Environmental damage of different waste treatment scenarios by considering avoided emissions based on system dynamics modeling

This study aims to develop a comprehensive model for life cycle assessment and environmental damage cost calculations considering avoided emissions in different waste management scenarios using the system dynamics (SD) approach. Our analysis reveals that under the business-as-usual (BAU) scenario for the period 2020–2050, the total net greenhouse gas (GHG) emissions reach 12.5 Mt, with the highest environmental damage cost being USD 689 million. In contrast, an integrated management strategy encompassing recycling, composting, anaerobic digestion, and incineration results in a 195% reduction in net GHG emissions compared to the BAU Scenario. Concurrently, the environmental damage cost drops to USD 277 million, incorporating USD 347 million in savings, leading to a net environmental damage cost of USD −71 million. The findings affirm that accounting for emissions avoided across various treatment methods offers a more accurate estimate of environmental damage costs. Additionally, policies centered on integrated waste management are more likely to achieve sustainability. The study also demonstrates the utility of the SD approach in providing a holistic view of waste management systems and in evaluating the effectiveness of various policy strategies for sustainable waste management

DEVELOPING A WATER QUALITY MANAGEMENT MODEL FOR KARUN AND DEZ RIVERS

The Karun and Dez rivers basin are the largest rivers basin in Iran which are situated in the south west of the country. Karun River originates from Zagros mountain ranges and passing through Khuzestan plain, reaches the Persian Gulf. Several cities lie along its path of them the most important is Ahvaz, the center of Khuzestan province. To achieve water quality goals in Karun and Dez rivers, a water quality management model has been developed through the GIS approach and a mathematical water quality model. In Karun and Dez rivers, water quality has decreased due to heavy pollution loads from Khuzestan province cities and surrounding areas. In this survey, pollution sources, land use, geographic features and measured water quality data of the river basin were incorporated into the Arc-view geographic information system database. With the database, the model calculated management type and cost for each management project in the river basin. Until now, river management policy for polluted rivers in Iran has been first of all to get penalties from pollution sources and secondarily, to construct treatment plants for the pollution sources whose wastewater is released untreated and for which the wastewater quality goal of the Iranian Department of the Environment is not met. Different management projects with a time program were proposed and they were compared with the results of the river quality without any management approach. It became clear that the results based on the management approach were much better than those for the unmanaged condition from the viewpoint of the achievement of water quality goals and cost optimization

Determination and health risk assessment of heavy metals (Pb, Cd, Cu and Zn) in different brands of pasteurized milk

The contamination of milk and its products with heavy metals has toxic and dangerous effects on human health. This study aimed to determine the heavy metal concentration and health risk assessment resulting from them in four different brands of Pasteurized milk consumed in Gorgan city, Iran. This study was performed during three seasons (summer, autumn and winter). Sixty different samples of pasteurized milk of four common brands were selected and analysed. Samples were digested in the laboratory by using nitric acid method digestion, and the heavy metal concentration was measured by using the linear regression based on the height of the peaks of the voltammograms. Also, health risk assessment was analysed by Oracle® Crystal Ball. According to the results, the overall mean (n = 60) concentration of Pb, Cd, Cu and Zn in all of the analysed milk samples was 0.02, 0.023, 0.97 and 4.31 µg/g, respectively. Based on these results, about 67 had Pb content lower than the codex limits, almost 70 of all milk samples had Cd content higher than the permissible limit, and Cu concentration in all milk samples was under the mentioned permissible limits. Zn concentrations in all samples were exceeded the permissible limits. HRI values in adults and children via consumption of pasteurized milk in all of the analysed samples were within the safe limits (HRI < 1). Based on these findings, monitoring of contaminants in milk and other dairy products prevented the probably side effects of these heavy metals on human health. © 2020 Informa UK Limited, trading as Taylor & Francis Group

Distribution trend of BTEX compounds in ambient air of urban solid waste landfill sites and surrounded environment: A case study on Ahvaz, Southwest of Iran

Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) are classified as hazardous air pollutants that have been identified at landfill sites and surrounding environments. Therefore, in the present study, BTEX concentrations were measured at new and old solid waste landfill sites of Ahvaz during cold and warm seasons. As one of the megacities in the southwest of Iran, Ahvaz produces more than 1,000 tons per day of solid waste. The produced solid waste is transported to the new Borumi landfill site, which is located at 31 degrees 17'28 '' N and 31 degrees 18'31 '' N latitude and 48 degrees 48'12 '' N and 48 degrees 50'15 '' longitude. Air samples were taken in both cold and warm seasons from 6 points including, one point in the new site, three points in the old site, a point between two sites, and one point in the city boundary (as background point). Air sampling was performed in the prevailing wind direction (the southeast wind), and the meteorological parameters, including temperature and relative humidity, were also measured during air sampling. The results showed that the emission rate of BTEX compounds in the old and new landfill sites of Ahvaz is considerable. So that, the highest concentrations in the old landfill site in the warm season for benzene, toluene, ethyl-benzene, and xylene were 173.82, 234.51, 246.18, and 20.84 ppm, respectively. However, these values in the cold season were 16.6, 50.04, 2, and 70.28 ppm, respectively. It shows that the concentration levels of BTEX were significantly higher in the warm season compared to the cold one

Efficiency of activated carbon produced by physical activation using nitrogen gas for maximum dye adsorption from polluted effluents: Genetic programming and neural network

Background and purpose: This study was conducted for the first time to produce activated carbon (AC) from Milkvetch wood by physical activation in order to achieve the maximum adsorbent capacity in adsorption of dye. The aim of this study was to remove acid orange 7 (AO7) dye using AC produced by physical activation with nitrogen gas. Materials and methods: AC activation was performed by physical method using nitrogen gas at 700°C. Scanning electron microscopy and isotherm technique were used to determine the structural characteristics of the adsorbent. The effect of operating parameters was investigated. The isotherms and kinetics of the dye adsorption were also studied. Results: The synthesized AC-700°C sample had a specific surface area and a total pore volume of 774 m2 /g and 181.49 m3/g, respectively. The maximum adsorption of dye was 57.125 mg/g (removal efficiency 91.4) that occurred at pH= 3, 0.04 g absorbent in 50 ml of solution, and 50 mg/l of dye in 75 min. The adsorption data followed the Langmuir adsorption isotherm model and the pseudo-second order model kinetics. Also, the ability to reuse the adsorbent using the heating method showed that the synthesized adsorbent can be used for three consecutive times with good performance. Correlation coefficients (R2) for genetic program and neural network were 0.98 and 0.99, respectively, indicating the agreement of laboratory data with the models. Conclusion: The as-prepared AC by physical activation has a high potential for adsorption of AO7 dye from aqueous solutions. © 2021, Mazandaran University of Medical Sciences. All rights reserved

Adsorption of Cr(VI) by Natural Clinoptilolite Zeolite from Aqueous Solutions: Isotherms and Kinetics

The main aim of this study was to evaluate the efficiency of natural zeolite for Cr(VI) removal from aqueous solutions. Following simple modification of adsorbent, the effect of operational parameters including pH (2–10), adsorbent dosage (2–20 g/L), contact time (5–150 min) and Cr(VI) concentration (10–50 mg/L) were studied according to one-factor-at-a-time procedure. The maximum Cr(VI) removal of 99.53% was obtained at initial pH of 2, contact time of 30 min, adsorbent dosage of 8 g/L and initial chromium concentration of 10 mg/L. The Freundlich isotherm was best fitted with experimental data (R2 = 0.951). Also, type 1pseudo second order kinetic model showed the most correlation (R2 = 1) with the experimental data. According to obtained results, it can be concluded that the application of clay-like adsorbents such as natural clinoptilolite zeolite can be considered as an efficient alternative for final treatment of effluents containing Cr(VI)

Optimization and genetic programming modeling of humic acid adsorption onto prepared activated carbon and modified by multi-wall carbon nanotubes

Milk vetch species (MV) as activated carbon (AC) precursors were prepared and modified by multi-wall carbon nanotubes (CNTs) in order to remove humic acid (HA) removal. Scanning electron microscopy (SEM), diffuse reflectance infrared Fourier transform spectroscopy (FTIR) and Brunauer Emmett Teller (BET) techniques were applied to characterized MVAC/CNTs. The HA adsorption presented the highest value (22.57 mg/g) at pH 3, while the equilibrium state was reached after 30 min. By increasing the adsorbent's dosage (0.4-0.5 g/L), the removal efficiency was also improved from 90.3 to 97.6. The kinetics of adsorption were fitted to the pseudo-second-order model (R-2 = 0.9991). The Langmuir isotherm model was well fitted to the equilibrium data revealing monolayer adsorption model of HA onto the MVAC/CNTs with the maximum capacity of 73.29 mg/g (R-2 = 0.9967). The obtained values of thermodynamic parameters indicated that the HA adsorption was spontaneous, endothermic and physical in nature. Also, genetic programming was used to obtain an appropriate equation revealing the relationship between the variables. The results showed that the introduced equation can successfully predict the HA removal. All experimental results suggested that MVAC/CNTs are promising adsorbents for the contaminated (with HA) water. (C) 2020 Published by Elsevier Ltd