Browsing by Author "Seleshi, Yilma"

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    Characterization of atmospheric bulk deposition: implications on the quality of rainwater harvesting systems in the semi-arid city of Mekelle, northern Ethiopia
    (Springer, 2016) Taffere, Getachew Redae; Beyene, Abebe; Vuai, Said A. H.; Gasana, Janvier; Seleshi, Yilma
    It is estimated that about 1.2 billion people, mostly in arid and semi-arid regions of the Middle East and Africa, live in regions where water is physically scarce. Recently, rainwater harvesting and more effective water storage are suggested as important means for investment to cope against water scarcity and as an adaption to climate change. Cognizant of this fact, contribution of atmospheric deposition contaminant to rainwater harvesting systems, in the semi-arid city of Mekelle was investigated at four locations (industrial, commercial, traffic and residential areas). A total of 24 bulk samples were collected during the rainy season from May to September 2014. Physicochemical water quality analysis was performed following standard protocols. The results revealed that alkaline pH (6.95–10.29) was recorded in all the locations, with a mean pH of 8.11. The major ions analysis indicated the dominance of bicarbonates and carbonate types and to some extent sulfate and chloride type mixtures justifying the source of alkaline pH. Mean concentrations of ions follow the order of SO4 2−> Ca2+ > Mg2+ > CI−> NO3 −> Na+ > NH4 + > K. Correlation between SO4 2− and NO3 − (r = 0.436), and Mg2+ and K+ (r = 0.707) suggested their anthropogenic and crustal origin, respectively, while the correlation between NH4 + with Ca2+ and Mg2+ ascribed their role in alkalization of the rainwater. Moreover, principal component analysis showed spatiotemporal variation of atmospheric bulk components in the study area. Thus, this primary investigation demonstrated that atmospheric bulk deposition might pose public health risk due to poor rainwater quality in Mekelle city. Therefore, development of rainwater harvesting systems for semi-arid urban centers should be supplemented with low-cost water treatment technologies.
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    Dilemma of roof rainwater quality: Applications of physical and organic treatment methods in a water scarce region of Mekelle, Ethiopia
    (Taylor & Francis, 2016) Taffere, Getachew Redae; Beyene, Abebe; Vuai, Said A. H.; Gasana, Janvier; Seleshi, Yilma
    The public health field has built a body of literature showing health benefits from improvements in water quality. However, the connection between roof harvested rainwater and health is not well documented especially in developing countries. Understanding the application of locally available treatment methods provides insight into this problem. This paper reports on experimental investigations where rainwater collected from a typical domestic roof in Mekelle, Ethiopia was treated using Moringa stenopetala seed, sand filter and boiling. The quality of the raw and treated roof harvested rainwater were compared against the Ethiopian and World Health Organization drinking water standards to investigate its suitability as a supplement for potable water supply. The pollutants analysed were total coliforms and turbidity. A significant improvement of turbidity and total coliforms was observed. This implies that application of plant coagulant followed by filtration can sufficiently treat rainwater and can be used as a low-cost treatment option in water scarce areas.
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    Location and time-specific investigation of roof rainwater quality is important to safeguard public health
    (Taylor & Francis, 2016) Taffere, Getachew Redae; Beyene, Abebe; Vuai, Said A. H.; Gasana, Janvier; Seleshi, Yilma
    Harvested roof rainwater plays a vital role in supplying water in the scarce semi-arid areas. Prior knowledge of rainwater quality helps to understand the relative pollutant contributions of location- and time-associated factors. The present work is aimed to explore source and time factors affecting rainwater quality and associated public health risk in the city of Mekelle, a semi-arid area in Ethiopia. Roof rainwater samples (n = 21) were collected from May to August 2014 from residential, commercial, bus station, and industrial areas. The samples were analyzed for major ions, physical parameters, and coliforms. The order of concentrations of major ions was observed to > Ca2+ > Cl− > Mg2+ > > Na+ > > > K+. The average pH of rainwater at these stations was 8.26 and ranging from 6.84 to 10.59, indicating alkaline nature. The observed alkalinity is attributed to the nature of soil and geological formation of the area and a significant influence of the cement factory. No definite trends were found in most of the ionic components at all the locations and time of sampling with p-value > 0.05. However, concentrations of physical parameters (total dissolved solids, electrical conductivity, total suspended solids, and turbidity) were statistically significant with time of sampling (p-value < 0.01). Bacteriologically, 76% of the samples were positive for total coliforms. Moreover, 19% of the samples were positive for fecal coliform. These signify the importance of appropriate treatment measures before using rainwater for domestic water supply so as to prevent potential adverse health effects.
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    Reliability analysis of roof rainwater harvesting systems in a semi-arid region of sub-Saharan Africa: Case study of Mekelle, Ethiopia
    (Taylor & Francis, 2016) Taffere, Getachew Redae; Beyene, Abebe; Vuai, Said A. H.; Gasana, Janvier; Seleshi, Yilma
    Curbing water scarcity problems in semi-arid regions is a top priority for economic and social development. Alternative strategies for sustainable domestic water supply are therefore required to augment water supply with affordable cost and technology. Scant research findings in sub-Saharan Africa have, however, reported inefficiency in adapting to water scarcity problems in the region. Therefore, an investigation of domestic rainwater harvesting (RWH) reliability is important to identify factors affecting the system. We found that rainwater harvesting with the existing traditional RWH systems in Mekelle city was unreliable. Unreliability was attributed to inefficient design (the systems were installed without considering deterministically the stochastic nature of rainfall), family size, water demand, rooftop area and storage tank size.