Iranica Journal of Energy & Environment
Volume:11 Issue: 2, Spring 2020

The soil in the Sangan iron-mining region in the east of Iran is contaminated with a high concentration of heavy metals, especially iron. The release of these pollutants into environment results in the transfer and accumulation of iron through the food chains, hence a reasonable solution is required to restore it. Bioaugmentation is an environmental friendly option to reduce the hazard effects of heavy metal in the contaminated soil. In this study, the consortia of two indigenous cyanobacteria isolated from soil of Sangan iron mining and used to bioremediate soil contaminated with iron, chromium, copper, lead, and nickel. The experiments were carried out by three treatment methods, including control soil, surface soil sprayed with cyanobacteria, and soil mixed with cyanobacteria for six months under laboratory condition. The scanning electron microscope showed the development of a network of filaments of the inoculated cyanobacteria (Oscillatoria sp. and Leptolyngbya sp.) with soil particles in both treatments. Bio-augmentation of the soil increased initial nitrogen content from 406 mg/kg in control to 664 mg/kg in soil mixed with cyanobacteria and 710 mg/kg in soil sprayed with cyanobacteria. Cyanobacteria inoculation decreased the available concentration of lead and nickel. The non-available heavy metal of soil in sample sprayed with cyanobacteria was in decreasing order: Cr > Fe > Ni > As > Pb > Cu. The maximum metal removal efficiency was 32%. In soil mixed with cyanobacteria increased in the root and hypocotyl lengths of radish and lettuce was observed compared to that in the control soil, indicated in the improvement of soil quality after bioremediation.

The design of a flat-plate solar collector (FPSC) is accomplished by multiple input multiple output (MIMO) design technique. The design variables (absorber, fluid and glass temperatures; length, width, height of the FPSC) were the unknown variables in the commensurate thermal balance equations based on; component, overall and yardstick thermal balance on the FPSC. Then, simulator matrices were setup comprising of coefficient and column matrices of design functions. The elements of the coefficient matrix were the partial derivatives of the design functions with respect to the design variables. Besides the convective and radiative heat transfer coefficients were function of the design variables. The initial values of the design variables (307K, 334.5K, 368K, 2 m, 1 m, and 0.045m, respectively) were set, at the seventh iteration, the output variables (306.9K, 339.15K, 368.1K, 2.01m, 1.005m, 0.04m, respectively) merged as the design functions ® 0 with insignificant change in the design variables. The output results were used to simulate FPSC, to track its responses to changes in the physical conditions, the stimulation revealed some constraints in the design of the FPSC, which is vital information for the overall optimization of the FPSC. The design yardsticks; the thermal efficiency (0.76) and the effectiveness (0.4) are quite pragmatic. This shows that MIMO technique to thermal system design is effective as convergence among the design variables was sought. Moreover, MIMO considered all thermal losses instead of basing the yardsticks on top loss overall transfer coefficient alone; thus, neglecting sidewalls and base losses. Moreover, the advent of connecting box prepares the preheating unit for high temperature drying (> 150 oC) on integration with a reheating unit.

The main aim of this study is to use waste heat for cooling effect production from cement rotary kiln shell by applying vapor absorption refrigeration system. The plant has performance to manufacture 2000 tons of clinker per day. Energy and exergy analysis has been performed to assess first and second law efficiencies and rotary kiln is used as a control volume on dry type cement plant. Result shows that about 4.3MW energy is lost from kiln shell. From the analysis, 31.13% total exergy is wasted to the surrounding in case of pre-calcining and pre-heating of raw material. The overall result for exergy analysis of kiln indicates 59.46% of irreversibility and also the first and the second law efficiency of the rotary kiln is 53.39% and 40.54%, respectively. By using convective mode of heat transfer about 11% of energy is extracted by the generator for production of cooling effect which is wasted from kiln shell. About 300kW cooling effect is produced in the evaporator by applying absorption cycle with system performance 0.67 and exergetic efficiency 87%. From heat recovery there is direct savings by reducing fuel consumption and indirect savings by decreasing environmental impact. Hence, use of waste heat results in reduction of thermal pollution and energy consumption in auxiliary equipment.

Plantain stalks obtained from solid waste stream of Ganmo market in Ilorin was used in this study. Natural fibres extraction from waste plantain stalk was achieved using biological retting methods. The natural fibre was rented from the waste stalk after 24 days of soaking in water. The extracted fibres were exposed to 2, 4 and 6% alkali solution (NaOH) treatment for two hours, washed and dried in the oven for 7 hours. Elemental analysis of raw plantain fibres showed the presence of elements like Indium, Potassium, Silicon and Calcium among others. Tensile strength analysis of the fibres, for single fibre strands showed that the 2% treated fibre showed distinctly promising potential with the highest tensile characteristics of young modulus, stress at break and force at peak of 52864.366N/mm2, 5398.536N/mm2 and 2.650N, respectively. Evaluation of the chemical composition of plantain by FTIR spectroscopy indicated that treatment of natural fibres using NaOH beyond 2% have a negative impact on the plantain fibre properties. Through alkali exposure, the fibre configuration presents small variations in composition. It is consequently apparent that alkali treatment with concentration of less than 2% NaOH is sufficient to remove hemicelluloses and to obtain the optimum tensile effect.

The study was done to explore the production of charcoal briquettes that could meet the need for energy in the community of Jimma city. The primary objective of this work is to produce charcoal from the most promising wastes. Under these objectives the main activities which performed were sorting waste, characterization of wastes that can easily degradable, designing carbonizer equipment, manual press molding machine, and characterizing charcoal briquettes. Degradable municipal waste was collected from Jimma city. The charcoal production process includes a collection of degradable municipal waste, drying, carbonization, crushing and sieving, binder preparation, binder – charcoal mixing, briquette charcoal (compaction and drying), and packing. The test result of degradable municipal solid waste for its density, % of moisture, % of volatile matter, % of ash, % of fixed carbon, and caloric value of was determined as 157.3kg/m3, 18.15%, 66.95%, 4.07%, 10.83%, and 18.5MJ/kg, respectively. In the same way the test result for charcoal briquette for its density, porosity weight index, shatter resistance ,moisture content, volatile matter, ash content, fixed carbon content, and caloric value was obtained as 50.06kg/m3, 29.05%, 92.3 %, 9.87%, 29.4%, 3.21%, 57.52% and 27.0MJ/kg, respectively. These results show in the range compared with others reported in literature. Therefore, there is the possibility to convert Jimma City degradable solid wastes into charcoal briquette using starch as a binder. We can increase the quality of charcoal briquette rather than polluting the environment.

Ethiopia has a high potential for water for hydro-power development. Even though there is untapped potential, the country's electricity coverage is poor. This paper presents a technical-economic feasibility study of gunde micro hydropower at the Tindwat River, Central Gondar, Ethiopia. In the techno-economics study, the analysis was made for energy modeling, economic scenarios, and sensitivity, risk, and emission analyses. The study shows that this mini-hydropower project can be developed with an installed power of 18 kW, where the Kaplan turbine is recommended. The construction of small scale hydropower in the tindwat river is technically and economically feasible with total net present cost of US $ 253537, cost of energy $0.09/kWh, simple payback period of 6.9 years, and internal rate of return 23.9%. Te result also shows that construction of hydropower curtails greenhouse gas emissions of carbon dioxide by 588.65m3 of gasoil per year. It also showed that small hydroelectric power generation from Tindwat River would improve the electricity supply to Gunde Teklehaymanote monstery and off-grid rural communities.

Asphalt solar collectors (ASCs) offer a low-cost and reliable alternative to harvest energy from available infrastructures such as roads and pathways by employing the simple techniques. This paper represents an experimental study to evaluate the effectiveness of continuous and discontinuous-flow strategies in the dynamics and performance of a self-constructed ASC under field conditions. To this aim, an ON/OFF switching controller commands to run and stop the system at different time intervals. During the experimental simulations, all the crucial environmental and operational parameters were measured and monitored. This approach assesses the effects of numerous scenarios with different intervals of time on the dynamics of the constructed collector. Continuous and discontinuous-flow strategies were evaluated by comparing three different scenarios, including continuous-flow mode, 5 min OFF-mode and, 10 min OFF-mode. The results show that by extending the OFF-mode, the water is kept stagnant in the hot embedded pipes for more extended periods. Therefore, the temperature difference at the inlet and outlet of collector reduces, and the water leaves the collector at higher temperatures; however, the efficiency of the ASC decreases. Also, even though extending the OFF-mode results in heated water exits the collector at higher temperatures, but the mass of heated water decreases due to continuous interruption of current flow. The test results prove that in continuous-flow strategy, cumulative heat gain improves. Therefore, the continuous-flow strategy shows higher performance than introduced discontinuous-flow strategy. The exergy analysis illustrates that the available useful exergy has significantly affected by considering the pump consumed energy.

The assessment of environmental impact on concrete is an important aspect for its durability. The use of supplementary cementitious materials (SCMs) in the concrete can be enhanced the durability. This makes concrete sustainable and reduced environmental issues. In this research paper illustrate the experimental study on the performance of triple blend concrete made up of fly ash (FA) and rice husk ash (RHA) along with ordinary Portland cement (OPC). The current research the concrete composition was used as 20, 30 and 40% cement replacement by FA and RHA. The durability properties such as ultrasonic pulse velocity (UPV), electrical resistivity (ER), water absorption and carbonation depth of triple blend concrete were determined, and for microstructure performance formation factor and Scanning Electron Microscope (SEM) were performed. The improvement in durability was observed up to 40% replacement of cement. The durability of concrete improves with increase in formation factor. The SEM images proved the improvement in particle packing of concrete.

Due to high joint efficiency, welding is widely used to join materials. Today, there are many types of welding procedures in different manufacturing industries. Among welding procedures, Gas Metal Arc Welding (GMAW) is a versatile process due to its high flexibility. In this process, arc voltage, welding current, and welding speed are the main variables which can strongly affect the mechanical properties of the weld metal. Based on the available literature, many research works have been conducted on the GMAW process but there is still little experimental research on impact energy of the weld metal specifically in medium-carbon steels. Impact energy of the weld metal is extremely important particulary for the structures subjected to impact loads. Hence, the present paper is conducted to reveal the effect of GMAW variables on impact energy of the weld metal in CK45 carbon steel. The results of this paper indicated that the heat input value and weld bead size in different welding conditions are main factors which affect the impact energy of the weld metal.

Growth in population has caused a corresponding increase in agricultural production which consequently led to an increase in agricultural wastes or byproducts. This is sometimes difficult to manage and may pose a menace to the society if not properly disposed. Hence, this research investigated the efficacy of utilizing agricultural byproduct (melon husk) in removing Pb2+ and Cd2+ from wastewaters so as to prevent their deleterious impact on ecosystem and public health. This was achieved by treating tannery effluents with melon husks modified with H3PO4, NaOH and CH4N2O. Results showed that, the Freundlich and Langmuir adsorption capacities on the modified melon husks ranged from 0.1403 – 1.551 mg/g and 0.1499 – 0.6013 mg/g, respectively. Also, the R2 values for Pseudo 1st and 2nd order rate constants ranged from 0.0272 – 0.2391 and 0.9112 – 0.9958, respectively. Hence, it was concluded that the modified melon husks followed Freundlich isotherm model as well as Pseudo-2nd order kinetics and could be effectively used to remove Pb2+ and Cd2+ from wastewater.

Energy crisis and global warming have encouraged the use of renewable energy resources such as wind power. Among different types of wind turbines, vertical axis wind turbines can be easily installed in residential areas. In this study, a computational fluid dynamics analysis was performed to predict the performance characteristics of three configurations of small vertical axis wind turbines. For this purpose, an shear stress transport k-omega turbulent model and a rotating frame of reference were employed. Initially, a Savonius and a Darrieus wind turbine were simulated; the low power coefficient of the Savonius wind turbine and the poor performance of the Darrieus wind turbine in low tip speed ratios were the main disadvantages of these systems. Finally, a combined Savonius-Darrieus wind turbine was proposed to deal with these drawbacks. The power coefficient of this combined wind turbines was nearly as high as the Darrieus wind turbine (0.3), while the Savonius blades recover the low torque obtained at low tip speed ratios and help produce more consistent torque, making it suitable for residential applications.

The abilities of three indigenous bacteria for bioremediation of cadmium contaminated soils collected from Agbabu Farm Settlement close to mining sites in Ondo state, Nigeria was studied to provide helpful information for soils remediation and soils health management in this sub-region for Millennium Development Goals accomplishment. Bacillus subtilis, Proteus mirabilis, and Escherichia coli isolated from the soils were inoculated into different soil samples conditioned with optimized factors determined from the first phase experiments. The conditioned samples were experimented for residual cadmium concentration with time in days using Atomic Absorption Spectrophotometer. The soil cadmium attenuation from the initial concentration of 70.21 mg/kg to below the maximum allowable of 3 mg/kg was hard for the organisms. Bacillus subtilis performed correction at time 35 days with an efficiency of 96.10 % and residual concentration of 2.74 mg/kg. Proteus mirabilis and Escherichia coli with respective, high efficiencies of 85.05% and 79.35% failed. The removal rate capacities were -0.131d-1 for B. subtilis; -0.111d-1 for P. mirabilis; -0.105d-1 for E. coli. Four kinetic models fitted described the experimental data well. The models assessment revealed the removals to be transport controlled as diffusion process was the rate-controlling step.