Journal of Air Pollution and Health

51-60

Authors: Kazem Naddafi, Alireza Mesdaghinia, Mehrnoosh Abtahi, Kamyar Yaghmaeian, Ramin Nabizadeh, Nematollah Jaafarzadeh, Noushin Rastkari, Reza Saeedi, Shahrokh Nazmara

Introduction: Dichloromethane (DCM) is an air pollutant emitted mainly through industrial application. In this study, removal of DCM from waste gas streams using a pilot-scale hybrid bubble column/biofilter (HBCB) bioreactor was studied in steady state. Materials and methods: The hybrid bioreactor had two compartments: bubble column bioreactor and biofilter.The experiments were carried out with relatively constant concentration of DCM (approximately 240 ppm) and variable empty bed residence time (EBRT) of 50, 100, 150 and 200 s in steady state. Results: The average DCM removal efficiency of the HBCB bioreactor at EBRT of 200 and 150 s were 79 and 71%, respectively, but further reduction of EBRT significantly decreased the DCM removal efficiency. DCM removal rate was determined to be in the range of 12.1 g/m3.h to 19.6 g/m3.h. The first order rate equation best described the kinetic data of biofiltration (R2>0.99) with kinetic constant of 0.0114 1/s. The mixed liquor characterization indicated that the daily adjustment of pH and EC was sufficient to prevent any limitation in the performance of the HBCB bioreactor. Conclusions: This study showed that the HBCB bioreactor could be an efficient, economical and flexible option for DCM removal from waste gas streams.

69-76

Authors: Amirreza Talaiekhozani, Mohammad Reza Talaie, Mohamad Ali Fulazzaky

Introduction: Formaldehyde is a toxic, mutagen and teratogen chemical, and it is suspected to be carcinogenic to humans. As a result, it can be classified as a noxious air pollutant which must be removed from any formaldehyde-contaminated air stream before releasing to the atmosphere. Biological methods, particularly biotrickling filtration, have recently attracted a great deal of attention due to low operating cost and high removal efficiency. Materials and Methods: In this study, the biotrickling filtration of air stream contaminated by formaldehyde was investigated in a continuous system. The main objective of this study was to investigate formaldehyde biotrickling processes in continuous mode, culminating in the development of a mathematical relation to correlate volumetric mass transfer coefficient versus the Reynolds number of gas flow. During these experiments, formaldehyde removal efficiencies of 97, 97.5 and 96.5% were achieved for the gas flow rates of 90, 291 and 1512 l/h, respectively. Biotrickling filter reactor (BTFR) was employed for this continuous experiment. Results: The results obtained in this study show that the mass transfer from gas phase to the gas-wet biomass interphase is the controlling step, and the reaction rate is not an important factor in this case for a wide range of gas flow rates and gas velocities. Conclusions: The analyses demonstrate that external mass transfer is the controlling step compared to diffusion through liquid phase and bio-reactions. The results also show that using smaller but longer beds resulting in higher velocities enhances the mass transfer rate and hence the removal efficiency.

83-98

Authors: Foroogh Shadman, Khalid Abdul Rahim

Introduction: One of the largest proportions of human-related air pollution is produced by fossil-fuel based electricity generation units. Hence, the environmental performance that complies with technical performance receives increasing attention and seems to be the missing point in environmental impact analysis and energy policy studies. Therefore, empirical analysis which leads to increasing awareness of official policy makers concerning the technical and environmental trade-offs is the objective of the study in the electric generating sector by applying a two-stage Data Envelopment Analysis (DEA). Materials and Methods: In the first stage the DEA incorporates Materials Balanced Principle (DEA-MBP) to estimate the allocation of gas, mazut and gas oil of steam plants to minimize inputs and SO2 emissions respectively with the given technology. It is then followed by applying Ordinary Least Squares (OLS) applied in the second stage investigate the other explanatory variables which may influence the efficiency and were not properly considered in the first stage analysis. Results: The results evident that there is considerable gap between technical and environmental efficiency (76% and 10% respectively) scores. The impact of most important explanatory variables in the second stage clearly demonstrates that plant sizes and fuel type have significant influence while plant age and the year of observation have no statistically significant influence on the technical and also environmental efficiencies of steam power plants. Conclusions: Advancement in interdisciplinary research helps to increase technical efficiency while reducing emissions by applying analytical methods, which may provide better information for decision making units. Hence, it is the management’s responsibility to improve efficiency by modifying regulation and competition performance in this respect.

111-122

Authors: Amirreza Talaiekhozani, Marzieh Bagheri, Najme Rostami Najafabadi, Elham Borna

Introduction: Now, 100% of solid waste in Najafabad is recycled. The main aim of this study is to evaluate the effect of 100% solid waste recycling on emissions of CO2, CH4 and more than 40 non-methane organic compounds from landfill to the atmosphere. Materials and methods: To achieve this aim, it is assumed that if 100% solid waste recycling were not carried out in Najafabad, and if this city had a landfill with enough capacity to accept its solid waste for 20 years, a significant amount of the mentioned gases would have been emitted into the atmosphere. With this assumption, all necessary information about the amount of solid waste production in Najafabad was collected and the amount of gases released into the atmosphere was calculated by LandGEM software. Results: The results show that for landfilling of Najafabad solid waste over 20 years, a landfill with capacity of 2.3 million m3 is needed. Total generated CO2 and CH4 from this imaginary landfill during 20 years of fictional landfill operation are 107206 and 39074 tons, respectively. In addition, considerable amounts of CH4 and CO2 emission would continue for an estimated 120 years after landfill closure year. Calculations show that in 2015 alone, 93.79 tons of hazardous non-methane organic compounds could have been emitted into the atmosphere, most of them toxic and carcinogenic. Conclusions: Today’s 100% solid waste recycling in Najafabad has completely avoided these emissions. Consequently, it is recommended that nearly 100% solid waste recycling must become the final goal in all Iranian recycling organizations, to decrease landfill costs and to realize a healthier environment.

137-152

Authors: Shahram Nazari, Majid Kermani, Mehdi Fazlzadeh, Soodabeh Alizadeh-Matboo, Ahmad Reza Yari

Dust storms can cause certain environmental impacts such as reducing solar radiations, geochemical and biogeochemical effects, affecting marine primary producers or autotrophs, (thus reducing the disposal of carbon dioxide and global warming), affecting snow’s Albedo. One reason why dust causes such global effects is its transferability range up to 20,000 km. Dust can also negatively affect the respiratory, cardiovascular, cerebral-vascular systems; cause or intensify meningitis, fever, pain, allergies, and viral infections; damage the DNA of skin and lung cells. The Sahara and West China are known as the primary sources of dust worldwide. The most important methods of dust storm prevention and controling it can be biological, sprays (water), mechanical, chemical, and engineering. Biological methods are the best-known ways of preventing dust storms and desertification. This can be achieved by creating vegetation and ecological barriers, such as forest belts. Considering the increasing number and periods of dust storms and dust effects on the environment and human health, this review article aims to determine appropriate strategies to prevent dust occurrence and explain the effects of dust on health and the environment.