Environmental Fluid Mechanics - Based on the mechanism of landslide dam failure caused by overtopping, a simplified mathematical model for simulating dam breach overtopping flow processes was... 相似文献
Water contamination by emerging organic pollutants is calling for advanced methods of remediation such as iron-activated sulfite-based advanced oxidation. Sulfate radical, SO4??, and hydroxyl radical, ?OH, are the primary reactive intermediates formed in the Fe(III)/sulfite system, yet the possible involvement of Fe(IV) produced from Fe(II) and persulfates is unclear. Here we explored the role of Fe(IV) in the Fe(III)/sulfite system by methyl phenyl sulfoxide (PMSO) probe assay, electron paramagnetic resonance spectra analysis, alcohol scavenging experiment, and kinetic simulation. Results show that PMSO is partially transformed into methyl phenyl sulfone (PMSO2), thus evidencing Fe(IV) formation. The remaining degradation of PMSO is due to SO4?? and ?OH. The contribution of Fe(IV) versus free radicals is progressively promoted when the Fe(III)-sulfite reaction proceeds, with an upper limit of 80–90%. The contribution of Fe(IV) versus free radicals increases with Fe(III) and sulfite dosages, and decreases with increasing pH. Overall, our findings demonstrate the involvement of Fe(IV) in the Fe-catalyzed sulfite auto-oxidation process.
• 23 available research articles on MPs in drinking water treatment are reviewed.• The effects of treatment conditions and MP properties on MP removal are discussed.• DWTPs with more steps generally are more effective in removing MPs.• Smaller MPs (e.g.,<10 μm) are more challenging in drinking water treatment. Microplastics (MPs) have been widely detected in drinking water sources and tap water, raising the concern of the effectiveness of drinking water treatment plants (DWTPs) in protecting the public from exposure to MPs through drinking water. We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment (DWT), including laboratory- and full-scale studies. This article summarizes the major MP compositions (materials, sizes, shapes, and concentrations) in drinking water sources, and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes. The discussed drinking water treatment processes include coagulation-flocculation (CF), membrane filtration, sand filtration, and granular activated carbon (GAC) filtration. Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water. Various influential factors to MP removal are discussed, such as coagulant type and dose, MP material, shape and size, and water quality. It is anticipated that better MP removal can be achieved by optimizing the treatment conditions. Moreover, the article framed the major challenges and future research directions on MPs and nanoplastics (NPs) in DWT. 相似文献
• Municipal solid waste (MSW) was fermented, screened, gasified, then co-processed.• Co-processing MSW in cement kilns could cause excessive pollutant emissions.• Bypass flue gas can be disposed of through the main flue system.• Popular MSW co-processing methods do not affect cement quality. Cement kiln co-processing techniques have been developed in the past 20 years in China, and more than 60 factories now use fermentation, screening, and gasification pre-treatment techniques to co-process municipal solid waste (MSW). There three complete MSW pre-treatment techniques, co-processing procedures, and environmental risk assessments have been described in few publications. In this study, we assessed the effectiveness of each technique. The results suggested that the pollutant content released by each pre-treatment technology was lower than the emission standard. To reveal the mechanisms of pollutant migration and enrichment, the substances in the kiln and kiln products are investigated. The input of co-processing materials (Co-M) produced by fermentation caused formation of polychlorinated dibenzo-p-dioxins and dibenzofuran (PCDD/Fs) in the bypass flue gas (By-gas) in excess of the regulatory standard. The Co-M input produced by the screening and gasifier technologies caused the total organic carbon (TOC) concentration to exceed the standard. In addition, the NOx, TOC, and PCDD/Fs in the By-gas exceeded the regulatory standard. Raw meal was the primary chlorine and heavy metals input stream, and clinker (CK) and cement kiln dust (CKD) accounted for>90% of the total chlorine output stream. Flue gas and CKD were the primary volatile heavy metal (Hg) output streams. Greater than 70% of the semi-volatile heavy metals (Cd, Pb, Tl and Se) distributed in hot raw meal and bypass cement kiln dust. The low-volatility heavy metals were concentrated in the CK. These results indicated that co-processing techniques used in China still require improvement. 相似文献
• Retrofitting from CAS to MBR increased effluent quality and environmental benefits.• Retrofitting from CAS to MBR increased energy consumption but not operating cost.• Retrofitting from CAS to MBR increased the net profit and cost efficiency.• The advantage of MBR is related to the adopted effluent standard.• The techno-economy of MBR improves with stricter effluent standards. While a growing number of wastewater treatment plants (WWTPs) are being retrofitted from the conventional activated sludge (CAS) process to the membrane bioreactor (MBR) process, the debate on the techno-economy of MBR vs. CAS has continued and calls for a thorough assessment based on techno-economic valuation. In this study, we analyzed the operating data of 20 large-scale WWTPs (capacity≥10000 m3/d) and compared their techno-economy before and after the retrofitting from CAS to MBR. Through cost-benefit analysis, we evaluated the net profit by subtracting the operating cost from the environmental benefit (estimated by the shadow price of pollutant removal and water reclamation). After the retrofitting, the removal rate of pollutants increased (e.g., from 89.0% to 93.3% on average for NH3-N), the average energy consumption increased from 0.40 to 0.57 kWh/m3, but the operating cost did not increase significantly. The average marginal environmental benefit increased remarkably (from 0.47 to 0.66 CNY/g for NH3-N removal), leading to an increase in the average net profit from 19.4 to 24.4 CNY/m3. We further scored the technical efficiencies via data envelopment analysis based on non-radial directional distance functions. After the retrofitting, the relative cost efficiency increased from 0.70 to 0.73 (the theoretical maximum is 1), while the relative energy efficiency did not change significantly. The techno-economy is closely related to the effluent standard adopted, particularly when truncating the extra benefit of pollutant removal beyond the standard in economic modeling. The modeling results suggested that MBR is more profitable than CAS given stricter effluent standards. 相似文献
• The synthesis and physicochemical properties of various CNMs are reviewed.• Sb removal using carbon-based nano-adsorbents and membranes are summarized.• Details on adsorption behavior and mechanisms of Sb uptake by CNMs are discussed.• Challenges and future prospects for rational design of advanced CNMs are provided. Recently, special attention has been deserved to environmental risks of antimony (Sb) element that is of highly physiologic toxicity to human. Conventional coagulation and ion exchange methods for Sb removal are faced with challenges of low efficiency, high cost and secondary pollution. Adsorption based on carbon nanomaterials (CNMs; e.g., carbon nanotubes, graphene, graphene oxide, reduced graphene oxide and their derivatives) may provide effective alternative because the CNMs have high surface area, rich surface chemistry and high stability. In particular, good conductivity makes it possible to create linkage between adsorption and electrochemistry, thereby the synergistic interaction will be expected for enhanced Sb removal. This review article summarizes the state of art on Sb removal using CNMs with the form of nano-adsorbents and/or filtration membranes. In details, procedures of synthesis and functionalization of different forms of CNMs were reviewed. Next, adsorption behavior and the underlying mechanisms toward Sb removal using various CNMs were presented as resulting from a retrospective analysis of literatures. Last, we prospect the needs for mass production and regeneration of CNMs adsorbents using more affordable precursors and objective assessment of environmental impacts in future studies. 相似文献