Effectiveness of Design and Implementation Alternatives for Stormwater Control Measures Modeled at the Watershed Scale.

To evaluate the effectiveness of dispersed stormwater control measures (SCMs), it is important to consider groundwater-surface water interactions and their consequences for stream hydrologic responses relevant to channel geomorphic stability and ecology. This study aimed to evaluate the effectiveness of different SCM design scenarios and implementation alternatives on exceedance levels and volumes of streamflow at the watershed scale. For this purpose, a process-based block-connector model of Sligo Creek, an urban watershed (29 km2) in the suburbs of Washington, DC, was used to study the effects of SCM system design on the stream hydrograph. The watershed has 34% impervious area (IA), which was discretized into 14 similar-sized subwatersheds, each consisting of pervious and impervious surface areas. Each subwatershed was compartmentalized with the representative overland flow, unsaturated flow, groundwater blocks, and links to main channel segments. The model was calibrated and validated to existing conditions using a 3-year time series of observed flow data. Afterward, a predevelopment simulation was configured. Three SCM unit designs and IA diversions through the SCM retrofit system were simulated. The three unit design scenarios represented a simple pond with surface storage and overflow or SCMs that infiltrate with an engineered soil layer and with or without an underdrain pipe. Differences among the model simulations were evaluated using flow exceedance probability curves. The area of the SCM system was modeled as 5% of the IA retrofit. Three implementation levels, including 10%, 50%, and 90% of the IA diverted through SCMs, were considered for each SCM unit design. The results showed that at least a 50% retrofit of runoff from IA watershedwide would be needed to achieve similar predevelopment base flows and peak flows. Intermediate flows could not be matched but were closest for the infiltration with the underdrain pipe design scenario. It was also found that concentrating the SCMs in the lower portion of the watershed resulted in more effectively achieving the predeveloped exceedance curves than uniform SCM implementation. The results are relevant to planning-level decisions that depend on effectiveness predictions of different SCM unit designs and implementation alternatives in developed watersheds.

Adsorption process modeling to reduce COD by activated carbon for wastewater treatment.

Investigations have been carried out on the utilization of Activated Carbon (AC) in adsorption processes for the wastewater treatment of industry and municipal. Sulfides materials, phenols and furfural is a toxic compounds in wastewater from refineries can adversely affect the performance of biological aeration basins in reducing COD levels. This work aims to provide the effectiveness of AC in reducing the COD level of the effluent from the Dissolved Air Flotation (DAF) unit to meet standards of environments protecting and pass the design of wastewater treatment plants. A dynamic adsorption model was developed based on the dispersion of axial in the AC packed bed, assuming that the LDF (linear driving force) model in to the adsorbents is agreed to mass transfer. The model's predictions of chemical oxygen demand breakthrough curve concentrations showed excellent agreement with experimental data. The sensitivity analysis of operational conditions such as flow rate, inlet concentration of COD and bed length was used to gain a better understanding of the optimal design of an AC fixed bed. The results suggest that an AC fixed bed can complement biological treatment of wastewater and address the challenges faced by biological basins in oil refineries.

Techno-economic and environmental optimization of a combined regenerated gas turbine and supercritical CO2 cycle based on methane and hydrogen mixture as fuel for environmental remediation.

Achieving power generation systems with high efficiency and low emission of environmental pollutants is one of the requirements of a sustainable environment. In this study, a hybrid power generation system based on gas turbine (GT) with regenerator configuration is introduced. A supercritical carbon dioxide (sCO2) cycle is used to recover the waste heat from GT exhaust gases. In order to reduce the emission of environmental pollutants, the combination of hydrogen and methane is used as GT fuel. In order to investigate the effect of using hydrogen in the fuel composition, the fraction of hydrogen is changed between 0 and 50% and its effect on performance, environmental, and economic factors is investigated. Also, the effect of design parameters such as compressor pressure ratio (CPR) and turbine inlet temperature (TIT) of GT and sCO2 cycles on exergy efficiency, total cost rate (TCR), and normalized pollutants emission index are investigated. Then, by performing a bi-objective optimization process with the aim of achieving maximum exergy efficiency and minimum TCR, the optimal operating point is extracted. At the optimal operating point, exergy efficiency is 44% and TCR is 6 dollars/second.

Mechanical Performance of Fly Ash Based Geopolymer (FAG) as Road Base Stabilizer.

This study examines the strength development of fly ash-based geopolymer (FAG) as a stabilizer for road base material for pavement construction. In the last decade, there has been a rapid development of conventionally treated bases, such as cement-treated bases. However, a major problem with this kind of application is the shrinkage cracking in cement-treated bases that may result in the reflection cracks on the asphalt pavement surface. This study explores the effects of FAG on base layer properties using mechanistic laboratory evaluation and its practicability in pavement base layers. The investigated properties are flexural strength (FS), unconfined compressive strength (UCS), shrinkage, and resilient modulus (RM), as well as indirect tensile strength (ITS). The findings showed that the mechanical properties of the mixture enhanced when FAG was added to 80-85% of crushed aggregate, with the UCS being shown to be a crucial quality parameter. The effectiveness of FAG base material can have an impact on the flexible pavements' overall performance since the base course stiffness directly depends on the base material properties. As a stabilizing agent for flexible pavement applications, the FAG-stabilized base appeared promising, predicated on test outcomes.

Geopolymer-Based Artificial Aggregates: A Review on Methods of Producing, Properties, and Improving Techniques.

The depletion of aggregate-related natural resources is the primary concern of all researchers globally. Recent studies emphasize the significance of recycling and reusing various types of natural or by-product material waste from industry as a result of the building industry's rising demand for aggregate as the primary component in concrete production. It has been demonstrated that the geopolymer system has exceptional features, such as high strength, superior durability, and greater resistance to fire exposure, making it a viable alternative to ordinary Portland Cement (OPC) concrete. This study will examine the present method utilized to generate artificial aggregate-based geopolymers, including their physical and mechanical properties, as well as their characterization. The production process of geopolymer derived from synthetic aggregates will be highlighted. In conjunction with the bonding of aggregates and the cement matrix, the interfacial transition zone (ITZ) is highlighted in this work as an additional important property to be researched in the future. It will be discussed how to improve the properties of geopolymers based on artificial aggregates. It has been demonstrated that cold bonding provides superior qualities for artificial aggregate while conserving energy during production. The creation of ITZ has a significant impact on the bonding strength between artificial aggregates and the cement matrix. Additionally, improvement strategies demonstrate viable methods for enhancing the quality of manufactured aggregates. In addition, other recommendations are discussed in this study for future work.

Waste Material via Geopolymerization for Heavy-Duty Application: A Review.

Due to the extraordinary properties for heavy-duty applications, there has been a great deal of interest in the utilization of waste material via geopolymerization technology. There are various advantages offered by this geopolymer-based material, such as excellent stability, exceptional impermeability, self-refluxing ability, resistant thermal energy from explosive detonation, and excellent mechanical performance. An overview of the work with the details of key factors affecting the heavy-duty performance of geopolymer-based material such as type of binder, alkali agent dosage, mixing design, and curing condition are reviewed in this paper. Interestingly, the review exhibited that different types of waste material containing a large number of chemical elements had an impact on mechanical performance in military, civil engineering, and road application. Finally, this work suggests some future research directions for the the remarkable of waste material through geopolymerization to be employed in heavy-duty application.

Epidemiology of depression and anxiety among undergraduate students.

AIMS: Depression and anxiety are the most common and prevalent mental health issues among undergraduate students. This study aimed to investigate the prevalence of anxiety and depression, their associated predictors, and to assess knowledge and use of antidepressant medications among university students in Jordan. METHODS: A cross-sectional survey-based study was conducted in Jordan among undergraduate students from all levels of study. Istilli et al's questionnaire, the PHQ-9 and generalised anxiety disorder (GAD) scales were used in this study to explore the study objectives. Logistic regression analysis was used to identify predictors of anxiety and depression. RESULTS: A total of 1582 undergraduate students participated in the study. Prevalence of depression was 22.3% (n = 330), with proportions of minimal, mild, moderate, moderately severe and severe depression to be 15.9%, 32.4%, 29.5%, 14.7% and 7.6%, respectively. Prevalence of anxiety was 15.8% (n = 173), with proportions of mild, moderate and severe anxiety to be 46.4%, 37.8% and 15.8%, respectively. Female students and those with low income (<500 JD) had higher depression mean scores compared with others. Females, arts and engineering students, divorced and those who have four or more children had higher anxiety mean scores compared with others. CONCLUSION: Findings of this study addressed the importance of taking serious measures and interventions to prevent the development of severe mental illness among university students.