Current Issue : January-March Volume : 2022 Issue Number : 1 Articles : 5 Articles
Combustion in fluidised bed boilers is one of the most commonly used methods of treatment of municipal sewage sludge. Fly ash (FA) and air pollution control (APC) residues are the solid by-products generated by flue gas treatment. There are significant differences in the chemical composition of these wastes. FA is composed of mainly SiO2, P2O5, CaO and metals such as Zn, Ti, Cu, Cr, Pb and Ni. APC residues mainly contain SO3 and Na2O. The leachability tests that were carried out indicate that these wastes display very low leachability of heavy metals (for example leachability of Pb was equal 0.0004 mgdm3 in both wastes, leachability of Cd was equal 0.0012 mgdm3 in FA an 0.00004 mgdm3 in APC). On the other hand, very high sulphate concentrations (49,375 mgdm3) were found in water extract for the APC residues. In order to determine the toxicity of these wastes for plants, pot experiments with different additions of waste to the soil were carried out (on Lepidium sativum and Sinapis alba). Tests based on seeds germinations (on Lepidium sativum) in water extracts from waste (in different concentrations) were also performed. The results obtained indicate the very high toxicity of APC residues. Complete inhibition of germination and growth of the test plants was found for all concentrations of the tested waste in water extract and for all additions of waste to the soil in pot experiments. Seed germination tests on water extracts from FA did not show any toxicity of this waste. Pot tests with FA showed their toxicity only with a high (30%) addition in soil....
Rural communities in sub-Saharan Africa (SSA) are always faced with the challenge of securing safe water for beneficial uses. Most communities lack a centralized water supply system and, thus, each residence utilizes the treatment method that they can afford. This study evaluated three treatment methods for drinking water in the Njala University and Mokonde communities in southern Sierra Leone. In the perceived natural treatment, residents in the Mokonde community believe that groundwater has been purified by the soil media and, hence, does not require further treatment. In the conventional treatment, the Njala University Water Works use sand filtration and chlorine disinfection to treat water from the Taia River. The third treatment method, first flush diversion, was introduced by Njala University researchers in 2014. We studied the populations of coliform bacteria and E. coli in untreated and treated water samples to determine if each of the treatment methods supported the beneficial use of drinking. This study concludes that the natural filtration does not remove pathogens in the well water. Even though the first flush and conventional treatments were efficient in reducing microbial populations in the water, the World Health Organization’s 100% removal guideline was not achieved most of the time. Therefore, all three treatment methods did not support the beneficial use of drinking. Further treatment was needed to render the water potable....
The problem of water scarcity and salinity in North Africa is one of the main important constraints to any development. Libya is considered a Saharan country more than 90% of its area. Average annual rain is about 100 mm while evapotranspiration is more than 2000 mm. The Al-Hira study area belongs to the Al Djfara plain in north-western Libya, which is one of the most important pastoral areas of the region and it was until the 90s considered a good grazing area. The study area covers an area of approximately 269,938 hectares. The study carried out in the Al Hira area belonging to the Djfara plain showed an advanced state of degradation of natural resources: 1) decrease in irrigated areas and shrub vegetation; 2) increase in bare land areas; 3) fair water management (poor irrigation uniformity, bad irrigation scheduling). The irrigated areas were decreased from 18,000 to 12,000 ha between 1996 and 2008; an increase in bare soil was observed (23,000 ha to about 35,000 ha) between 1988 and 2009. The uniformity of localized irrigation under olive trees is often less than 50%, indicating the need to replace all the irrigation networks. In the case of sprinkler irrigation, irrigation equipment appears to meet the standards but the uniformity coefficient obtained at field level is very low (63%). The study on natural resources management in this area is imperative. Also an integrated water resources scheme is necessary for a better use of transferred saline water and aquifer fresh water....
The presence of potentially toxic metals in water causes a strong impact on environment and human health. In this study, activated biochar was produced by using chemical oxidation method from wheat straw as natural adsorbent and was employed for heavy metals competitive remediation. The morphology, structure, and chemical properties of biochar before and after adsorption were characterized by FTIR, XRD, SEM and EDX mapping techniques. The competitive adsorption efficiency of adsorbent for divalent cadmium (Cd) and lead (Pb) from contaminated water was investigated by using wide range of several initial metal concentration, contact time and pH. Maximum adsorption of Cd(II) and Pb(II) was found in the pH range of 6–8. The adsorption capacity for Cd(II) and Pb(II) was 8.85 and 9.03 mg/g, respectively. Thermodynamics parameters and kinetic models were applied to adsorption data. The isotherm data followed Langmuir model, corresponding to monolayer adsorption of the two ions in the contaminated water. The kinetic data followed the pseudo 2nd order kinetics model, which authenticates the chemisorption nature. The thermodynamic study indicated that Cd adsorption is a spontaneous exothermic process while Pb adsorption is an endothermic process. ...............
Dabus sub-basin is one of the main tributaries of Blue Nile with a considerable surface water potential which can be used for hydro power, irrigation, and water supply. Lack of studies regarding surface water potential and demands at the sub-basin level is the reason why this potential was underutilized. The objective of this study is to assess the surface water potential and evaluate the current and future demand by using Water Evaluation and Planning (WEAP) model at Dabus sub-basin. The model was constructed on four different scenarios starting from the current account (2020) wherein all the data is filled into the model to estimate the surface water potential and demands for different sectors. The scenarios include Scenario 1: reference scenario; Scenario 2: Change in population growth rate; Scenario 3: Irrigation water demand projection; and Scenario 4: Increased domestic water demand. The scenario has helped in analyzing “what if” questions. For all the scenarios the overall demand, coverage and unmet demand were analyzed based on three-time horizon as (2020-2030, 2030-2040, and 2040-2050). The model estimated the average annual flow as 6.536 Billion Cubic Meter (BCM) which is generated from annual precipitation of 14.987 BCM. The model showed 100% demand coverage for all the scenarios except the irrigation demand projection scenario which have unmet demand on some of the months of the year....
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