Issue 3

This study explored the best-operating conditions for a novel electrocoagulation (EC) reactor with the rotating anode for textile wastewater treatment. The influence of operating parameters like inter-electrode distance (IED), current density (CD), temperature, pH, operating time (RT), and rotation speed on the removal efficiency of the contaminant was studied. A comparative study was done using conventional model with static electrodes in two phases under same textile wastewater The findings revealed that the optimal conditions for textile wastewater treatment were attained at RT = 10 min, CD = 4 mA/cm2, rotation speed = 150 rpm, temperature = 25oC, IED = 1cm, and pH = 4.57. The removal efficiencies of colour, biological oxygen demand (BOD), turbidity, chemical oxygen demand (COD), and total suspended solid (TSS) were 98.50%, 95.55%, 96%, 98% and 97.10% within the first 10 min of the reaction. The results of the experiment reveal that the newly designed reactor incorporated with cathode rings and rotated anode impellers provide a superior treatment efficiency within a short reaction time. The novel EC reactor with a rotating anode significantly enhanced textile wastewater treatment compared to the conventional model. The values of adsorption and passivation resistance validated the pollutants removal rate.

In this study, the potential use of Azolla filiculoides Lam. for the bioremediative solution to polycyclic aromatic hydrocarbon (PAH) pollution due to crude oil spills in freshwater was investigated. The plants were grown in nitrogen-free Hoagland nutrient solution media containing 0.05%, 0.1%, 0.2%, 0.3%, 0.4% and 0.5% crude oil by volume for 15 days under greenhouse conditions. Relative growth rates of A. filiculoides decreased in the presence of crude oil in a concentration-dependent manner. The probable influence of A. filiculoides on the biodegradation of polycyclic aromatic hydrocarbons was measured by using synchronous UV fluorescence spectroscopy. GC-MS analysis were also carried out to elucidate the behavior of the oil in experimental and control samples. Although 1-2 rings PAHs have not been encountered in control or plant samples, the measured intensity for 3-4 ring PAHs in plant samples was remarkably lower in comparison to the control. Furthermore, these results demonstrated that the predominant efficacy of the A. filiculoides was for 3-4 ring PAHs at the range 0.05 to 0.2% crude oil concentrations. It could be concluded that the bioremediative potential of A. filiculoides for the removal of polycyclic aromatic hydrocarbons strongly depends on the amount of oil in the contaminated water resource. In other words, A. filiculoides could be used more effectively after the removal of excess crude oil in the spilled freshwater areas.

The present study aims to investigate the human thermal stress with respect to the synoptic scale circulation over the metropolitan city of Athens in Greece. The Universal Thermal Climate Index (UTCI) was applied in order to assess the levels of thermal stress employing three-hour meteorological data for four stations of the urban complex for a ten-year period (2006-2015). The patterns of the synoptic atmospheric circulation were classified in eight distinct categories based on a clustering scheme. The obtained results in summer reveal low UTCI values on days that are associated with a cyclonic pattern or a cold advection from the northwest or north. On the contrary, the days with an anticyclonic pattern show high UTCI values. During winter, low UTCI values are observed on days that are associated with a pure cyclonic pattern, a prevailing northern flow and a strong cold air advection from the northwest or north. During nighttime, high UTCI values are noted on days with south-westerly flow. However, this is not observed during daytime and especially around midday. The analysis also shows that the position of the station affects the levels of thermal stress for the same synoptic category.

The mineral sequestration, one of the methods of CO2 sequestration, is considered advantageous, as it not only facilitates permanent and leakage free storage of CO2 but also obviates the need for regular monitoring. Mineral sequestration involves the dissolution of minerals and subsequently carbonation of dissolved minerals. In the direct mineral sequestration all the processes occur within a single reactor, whereas in the cases of indirect mineral sequestration, they take place in separate reactors. The main aim of the present study is to investigate the efficacy of these mineral sequestration methods and examine their suitability for industrial application and ensuring environmental friendliness. For this purpose, literature pertaining to these methods was extensively reviewed, and observations made by several researchers were collected, collated and compared based on the various parameters such as reaction pathways, reaction kinetics and cost of the process. The process cost was found to depend on the type of the process, process parameters, input materials and additives. It was noted that the direct mineral sequestration suffers from the sluggish reaction kinetics, thereby becomes economically unviable. The success of direct mineral sequestration process is yet to be achieved despite research carried out for several years. The problem of sluggish reaction kinetics was overcome by using multi-steps indirect carbonation routes, where separate reactors were used for dissolution and precipitation processes. The indirect sequestration method was noted to be most efficient as it offered several advantages such as improved reaction kinetics and recovery of the market value of by-product due to the better quality control of the product. Hence, based on interpretation of an extensive review of literature it can be concluded that the indirect mineral sequestration may be a viable option to carry out the CO2 sequestration and may be proved as a guiding light to ensure the clean environment for future generation.