capabilities of the system. Furthermore, it was identified that the components in Xiaoqing River, especially Cl- and HCO3-, could greatly inhibit the defluorination and degradation efficiency of HFPO-TA by the system. Pretreatment such as nanofiltration would effectively mitigate this problem.