Spatiotemporal analysis of droughts using self-calibrating Palmer’s Drought Severity Index in the central region of South Africa   总被引：1，自引：0，他引：1  

Desalegn C. Edossa  Yali E. Woyessa  Worku A. Welderufael 《Theoretical and Applied Climatology》2016,126(3-4):643-657

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Anaerobic co-digestion of sanitary wastewater and kitchen solid waste for biogas and fertilizer production under ambient temperature: waste generated from condominium house     

M. Minale  T. Worku 《International Journal of Environmental Science and Technology》2014,11(2):509-516

Addis Ababa is one of the fastest growing cities where high urbanization has become a challenge. Consequently, housing shortage is a big problem of the city. The municipality has launched a huge Condominium Housing Programme in response to the problem. However, sanitary wastewater and solid waste management are the critical problems to those houses. The wastes were collected and evaluated for its biogas production and fertilizer potential to solve the foreseen waste management problems. The physicochemical characteristics of the collected wastes were determined. A laboratory scale batch anaerobic co-digestion of both wastes with different mix ratio of 100:0, 75:25, 50:50, 25:75, and 0:100 by volume [sanitary wastewater (TS = 7,068 mg/L):kitchen organic solid waste (TS = 56, 084 mg/L)]were carried out at ambient temperature for 30 days. The amount of biogas and methane produced over the digestion period for those mixing ratios were compared. The highest biogas yield obtained from a mix ratio of 25:75 was 65.6 L, and the lowest from a mix ratio of 100:0 was 9.5 L. The percentage of methane gas in the biogas was between 19.8 and 52.8 %. From the study results, it is evidenced that the mixing ratio 25:75 produced the maximum quantity of biogas and methane. With regard to the fertilizer potential of the digested sludge, composting and sun drying process were helpful for land application by inactivating the pathogen.  相似文献   

Urban flood vulnerability assessments: the case of Dire Dawa city,Ethiopia     

Erena  Sitotaw Haile  Worku  Hailu 《Natural Hazards》2019,97(2):495-516

Dire Dawa city is identified as one of the most flood-affected cities in Ethiopia. Classifying village-level flood vulnerability using flood indicators is a new approach to Dire Dawa city. Analysis of different flood vulnerability factors underpins sustainable flood risk management and the application of Flood Vulnerability Index (FVI) approach is the hub of this study. Relevant data were collected from 110 households sampled from purposely selected 10 villages found in Dire Dawa city. The flood vulnerability index was used to compare, classify and rank villages in terms of their flood vulnerability levels. For this purpose, 24 sets of indicators which are strongly affecting the levels of flood vulnerability were assessed from social, economic and physical perspectives. The FVI of each village was computed with unequal method of weighting indicators. The findings of the study revealed that Dire Dawa city villages were experiencing varying levels of flood vulnerability. Accordingly, villages 05, 06, 07 and 09 were identified with high flood vulnerability level while villages 03, 04 and 08 and villages 01, 02 and extension village were identified with medium and low level of vulnerability, respectively. Interestingly, the findings of the study confirmed that social factors contributed much for flood vulnerability in Dire Dawa city. Hence, future urban flood risk planning and management endeavors in the city of Dire Dawa must be underpinned by proper utilization of the flood vulnerability map developed addressing social vulnerability component through both structural and non-structural urban flood risk management measures.

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