Search Results (50)

Aerated accumulation bioreactors represent a promising alternative for the aerobic bioremediation of solid contaminated substrates. However, achieving homogeneous mixing and effective air distribution remains a key design challenge in solid-phase systems. This study presents the design and construction of a novel pilot-scale aerated bioreactor equipped with an angled-paddle agitation system, specifically developed to improve solid mixing and aeration. To evaluate the geometric configuration, a series of simulations were performed using the Discrete Element Method (DEM), with particle dynamics analyzed through the Lacey Mixing Index ($LMI$). Four paddle angles (0°, 15°, 45°, and 55°) were compared, with the 45° configuration achieving optimal performance, reaching $LMI$ values above 0.95 in less than 15 s and maintaining high homogeneity at a filling volume of 70%. These results confirm that the paddle angle significantly influences mixing efficiency in granular media. While this work focuses on engineering design and DEM-based validation, future studies will include experimental trials to evaluate biodegradation kinetics. The proposed design offers a scalable and adaptable solution for ex situ bioremediation applications. This work reinforces the value of integrating DEM simulations early in the bioreactor development process and opens pathways for further optimization and implementation in real-world environmental remediation scenarios. Full article

Modularised wall panels are increasingly used in building and construction. A new double-skin composite (DSC) wall system technology uses clinch seams to combine two roll-formed open section profiles into a hollow steel shell that is then filled with a light-weight concrete foam and can provide a fire-rated DSC solution for use in commercial and high-rise buildings. One important material parameter for the application is the panel performance in wind loading. This study presents a first fundamental analysis of the structural behaviour of the new DSC wall panel relevant to wind loading. For this, 3-point and 4-point bending tests combined with in situ camera analysis are performed and complimented with the analysis of seam strength and the concrete material parameters. The experimental results provide the first experimental evidence that the aerated concrete core material of the DSC panel only has a minor effect on the wall performance in bending. Most of the bending loads are absorbed by the tensile and compressive deformation of the steel outer shell and the shear deformation near the clinch seam. In this way, failure at maximum load is not initiated by concrete cracking but by steel sheet buckling or a mixed failure mode that combines steel buckling and seam opening. Full article

Spatio-temporal measurements of turbulent free surface flows remain challenging with in situ point methods. This study explores the application of an inexpensive depth-sensing RGB-D camera, the Intel^® RealSense™ D455, to capture detailed water surface measurements of a highly turbulent, self-aerated flow in the case of a stepped spillway. Ambient lighting conditions and various sensor settings, including configurations and parameters affecting data capture and quality, were assessed. A free surface profile was extracted from the 3D measurements and compared against phase detection conductivity probe (PDCP) and ultrasonic sensor (USS) measurements. Measurements in the non-aerated region were influenced by water transparency and a lack of detectable surface features, with flow depths consistently smaller than USS measurements (up to 32.5% less). Measurements in the clear water region also resulted in a “no data” region with holes in the depth map due to shiny reflections. In the aerated flow region, the camera effectively detected the dynamic water surface, with mean surface profiles close to characteristic depths measured with PDCP and within one standard deviation of the mean USS flow depths. The flow depths were within 10% of the USS depths and corresponded to depths with 80–90% air concentration levels obtained with the PDCP. Additionally, the depth camera successfully captured temporal fluctuations, allowing for the calculation of time-averaged entrapped air concentration profiles and dimensionless interface frequency distributions. This facilitated a direct comparison with PDCP and USS sensors, demonstrating that this camera sensor is a practical and cost-effective option for detecting free surfaces of high velocity, aerated, and dynamic flows in a stepped chute. Full article

With more than half of the world already living in urban spaces—a number set to increase in the coming decades—the need is clear to understand urban microclimates and extremes. This study placed twenty MX2302a HOBOmobile weather microsensors placed in aerated housings across the ~4 km² of the campus of the University of South Alabama from September to November 2022 and recorded temperature, relative humidity, and dewpoint every minute during the study period. These sensors were placed in situ, which allowed for the diversity in land cover, canopy cover, and aspect—large microclimatic drivers—to be captured. Sensors were compared to a campus mesonet station, part of the South Alabama Mesonet, a member of the National Mesonet Program. During the study period, temperatures were found to vary as much as 13 °C at the same minute across campus, with substantial changes in humidities and dewpoints also found. For example, the campus mesonet may have read 32 °C, yet the sensors could read as low as 29 °C and as high as 42 °C at the same moment. This study shows that the world is far more complex than what is seen at the mesoscale under idealized conditions, and the implications for society are considered. Full article

When exposed to different building environmental conditions, bio-composite materials, such as hemp mortars, represent a risk of mold proliferation. This later plays a critical role in the biodeterioration of the materials when their physical properties are locally modified by the natural aging process. The primary objectives of the present work are first to assess the evolution of the surface of contaminated mortar; second, to investigate an accurate DNA extraction method that could be used for both bio-composite mortars and their fiber sources collected in situ; then, to understand the process of the proliferation of mold strains on both hemp shives and hemp mortar; and finally, to compare mold strains present in these phases to show their relationship to mold contamination and their impact on human health. In situ hemp mortar contamination behavior was investigated in the region of Pau (France) two months after hemp mortar application in extreme conditions (high humidity, low temperature, no aeration), which did not match the standard conditions under which hemp mortar must be used. The SEM observations and FTIR and pH analyses highlighted the decrease in pH level and the presence of organic matter on the mortar surface. DNA sequencing results showed that hemp shives were the main source of fungal contamination of hemp mortar. A mold population analysis showed that the most dominant phylum was Ophistokonta, which represented 83.6% in hemp shives and 99.97% in hemp mortar. The Acrostalagmus genus representatives were the most abundant, with 42% in hemp shives and 96% in hemp mortar. The interconnection between the mold strain characteristics (particularly the ability to grow in extreme environments) and the presence of hemp mortar was emphasized. Full article

To achieve the in situ capacity expansion of the post-denitrification biological aerated filter (BAF-DN), the integration of BAF with the anammox process (BAF/AX) was proposed. With the objective of maximizing retaining ammonia nitrogen, the operational optimization of BAF was achieved by two distinct strategies. The treatment performance of BAF demonstrated that the removal efficiencies of chemical oxygen demand (COD) and ammonia nitrogen (${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$) was 66.3~67.3% and 4~12%, respectively, under conditions of low aeration intensity (0.4 m³·m⁻²·h⁻¹) or a shortened empty bed residence time (EBRT) of 30 min. Residual ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ in the BAF effluent served as the ammonia substrate for the subsequent anammox process, which was successfully launched by using ceramic particles and sponges as carriers. Notably, the sponge carrier facilitated a shorter start-up period of 41 to 44 days. Furthermore, the sponge-based anammox reactor exhibited a superior ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ removal capacity (≥85.7%), under operations of a shorter EBRT of 40 min, low influent ${\mathrm{NH}}_4^{+}\text{-}\mathrm{N}$ concentrations (≤30 mg/L), and COD levels of ≤67 mg/L. In addition, a comprehensive evaluation of the BAF/AX process was conducted, which considered performance, cost-effectiveness, and engineering feasibility. The performance results illustrated that the effluent quality met the standard well (with a COD level of ≤ 50 mg/L, and a TN of ≤3.1~10.5 mg/L). Following a comparison against the low aeration intensity operation, it was recommended to operate BAF at a low EBRT within the BAF/AX process. Consequently, the treated volume was double the volume of the standalone BAF-DN, synchronously achieving low costs (0.413 yuan/m³). Full article

Marine eutrophication, primarily driven by nutrient over input from agricultural runoff, wastewater discharge, and atmospheric deposition, leads to harmful algal blooms (HABs) that pose a severe threat to marine ecosystems. This review explores the causes, monitoring methods, and control strategies for eutrophication in marine environments. Monitoring techniques include remote sensing, automated in situ sensors, modeling, forecasting, and metagenomics. Remote sensing provides large-scale temporal and spatial data, while automated sensors offer real-time, high-resolution monitoring. Modeling and forecasting use historical data and environmental variables to predict blooms, and metagenomics provides insights into microbial community dynamics. Control treatments encompass physical, chemical, and biological treatments, as well as advanced technologies like nanotechnology, electrocoagulation, and ultrasonic treatment. Physical treatments, such as aeration and mixing, are effective but costly and energy-intensive. Chemical treatments, including phosphorus precipitation, quickly reduce nutrient levels but may have ecological side effects. Biological treatments, like biomanipulation and bioaugmentation, are sustainable but require careful management of ecological interactions. Advanced technologies offer innovative solutions with varying costs and sustainability profiles. Comparing these methods highlights the trade-offs between efficacy, cost, and environmental impact, emphasizing the need for integrated approaches tailored to specific conditions. This review underscores the importance of combining monitoring and control strategies to mitigate the adverse effects of eutrophication on marine ecosystems. Full article

Direct ultrafiltration (UF) is anticipated to be a promising technology for rural water supply due to its stable permeate quality and ease of automatic operation & maintenance. However, seasonal high turbidity in the surface water resources caused severe membrane fouling, resulting in the requirement of frequent cleaning of the UF process, and limiting the broad application of the direct UF in treating rural surface water. To address this issue, this study investigated the feasibility and mechanism of in situ aeration in alleviating the UF membrane fouling in treating surface water with high turbidity (200, 500, and 800 NTU). The results indicated that with the weak aeration (0.4 m³/(m²·min)), the concentration of polysaccharides accumulated on the membrane surface was high, and serious membrane fouling was observed. With medium aeration (0.8 and 1.2 m³/(m²·min)), bubble shear force could effectively reduce the foulants accumulated on the membrane surface to alleviate the membrane fouling. During the whole experiment, the optimal group (1.2 m³/(m²·min)) showed a 45% lower TMP compared to the control. However, strong aeration (1.6 m³/(m²·min)) caused floc breakage and was less conducive to the membrane fouling control compared to the medium aeration. Furthermore, under in situ aeration, the contents of polysaccharide accumulated on the membrane surface and deposited in the membrane pores were reduced by 8.85%~49.29%, and the structures of the cake layer turned out to be porous and permeable, implying that in situ aeration could significantly modify the structure and composition of the cake layer, contributing to the UF membrane fouling control in treating the seasonal high-turbidity surface water. These findings will provide novel approaches for the application of UF technology in rural water supply. Full article

Methane (CH₄) is one of the potent greenhouse gases emitted from municipal wastewater treatment plants. The characteristics of methane emission from municipal wastewater treatment plants (WWTPs) have attracted lots of concern from related researchers. The present work investigated the source of methanogens and methane emission properties from two WWTPs in Xi’an, and one is employed in an Orbal oxidation ditch, and the other is anaerobic/anoxic/oxic (A/A/O). The measurement of specific methanogenic activity (SMA) and coenzyme F₄₂₀ concentration, together with Fluorescence in situ hybridization (FISH), was used to determine the amount and activity of methanogens in two WWTPs. Additionally, a combined activated sludge model was built and predicted the growth of methanogens and other key microorganisms in the sludge. The results showed that the average CH₄ emission flux from the Orbal oxidation ditch (22.74 g CH₄ /(m²·d)) was much higher than that from A/A/O (9.57 g CH₄/(m²·d)). The methane emission factors in the Orbal oxidation ditch and A/A/O processes were 1.18 and 0.21 g CH₄ /(m³ INF), respectively. These distinct methane emission characteristics between two WWTPs are mainly attributed to the higher activity and content of methanogens, as well as the discontinuous aeration in the Orbal oxidation ditch. Additionally, dissolved oxygen concentration, water temperature, and the presence of nitrate/nitrite were also important factors that influenced methane emission. The FISH analysis showed that Methanococcus was the dominant methanogen in both WWTPs. In addition, the combined model successfully simulated the growth of methanogens in WWTPs. Methanogens in WWTPs were mainly derived from the sewer system, and the cumulative effect led to an increase in the abundance of methanogens in activated sludge. The outcomes of this study provide new insights in the prediction and management of GHG emission from WWTPs. Full article

Harmful cyanobacterial blooms pose a serious environmental threat to global water ecology and drinking water safety. Microcystis aeruginosa, a dominant cyanobacterial species in cyanobacterial blooms, was removed using the electro-flocculation–electro-Fenton (EC-EF) technology. In the EC-EF system, the iron anode was used as a sacrificial anode to produce iron ions in situ. Combining the aeration device with the graphite felt cathode as one unit realizes a direct and effective air supply to the cathode, and improves the electrical Fenton efficiency for generating oxidizing groups such as hydroxyl radicals. The cyanobacteria removal efficiency was up to 94.6% under optimal process conditions with a current density of 1.08 mA/cm², an electrolysis time of 5 min, and an aeration flow rate of 0.06 L·min⁻¹. At the same time, the microcystins (MCs) and total organic carbon (TOC) content in the water were controlled. The mechanism of cyanobacterial cell removal using this EC-EF system was investigated via characterization of cyanobacterial cells and flocs and cell membrane permeability analysis. The moderate oxidation and iron hydroxide encapsulation of this system are both beneficial to maintaining the integrity of cyanobacterial cells. The results demonstrated that EC-EF is a chemical-free and eco-friendly cyanobacteria removal technology. Full article

Landfills have long been widely used to dispose of Municipal Solid Waste (MSW). However, many landfills have faced early closure issues in recent years due to overload operations. Although in-situ aeration technology can quickly stabilize MSW, low oxygen utilization rates present a general problem that results in high energy-consuming and operating costs. This research aims to improve oxygen utilization efficiency by observing the dynamic respiratory index and the removal of contaminants. Three continuous reactors were constructed and designed with targeted aeration and re-circulation schemes for different landfill ages. The results show that a well-designed aerobic, semi-aerobic, and anaerobic reactor can fully degrade the organic components of MSW with different landfill ages, and the quantity of waste has been reduced by more than 60%. Additionally, it was disclosed that gas-water joint technology has a promotional effect on activating microorganisms. Full article

In this work, we report the restoration of a polluted urban stream by employing the multistage vortex aerator (MVA), an in-line mixer device that improves the dissolved oxygen concentration of polluted streams and accelerates the water purification rate. It was observed during the field experiment that the dissolved oxygen was enhanced up to 7.05 mg/L and the water quality was improved to a good grade. As a result, the complex odor was successfully eliminated and reduced by up to 71.9%, while the water quality grade was also improved by more than two grades on average. Stream water quality indicators monitored for twelve months revealed high removal rates of total phosphorous (56.4%) and suspended solids (61%). The study demonstrated MVA as a promising eco-friendly technology for significant improvement in urban stream water quality. Moreover, the MVA process creates no secondary pollution and is believed to be a sustainable treatment option for odorous water bodies. Overall, the MVA process is technically feasible for implementation, and this study provides a specific reference as a basis for the treatment of polluted water bodies in urban settings. Full article

Identifying and ensuring the inactivation of the African Swine Fever virus in deadstock is a gap in the swine industry’s knowledge and response capabilities. The results of our study demonstrate that ASFv in deadstock was inactivated using static aerated composting as the carcass disposal method. Replicated compost piles with whole market hogs and two different carbon sources were constructed. In-situ bags containing ASFv-infected spleen tissue were placed alongside each of the carcasses and throughout the pile. The bags were extracted at days 0, 1, 3, 7, 14, 28, 56, and 144 for ASFv detection and isolation. Real-time PCR results showed that DNA of ASFv was detected in all samples tested on day 28. The virus concentration identified through virus isolation was found to be below the detection limit by day 3 in rice hulls and by day 7 in sawdust. Given the slope of the decay, near-zero concentration with 99.9% confidence occurred at 5.0 days in rice hulls and at 6.4 days in sawdust. Additionally, the result of virus isolation also showed that the virus in bone marrow samples collected at 28 days was inactivated. Full article

In order to improve the removal efficiency of refractory organic matters in micro-polluted source water, biological manganese oxides (BMOs) were generated in situ in the biological aerated filter (BAF) (BAF 2^#), which could oxidize the refractory organic matters into biodegradable organic matters. COD_Mn and NH₄⁺-N in the effluent of BAF 2^# both stabilized on the 39th day, while COD_Mn and NH₄⁺-N in the effluent of the control BAF (BAF 1^#) stabilized on the 38th and 42nd days, respectively. In the steady phase, the removal rates of COD_Mn and NH₄⁺-N in BAF 1^# were 41.51% and 94.79%, respectively, while in BAF 2^#, they were 54.52% and 95.55%, respectively. BMOs generated in BAF 2^# evidently improved the efficiency of COD_Mn removal. With the increase in the influent Mn²⁺ in BAF 2^#, the rate of COD_Mn removal was gradually improved to 63.60%, while the efficiency of NH₄⁺-N removal was slightly improved, COD_Mn was evidently removed in each section of the filter layer, and ammonia was mainly removed in the 0~0.8 m layer of the filter. COD_Mn was evidently removed in each section of the filter layer, and NH₄⁺-N was mainly removed in the 0~0.8 m layers of the filter. Biological COD_Mn, Mn²⁺, and NH₄⁺-N removal all followed the first-order kinetic reaction. As the influent Mn²⁺ gradually increased from 0 to about 0.5, 1, and 2 mg/L, the efficiency of COD_Mn removal along the filter layer was significantly improved, but the efficiency of NH₄⁺-N removal was slightly improved. The kinetic constant k of biological COD_Mn removal significantly increased, while the kinetic constant k of biological Mn²⁺ and NH₄⁺-N removal gradually increased. Full article

Water quality deterioration is a major problem faced by reservoirs globally, owing to the inflow of pollution from industrial and municipal activities. Water-lifting aeration is an in situ water quality improvement technology that mixes and oxygenates deep water bodies in reservoirs to improve pollution control efficiency and water quality. While previous studies have mainly focused on the mixing process in the reservoir outside the water-lifting aerator (WLA), knowledge of the internal flow remains limited. In this study, a two-phase flow within a WLA system was numerically studied using the volume of fluid (VOF) method to comprehensively analyze the internal two-phase flow characteristics and the influence on the water-lifting and oxygenation performance of the system. The statistical analysis results showed that increasing the aeration chamber volume enhanced the bottom oxygenation performance by 27% because of the prolonged time of the deflector plate outlet outflow. Additionally, increasing the air release rate enhanced the water-lifting performance by 47%, which was induced by the shortened air piston release period. This study demonstrates the internal flow mechanism of the WLA and provides technical support for parameter optimization design, which has significant scientific research and engineering application value. Full article