Fast flow simulation study of pulsating ventilation performance on air contaminant removal

Fast flow simulation is imperative in the design of pulsating ventilation,which is potentially efficient in indoor air contaminant removal.The execution of the conventional CFD method requires considerable amount of computational resources.In this study,five different numerical schemes were proposed based on fast fluid dynamics(FFD)and fractional step(FS)methods,and were evaluated to achieve quick simulation of airflow/contaminant dispersion.One of these numerical schemes was identified with the best overall computing efficiency for investigating the performance of pulsating ventilation.With this numerical scheme at hand,the air contaminant removal effectiveness of different ventilation types was evaluated.Two kinds of pulsating ventilation and one kind of steady ventilation were tested upon a benchmark isothermal mixing chamber.The effect of adjusting supply velocity parameters on the ventilation performance was also investigated.CO_(2)concentration,airflow pattern,and vortex structure of different ventilation types were illustrated and analyzed.The results reveal that the FS method is more suitable for transient simulation of wall-bounded indoor airflow than the FFD method,and 34%–51%of computing time could be saved compared to the conventional CFD method.Regarding the choice of ventilation type,steady ventilation might result in short-circuit airflow and stagnant zones;alternatively,pulsating ventilation has greater potential in air contaminant removal due to its ever-changing vortex structure.

Growth and Contaminant Removal Effect of Several Plants in Constructed Wetlands

The aim of the present study is to probe the relation between plant growth and its decontamination effect in constructed wetlands. Four species were studied in the small-scale mono-cultured constructed wetlands, which were fed with domestic wastewater. Plant growth indexes were correlated with contaminant removal performance of the constructed wetlands. Wetlands planted with Cyperus flabelliformis Rottb. showed the highest growth indexes such as shoot growth, biomass, root activity, root biomass increment, and the highest contaminant removal rates, whereas wetlands planted with Vetiveria zizanioides L. Nash had the lowest growth indexes and the lowest removal rates. Above-ground biomass and total biomass were significantly correlated with ammonia nitrogen removal, and below-ground biomass with soluble reactive phosphorus removal. Photosynthetic rate had higher correlation with nitrogen removal in these species. Root activity and root biomass increment was more correlated with 5 d biochemical oxygen demand removal. Chemical oxygen demand removal had lower correlations with plant growth indexes. All four species had higher removal rates in summer and autumn. The results suggest that the effect of plant growth on contaminant removal in constructed wetlands were different specifically in plants and contaminants.

Water self-purification via electron donation effect of emerging contaminants arousing oxygen activation over ordered carbonenhanced CoFe quantum dots

The release of emerging contaminants(ECs)into aquatic environments poses a significant risk to global water security.Advanced oxidation processes(AOPs),while effective in removing ECs,are often resource and energy-intensive.Here,we introduce a novel catalyst,CoFe quantum dots embedded in graphene nanowires(CoFeQds@GN-Nws),synthesized through anaerobic polymerization.It uniquely features electron-rich and electron-poor micro-regions on its surface,enabling a self-purification mechanism in wastewater.This is achieved by harnessing the internal energy of wastewater,particularly the bonding energy of pollutants and dissolved oxygen(DO).It demonstrates exceptional efficiency in removing ECs at ambient temperature and pressure without the need for external oxidants,achieving a removal rate of nearly 100.0%.The catalyst's structure-activity relationship reveals that CoFe quantum dots facilitate an unbalanced electron distribution,forming these micro-regions.This leads to a continuous electrondonation effect,where pollutants are effectively cleaved or oxidized.Concurrently,DO is activated into superoxide anions(O_(2)^(·-)),synergistically aiding in pollutant removal.This approach reduces resource and energy demands typically associated with AOPs,marking a sustainable advancement in wastewater treatment technologies.

Recent studies of Pickering emulsion system in petroleum treatment:The role of particles

Pickering emulsions stabilized by solid particles have gained much attention,which afford high stability,low toxicity,controllable rheological properties and stimuli-responsive behavior compared to the traditional emulsions emulsified by surfactants.Those particles,as the core parts of the emulsion systems,play an important role in the fabrication and application of Pickering emulsion systems,making them attractive in petroleum fields.In this review,the influence of various particles on the stability and properties of Pickering emulsion systems as well as recent researches associated with the stimuliresponsibility of Pickering emulsion systems are introduced.Specifically,the design of functional particles and Pickering emulsion systems with super stabilities and controllable rheological properties are listed.Furthermore,some petroleum application of Pickering emulsion systems for enhanced oil recovery and spilled oil collection as well as the application as soft templates to fabricate oil-absorbing material and as three-phase microreactors that most likely for petroleum application are discussed,and the issues hindering the actual application of Pickering emulsion systems are also evaluated.This review charts a way for Pickering emulsion studies that could lead to a valid petroleum application through design of the particles served as the enhancers of Pickering emulsion stability for purpose of tailoring chemical flooding.

Wastewater degradation by iron/copper nanoparticles and the microorganism growth rate

Nowadays, trends in wastewater treatment by zero-valent iron（ZVI） were turned to use bimetallic NZVI particles by planting another metal onto the ZVI surface to increase its reactivity. Nano size zero-valent iron/copper（NZVI/Cu0） bimetallic particles were synthesized in order to examine its toxicity effects on the wastewater microbial life, kinetics of phosphorus, ammonia stripping and the reduction of chemical oxygen demand（COD）.Various concentrations of NZVI/Cu0 and operation conditions both aerobic and anaerobic were investigated and compared with pure NZVI experiment. The results showed that addition10 mg/L of NZVI/Cu0 significantly increased the numbers of bacteria colonies under anaerobic condition, conversely it inhibited bacteria activity with the presence of oxygen. Furthermore,the impact of nanoparticles on ammonia stripping and phosphorus removal was also linked to the emitted iron ions electrons. It was found that dosing high concentration of bimetallic NZVI/Cu0 has a negative effect on ammonia stripping regardless of the aeration condition. In comparison to control, dosing only 10 mg/L NZVI/Cu0, the phosphorus removal increased sharply both under aerobic and anaerobic conditions, these outcomes were obtained as a result of complete dissolution of bimetallic nanoparticles which formed copper-iron oxides components that are attributed to increasing the phosphorus adsorption rate.

A critical review of biochar-based nitrogen fertilizers and their effects on crop production and the environment

Globally,nitrogen(N)fertilizer demand is expected to reach 112 million tonnes to support food production for about 8 billion people.However,more than half of the N fertilizer is lost to the environment with impacts on air,water and soil quality,and biodiversity.Importantly,N loss to the environment contributes to greenhouse gas emissions and climate change.Nevertheless,where N fertilizer application is limited,severe depletion of soil fertility has become a major constraint to sustainable agriculture.To address the issues of low fertilizer N use efficiency(NUE),biochar-based N fertilizers(BBNFs)have been developed to reduce off-site loss and maximize crop N uptake.These products are generally made through physical mixing of biochar and N fertilizer or via coating chemical N fertilizers such as prilled urea with biochar.This review aims to describe the manufacturing processes of BBNFs,and to critically assess the effects of the products on soil properties,crop yield and N loss pathways.