Search Results (11)

The reuse of Waste Foundry Sand (WFS) in construction remains constrained by fragmented research, unclear regulatory pathways, and inconsistent assessments of environmental safety and material performance. This study introduces a novel decision-making framework that systematically integrates mechanical performance metrics and leachate toxicity data to classify WFS into three categories: Approved, Reusable with Treatment, or Rejected. The framework is based on a bibliometric analysis of 822 publications and a meta-analysis of 45 experimental mix designs and 30 peer-reviewed leachate studies. Normalized compressive strength (NSR), water-to-cement (w/c) ratio, and heavy metal leachate concentrations are used as screening criteria. Thresholds are benchmarked against regulatory limits from the United States Environmental Protection Agency (EPA), the European Union Landfill Directive, and South Africa’s National Waste Standards. Validation using field data from a foundry in Gauteng Province, South Africa, confirms the framework’s practicality and adaptability. Results indicate that over 80 percent of WFS samples comply with environmental thresholds, and mixes with 10-to-30 percent WFS substitution often outperform control specimens in terms of compressive strength. However, leachate exceedances for cobalt and lead in certain chemically bonded sands highlight the need for batch-specific evaluation and potential treatment. The proposed framework supports data-driven, transparent reuse decisions that enhance environmental compliance and promote circular material flows in the built environment. Future work should focus on digital implementation, life-cycle monitoring, and expanding the framework to other industrial byproducts. Full article

Toxic cyanobacterial blooms are a growing environmental problem, persisting in freshwater bodies globally, and potentially hazardous to populations that rely on surface freshwater supplies. Nature-based solution units (NBSUs) are effective and sustainable approaches for water treatment, with sorption being an important process. The purpose of this study was to evaluate unmodified agro-based waste materials (rice husks, olive pulp pomace pellets (OP), cork granules) and the benchmark NBSU substrates (biochar, light expanded clay aggregate (LECA), and sand) for their microcystin-LR (MC-LR) and cylindrospermopsin (CYN) sorption potential. The kinetics and sorption mechanism of the two best sorbent materials were studied for future incorporation into NBSUs. Pre-screening of the sorbents showed highest sorption with biochar (>86% MC-LR and >98% CYN) and LECA (78% MC-LR and 80% CYN) and lower sorption with rice husk (<10%), cork (<10%), and sand (<26%). Leaching from OP made them unsuitable for further use. The sorption of both the cyanotoxins onto biochar was rapid (8 h), whereas onto LECA it was steadier (requiring 48 h for equilibrium). The pseudo-second-order kinetic model fit the sorption of both cyanotoxins onto biochar and LECA (R²: 0.94–0.99), suggesting that the sorption rate is limited by chemisorption. The sorption of MC-LR and CYN to biochar and LECA fit the Freundlich and D–R models better, suggesting multilayer sorption, high heterogeneity, and porosity in the sorbents (which was also confirmed by SEM/EDS). The sorption capacity was observed to be higher for biochar (K_f: MC-LR = 0.05, CYN = 0.16) than LECA (K_f: MC-LR = 0.02, CYN = 0.01). Full article

Pretreatment of reverse osmosis (RO) feed water of high mineral scaling propensity was evaluated with respect to downstream RO membrane scaling, for two different feed pretreatment configurations. The pretreatment schemes included (i) media sand filtration, followed by a hydrocyclone (HC) and (ii) a hydrocyclone, microfilter, and a UF module, where both configurations included mesh screens for added protection. The first pretreatment configuration reduced the source water turbidity to ~0.5 NTU, while treatment that included UF feed yielded turbidity of $\underset{˜}{<}0.1\mathrm{NTU}$; both pretreatment strategies provided feed water turbidity within the range recommended for RO desalination. Membrane scaling tests, with the pretreated water without antiscalant dosing, using a plate-and-frame RO unit and a membrane monitoring system, provided real-time membrane surface images that were quantified with respect to the progression of mineral scaling. RO desalting of source water pretreated with the first configuration revealed flux decline that was 75% greater and scale coverage (primarily gypsum) a factor of approximately eight higher relative to desalting of UF-treated source water. The results suggest that RO desalting of high mineral scaling propensity water can significantly benefit from added UF treatment to achieve feedwater turbidity to well below the typically recommended 0.5 NTU upper limit. Full article

Ecosystem services (ES) have been shrinking due to unreasonable development and utilization for a long time. There are many studies on ES, but the ecological information for policymakers is still complex and obscure. To address this critical omission, based on remote sensing data, combined with meteorological data, land use data, and administrative division data, using GIS spatial analysis technology and some ecological process models, we develop an ecosystem services radiation assessment framework (ESRAF) that can provide policymakers with concise and reliable ecological information. We illustrate the measurement of ESRAF through an application to specific regions of China’s national ecological sheltering zone (NESZ), showing that the approach can effectively identify the beneficiary areas (SBA) for sand-stabilization service, soil conservation service, and water conservation service, and the degree of sharing of ES of SBA. ES produced by ecosystems in a specific region not only generates huge benefits locally but also a large number of ES benefit surrounding regions through cross-regional transmission. Specifically, in 2015, the area benefiting from sand-stabilization service provided by the Ordos’s ecosystem is about $1.66\times {10}^6 \mathrm{k}{\mathrm{m}}^2$, the amount of dust reduction in SBA would reduce by $28,738.67\times {10}^4$ tons. The Loess Plateau Ecological Screen (LPES) provides critical soil conservation service, the SBA of LPES includes two parts: LPES and the Yellow River. The Northeast Forest Belt (NFB) provides vital water conservation services. The water conservation service beneficiary area is mainly located near the NFB, with 266 hydrological response units, covering an area of $8.982\times {10}^4 \mathrm{k}{\mathrm{m}}^2$. This study also showed that the transmission distance is inversely proportional to the radiation effect, that is, the benefit level decreases with the distance from SPA. According to the degree of sharing of ES of SBA, the proposed cross-regional differentiated ecological compensation scheme is helpful to promote regional sustainable development. At the same time, this study also shows that NESZ is of great significance for ensuring China’s ecological security. Full article

Chemical sand-fixing technology has shown good potential in preventing desertification, but the effect is determined by materials. In this paper, the adsorption behavior of quartz and six common polymer sand-fixing agents under dry conditions was studied by molecular dynamics method. The results show that all polymers could be adsorbed on the surface of quartz and their functional groups play an important role in the adsorption process. Compared with other materials, the binding energy and the number of hydrogen bonds of PAA-quartz composites were improved by 30.7–65.6% and 8.3–333.3%, respectively. It was found that the number of hydrogen bonds formed under the unit molecular was positively correlated with the mechanical properties of the improved sandy soil. This study provides an accurate, efficient and inexpensive qualitative evaluation method for the curing effect of sand fixers, which will assist in the screening and development of new high performance sand fixers. Full article

The large volume of industrial by-products and wastes from the construction, timber and paper industries has become a serious challenge worldwide. Recycling these industrial wastes as functional materials in the construction industry is an efficient approach for sustainable development. This study presents a pretreatment approach for recycling construction and demolition waste (CDW) and industrial side-streams (such as green liquor sludge, fiber waste, flotation sand and fly ash) in order to produce a geopolymer for the 3D printing of construction materials. A treatment approach was developed for screening the residues from CDW with a maximum size of 16 mm and for a combined line treatment for industrial side streams. The treatment processes utilized suitable and economical separation techniques for the recycling of waste materials. The crushing of the screened residues resulted in a homogeneous material size that facilitates the separation of mixed wastes and simplifies the classification of materials. The combined plant enabled the cost-effective treatment of various industrial wastes in a single process unit. The results show that the economic and environmental impact of the chosen techniques, in terms of their energy consumption, is highly dependent on the treatment line, separation technique and quantity of the individual waste that is processed. These recycled industrial wastes can be used as sustainable materials for the production of geopolymer concrete, contributing to the sustainability of the construction industry. Full article

Cemented sand and gravel (CSG) material is a new type of dam material developed on the basis of roller compacted concrete, hardfill, and ultra-poor cementing materials. Its main feature is a wide range of sources of aggregate (aggregate is not screened but by simply removing the large particles it can be fully graded on the dam filling) and low amounts of cementitious materials per unit volume. This dam construction material is not only economical and practical, but also green and environmentally friendly. There are many factors affecting the mechanical properties of CSG materials, such as aggregate gradation, sand ratio, water content, water–binder ratio, fly ash content, admixture content, etc. Based on the existing research results of the team, this paper focuses on the influence of fly ash content on the compressive strength of CSG materials. Through a large number of laboratory measured data, we found: (1) The compressive strength law of materials at different ages; the compressive strength of CSG material at age 90 d is generally 10%~30% higher than that at 28 d, and it is proposed that 90 d or 180 d strength should be used as the design strength in the design of CSG material dam; (2) There is an optimal value of fly ash content in CSG materials: when the fly ash content is 50% of the total amount of cementitious materials (cement + fly ash), the fly ash content is defined as the optimal content, and the test data are verified by regression analysis. The discovery of an ‘optimal dosage’ of fly ash provides an important reference for the design and construction of CSG dams. Full article

Effective multiphase flow and transport simulations are a critical tool for screening, selection, and operation of geological CO₂ storage sites. The relative permeability curve assumed for these simulations can introduce a large source of uncertainty. It significantly impacts forecasts of all aspects of the reservoir simulation, from CO₂ trapping efficiency and phase behavior to volumes of oil, water, and gas produced. Careful consideration must be given to this relationship, so a primary goal of this study is to evaluate the impacts on CO₂-EOR model forecasts of a wide range of relevant relative permeability curves, from near linear to highly curved. The Farnsworth Unit (FWU) is an active CO₂-EOR operation in the Texas Panhandle and the location of our study site. The Morrow ‘B’ Sandstone, a clastic formation composed of medium to coarse sands, is the target storage formation. Results indicate that uncertainty in the relative permeability curve can impart a significant impact on model predictions. Therefore, selecting an appropriate relative permeability curve for the reservoir of interest is critical for CO₂-EOR model design. If measured laboratory relative permeability data are not available, it must be considered as a significant source of uncertainty. Full article

Due to the shortage of natural sand from rivers and seas, artificial sand production from large stones or rocks is being increased. However, this sand manufacturing process is dangerous and causes several social problems such as a high level of unwanted vibrations or noises. This study investigates the vibration characteristics of sand and screen units in an artificial sand production plant whose operation is multiple with several actuators different exciting frequencies. As a first step, vibration levels are measured at the sand and screen unit positions using accelerometers in time and frequency domains. The measurement is carried out at two different conditions: activating only the sand unit and operating entire facilities such as a stone crusher. Vibration signals acquired from several locations of the sand and screen units of the plant are collected and analyzed from waveforms and spectrums of the signals. We identified that the vibration acceleration level of the screen unit is higher than that of the sand unit. In addition, it is found from the acceleration signals measured at the plant office and shipping control center (which are far away from the plant location) that the beating phenomenon arose due to close driving frequencies for several sand units. In this work, the vibration caused from the beating is significantly reduced by adjusting the driving frequencies for the sand units so that they are sufficiently scattered to avoid the beating. Full article

In the Midwestern United States, there is a strong management impetus toward reforestation to replace trees lost to due to tree mortality and to establish forests on previously cleared properties. Here, we describe a public outreach and volunteer effort that aimed to generate positive, community-engaged restoration outcomes and report on a practical experiment involving seed handling. We obtained tree seeds that were donated by members of the community to local land managers. We evaluated the size of the seeds collected and tested the influence of common stratification media (none, sand and vermiculite) and seed size on germination success of three tree genera involved in restoration efforts: Quercus, Carya and Juglans (oak, hickory and walnut). We found a species-specific effect of media on germination, such that Carya and Quercus showed little response to their stratification media, but Juglans had higher germination rates when stratified with vermiculite. Further, all genera of seeds germinated faster when stratified with either media than without. Thus, we suggest stratifying these seeds with media to promote germination success. We also tested for seed size as a predictor of mortality during stratification, following the logic that a size-based selection criterion might save time and space during stratification. We found species-specific impacts of seed size on germination, but relationships were highly variable, and we suggest avoiding screening seeds based on their size. In addition to these scientific results, we describe the broader forest restoration project, which may be a useful model for engaging the community in restoration efforts. Full article

Phlebotomus papatasi, an Old World sand fly species, is primarily responsible for the transmission of leishmaniasis, a highly infectious and potentially lethal disease. International travel, especially military rotations, between domestic locations and P. papatasi-prevalent regions in the Middle East poses an imminent threat to the public health of US citizens. Because of its small size and cryptic morphology, identification of P. papatasi is challenging and labor-intensive. Here, we developed a ribosomal DNA-polymerase chain reaction (PCR)-based diagnostic assay that is capable of detecting P. papatasi genomic DNA from mixed samples containing multiple sand flies native to the Americas. Serial dilution of P. papatasi samples demonstrated that this diagnostic assay could detect one P. papatasi from up to 255 non-target sand flies. Due to its simplicity, sensitivity and specificity, this rapid identification tool is suited for a long-term surveillance program to screen for the presence of P. papatasi in the continental United States and to reveal geographical regions potentially vulnerable to sand fly-borne diseases. Full article