Volume 20 [2018]

Field experiments were carried out using Helianthus annuus in an attempt to improve the quality of soil conditions by application of industrial waste. A range of quantities of olive core, olive core ash and a mixture of the two kinds of waste were applied. In all experimental fields the plants reached their maximum height on the 80th day of their growth. The application of olive core increased the plant height and decreased the soil pH, suggesting an increase in the nutrient element bioavailability. There was also evidence that olive core increased the soil microbe biomass. Furthermore, olive core woodash gave the dry biomass of Helianthus annuus a boost.

Wind energy is a resource that does not require any fuel or feedstock to be treated, refined or transported. It does not produce air pollution and hazardous waste. Because of these, wind energy, one of the major renewable energy sources, has been widely used in recent years. In this work, a three-phase distribution static synchronous compensator (D-STATCOM) is demonstrated for power quality enhancement in wind energy distribution systems. A five-level cascaded inverter is used to implement the D-STATCOM. D-STATCOM is controlled to compensate the reactive power, balances the load and eliminate harmonics. A novel control algorithm is based on the indirect current control system with synchronous reference frame theory for generating the gating pulses of Voltage Source Inverter (VSI). This proposed control system has one model predictive controller and two modified fuzzy logic controllers. The performance of the three-phase D-STATCOM is validated for power quality enhancement with different loads through software implementation using Matlab/Simulink environment. The effectiveness of the proposed approach is verified through simulation studies.

Polycyclic aromatic hydrocarbons (PAHs) are a group of quotidian organic compounds having between two and six condensed aromatic rings braced in angular, cluster or linear forms possessing hydrogen and carbon atoms only. This work aims to evaluate the physicochemical characteristics of soil as determinants of PAHs distribution and fate. The study area is situated on the Benin River beneath the convergence of Jamieson River and River Ethiope. The weather and climatic conditions of the area are of the Niger Delta region. Sixteen priority PAHs were determined in ten sample stations. Upon extraction, purification and quantification of PAHs was done using GC-FID. According to the methods of Walkey-Blacks, Black and Bouyoucus, soil total organic carbon, pH and texture were analyzed respectively. Four replicate samples were chosen to create a composite and used as quality control. Kruskal-Wallis test with tied rank was used to determine a causative correlation between soil physicochemical parameters and ∑PAHs. Results showed that the study area is contaminated with high concentration of PAHs ranging from 60.76 – 271.11 239 µg.g-1 with higher percentages of HPAHs i.e. PAHs with LogKow > 4.0. It is observed that observed alkaline pH favour significant fungal, asperigellus and microbial degradation of PAHs, and hinder photo-catalytic degradation. However, acidification with elemental sulfur, ferrous sulfate and aluminum sulfate could enhance photo-catalytic degradation. Results of TOC and soil structure do not favour significant degradation of HPAHs. Kruskal-Wallis tied rank test revealed that there was a positive significant difference between pH, TOC, percentage clay, and silt fractions with ∑PAHs concentrations since calculated K is greater than critical K0.05, P<0.05 except percentage of sand fractions and ∑PAHs with P>0.05. A substantial percentage of these PAHs have no anthropic origin and are characterized as having high lipo-affinity, semi-volatility and resistance to biotic and/or abiotic transformations. Due to edaphic factors the observed HPAHs may partially degrade with the consequent formation of highly toxic by-products. Therefore, oral or dermal ingestion of soil in the study area may cause significant exposure of the human population to these PAHs. Risk assessment and probable toxicity effects on animal diversity should be carried out in soil samples of the study area.

Clay of the Middle Atlas Mountains region, Morocco, was used to investigate the removal of heavy metals ions (Cadmium and Copper) from aqueous solutions with respect to several experimental conditions including pH, contact time, initial solute concentrations, temperature and ionic strength. Kinetic study revealed that metal ions uptake was fast with 90% or more of the adsorption occurring within first 30 min of contact time. Adsorption rate increased with the increasing initial metal ions concentrations and the sorption rate was well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer.
The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir and Freundlich isotherm models. Equilibrium and kinetic adsorption data showed that clay displays a high selectivity with an affinity order of Cd > Cu. Thermodynamic parameters including the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes indicated that the present adsorption process was feasible and endothermic in the temperature range of 25–45 °C.