Configuration influence in relation to fluid flow of venturi system

Due to its simplicity and accurately measuring the flow rate, the venturi system is a special kind of pipe that is widely used in various applied fluid mixtures. One of the venturi system's important applications is ejectors devices that accurately facilitate adding air to water to sustain oxygen demand target levels in many waterworks engineering systems. This study aims to improve venturi system measurement accuracy through experimental investigation and analytical analysis for the venturi system conditional configuration parameters effect on target aeration operational efficiency. In the experiment work, different runs are implemented to characterize the performance of such aerators by describing the impact of venturi characteristics and configurations, including water flow rate, air inlets orifices diameters, inlet velocities, throat lengths, inlet angles, outlets angles, and outlet diameters on aeration efficiency. Results show that the venturi air vent diameter is an important governing parameter for determining aeration performance value. Additionally, an indicated increase in aeration performance with an increasing throat length to its diameter ratio. Meanwhile, the results revealed a varying noted effect of the venturi system characteristics and configurations on aeration performance. Moreover, the equations that relate venturi system configuration and Reynolds numbers with the aeration operational performance are developed to facilitate the target accurate aeration efficiency estimation.     

Screening level modeling of long-term impact of petroleum hydrocarbon contamination on fresh groundwater lenses in the Arabian Gulf region

The Gulf War in 1991 created an environmental catastrophe, one of the major consequences of which was setting several oil wells on fire in the Arabian Gulf area. The total oil spilled as a result of the damaged wells was about 3.5 × 10⁶ m³. Out of these, 3.3 × 10⁶ m³ of oil was recovered and exported. The rest was left behind as it was not economical to collect. The oil left behind was subject to severe weathering over the past ten years. Soil and subsurface contamination pose a serious risk to the quality of the already scarce fresh groundwater resources in the area which was subject to oil spill in the study region. This paper presents the computer modeling activities carried out towards simulating the transport of the hydrocarbon contamination of the fresh groundwater resources at a study area in the Arabian Gulf region, and predicting the contamination levels at the fresh groundwater lenses in the area in the future, should current contamination levels persist in the soil and groundwater. The modeling activities relied on both semi-analytical and numerical flow and transport models.     

Assessment of human health risks and pollution index for heavy metals in farmlands irrigated by effluents of stabilization ponds

Areas contaminated with heavy metals can pose major risks to human health and ecological environments. The aims of this study are to assess human health risk and pollution index for heavy metals in agricultural soils irrigated by effluents of stabilization ponds in Birjand, Iran. The results revealed that the levels of Cr, Mn, Zn, Fe, Cu, Cd, and Pb were in range of 70.3–149.65, 355–570, 31.15–98.45, 23,925–29,140, 22.75–25.95, 0.17–6.51, and 8.5–23.5 mg/kg in topsoils, respectively. Total hazard index values from heavy metals through three exposure routes for adults and children were 9.13E−01 and 1.10, respectively, indicating that there was non-carcinogenic risk for children. The total risk of carcinogenic metals (Cr, Cd, and Pb) through the three exposure routes for adults and children was 1.06E−04 and 9.76E−04, respectively, which indicates that the metals in the soil will not induce carcinogenic risks to these age groups. Pollution levels of heavy metals in soil samples including enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geo-accumulation index (Igeo) showed heavy metal contamination of agricultural soils. The results of the present study provide basic information about heavy metal contamination control and human health risk assessment management in the study area.     

Biodegradation of low-density polyethylene (LDPE) using the mixed culture of Aspergillus carbonarius and A. fumigates

Low-density polyethylene (LDPE) possesses various applications in several industries owing to its durability, low-cost, and many mechano-thermal properties. Unfortunately, LDPE waste creates an environmental threat. The level of biodegradation of black LDPE sheets with fungi isolated from different landfills sites in Sharqiyah Governorate, Egypt, was evaluated. LDPE sheets, the only source of carbon, along with minimal salt medium were incubated on a rotary shaker at 30 °C and 120 rpm for 16 weeks. Aspergillus carbonarius MH 856457.1 and A. fumigatus MF 276893 confirmed to be good candidates for LDPE biodegradation. A mixed culture of two strains showed the excellent weight loss% of sheets as compared to single isolate. Further efforts to improve the degrading capacity through physical and chemical treatments were performed. The biodegradation was significantly stimulated by 39.1% (thermal treatment), 17.76% (HNO₃ treatment), and 5.79% (Gamma-irradiation treatment). Laccases and manganese peroxidases activities were assayed. LDPE biodegradation was analyzed by scanning electronic microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and gas chromatography–mass spectrometry (GC–MS). FTIR spectra showed the appearance of new functional groups assigned to hydrocarbon biodegradation and confirmed the role of manganese peroxidase in process. The changes in the FTIR spectra of the mixed culture biomass before and after the biodegradation (Δ73 cm^?1) and the surface changes in the biodegraded LDPE (as indicated from SEM) confirmed the depolymerization of LDPE. From GC–MS analysis, the plasticizers bis(2-ethylhexyl) phthalate, Diisssctyl phthalate, 1,2-benzenedicarboxylic acid diisooctyl ester, and tributyl acetylcitrate completely biodegraded. Moreover, several antioxidants, antimicrobial, and anticancer compounds, and methyl esters of fatty acids were produced.

     

Flooding and the interannual variability of hydrologic quantities in the Missouri River basin

The six mainstem reservoirs in the Missouri River basin (MRB) are managed mainly to prevent flooding from snowmelt and heavy rainfall, a goal for which the interannual variabilities of precipitation ($P$), evapotranspiration ($\mathit{ET}$), and surface air temperature ($T_{\mathrm{air}}$) are vitally important. We tested the hypothesis that under the expected higher variability owing to global climate change, the months with the highest contributions to the interannual variability of $P$, $\mathit{ET}$, and $T_{\mathrm{air}}$ in the MRB will remain unchanged and quantified likely temporal trends in these quantities. Using high-resolution, downscaled Coupled Model Intercomparison Project Phase 5 multi-model ensemble data sets, we compared the multi-year ratio of monthly and annual interannual variability and temporal trends in $P$, $\mathit{ET}$, and $T_{\mathrm{air}}$ during 2011–2020 with three future decades. Results showed that the 6 months with the highest interannual variability in $P$ and $\mathit{ET}$ (April–September) are the same in all four decades. However, for $T_{\mathrm{air}}$, only 4 months (December–March) retain their status as highly variable throughout the four decades; September and October variability is exceeded by the variability in other months. This implies that, compared to $P$ and $\mathit{ET}$, the cyclical change in the probabilities of $T_{\mathrm{air}}$ in the MRB is less stable under future global climate change. This finding can be used to consider the need to alter existing strategies for reservoir release while minimizing the likelihood of aggravating flooding below the reservoirs.     

Leachate generation and biogas energy recovery in the Jebel Chakir municipal solid waste landfill,Tunisia

A survey was conducted between 2006 and 2008 in order to identify municipal solid waste (MSW) composition and its influence on leachate generation and to assess the amount of biogas yield from the Jebel Chakir landfill in Tunis City. The organic fraction was the predominant compound in the MSW, followed by paper, fine, plastic, leather, rubber, metal, textile, glass and ceramic. The average MSW moisture content varies from 60 % in the wet season to 80 % in the dry one. The recognised MSW composition is well representative if compared to that of cities in developing countries. A large leachate quantity is produced in the landfill of Jebel Chakir, despite the negative water balance of the site. Based on the annual MSW landfilled quantities and using the LandGEM model, the expected peak landfill gas (LFG) production is estimated to occur 1 year after the landfill closure with a rate of 3.53 × 10⁷ m³/year. The analysis of the potential conversion of LFG to electric energy shows it at a total LFG-to-electricity energy of around 257 GWh with a heating value of 4,475 kcal/m³ based on an LFG collection efficiency of 33 % and energy efficiency of 33 % giving an economic feasibility for a 10 MW power plant.     

Distribution and fractionation of cadmium, copper, lead, nickel, and zinc in a calcareous sandy soil receiving municipal solid waste

This study was conducted to evaluate the degree of mobility and fractionation of cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn) after the addition of municipal solid sewage sludge (MSS) in a sandy calcareous soil. Treatments were (1) soil application of MSS, (2) soil application of enriched municipal solid waste compost (EMSS), and (3) control soil. The MSS application represented a dose of 200 Mg dry weight per hectare. Soil columns were incubated at room temperature for 15 days and irrigated daily with deionized water to make a total of 505 mm. At the end of leaching experiments, soil samples from each column were divided into 14 layers, each being 1 cm down to 10 and 2.5 cm below that and analyzed for diethylenetriaminepentaacetic acid (DTPA)-extractable Cd, Cu, Pb, Ni, and Zn. The fractionation of the heavy metals in the top five layers of the surface soil samples was investigated by the sequential extraction method. All soil layers of the columns receiving MSS and EMSS had significantly higher concentrations of DTPA-extractable heavy metals than control soil. The maximum concentration of heavy metals in treated soil was in the surface layer and declined significantly with depth. Sequential extraction results showed that in the treated soil, a major proportion of Cd, Pb, and Ni was associated with organic matter (OM) and exchangeable (EXCH) fractions, and a major proportion of Cu and Zn was associated with residual (RES) and OM fractions. Based on relative percent, Pb, Cd, and Ni in the EXCH fraction was higher than Cu and Zn in soil leached with MSS and EMSS, suggesting that application of this MSS to a sandy calcareous soil, at the loading rate used here, may pose a risk in terms of groundwater contamination with Pb, Cd, and Ni.     

Modified dehydrogenase enzyme assay for evaluation of the influence of Hg,Cd, and Zn on the bacterial community structure of a wastewater treatment plant

In this study, a traditional assay was modified to evaluate the effect of Hg, Cd, and Zn on the bacterial community of a sequencing batch reactor and activated sludge plants and heavy metal-resistant bacterial species were determined. After the isolation of metal-resistant bacteria, their 16S rRNA gene fragments were sequenced. The BLAST program was used to compare the resulting 16S rRNA sequences with those in GenBank database to identify the isolated bacterial species. Hg was found to be the most toxic metal for both bacterial communities investigated. Sequence batch reactor bacteria were comparatively more resistant to Hg, Cd, and Zn than those from activated sludge. The resistant strains were close to the members of genus Pseudomonas, Kocuria, Stenotrophomonas, Enterococcus, and Staphylococcus. The modified dehydrogenase enzyme assay seems to be simple, robust, and competent for evaluation of the impact of metals on bacterial activity. Sequencing batch reactor systems should be preferred over activated sludge when wastewaters containing hazardous metals are to be treated.     

HYDRODYNAMIC MODELS OF HUMAN STABILITY IN A FLOOD1

ABSTRACT: Major loss of life can occur in a flood when people are toppled by floodwater currents. Three approximate mechanical models and two empirical models of the hydrodynamics of toppling are presented and calibrated to align with available experimental observations to assist the analysis of the risk of life loss. The mechanical models consider circular cylindrical, square cylindrical and cylindrical composite, heavy bodies assembled to represent a human immersed in a flow field and subject to drag and buoyancy forces. The models can account for the height and weight of the exposed persons, and the velocity and depth of the flow. The models are in good mutual agreement and, when calibrated, yield failure functions that can be used to calculate the probability of loss of stability.