Simulation of Odor Transport and Dispersion from a Waste Water Treatment Plant: A case study of Kahawa Ward Nairobi County

Wacuka Cynthia Nyambura*, Nzioka John  Muthama**, John Kinyuru Ng’ang’a*and Bethwel Kipkoech Mutai*

*Department of Meteorology, University of Nairobi, P.O. Box 30197-00100, Nairobi

**Wangari Maathai Institute for Peace and Environmental Studies, P. O. Box 29053-00625, Nairobi

https://doi.org/10.20987/jccs.1.09.2017

Corresponding Author

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(Received 23September 2016, received in revised form 6 March 2017, Accepted 31 August 2017)

Abstract

Increasing evidence alludes that the developing countries are slowly losing their natural beauty and a clean environment to the different forms of hazardous waste among them waste water pollution. Waste water treatment plants emit odor that is considered a significant source of environmental pollution in Kenya. This is a crucial issue owing to the potential health impacts on the surrounding population and its significance to climate change. In this study, the seasonal distribution of odor was analyzed by use of Hybrid Single Particle Lagrangian Integrated Trajectories (HYSPLIT) and dispersion analysis. The study utilized archived meteorological data (daily wind speed and direction, temperature and humidity) as model input. Time series analysis was used to determine the temporal evolution of boundary layer depth, vertical mixing coefficient and atmospheric stability. Moreover, Computed odor concentration levels were compared to the national ambient air quality standards as a measure of possible health and environmental effects. The results showed that the predominant wind directions were easterly and south easterly with odor concentration reducing away from the source due to the resultant atmospheric dilution. Similarly, odor concentration depicted seasonal variations with the highest concentration levels being recorded during December January February season, while September October November season had the least values of odor concentration. Moderate odor concentration levels were observed during the March April May and June July August seasons. In conclusion, the variation of wind speed and direction influences depth of the boundary layer, vertical mixing coefficient and atmospheric stability. This in turn influences the transport and dispersion of odor. The findings from the study will prove useful in predicting odor occurrences in the area of study and hence develop solutions for effective management of wastewater plants.

Keywords:  odor,  wastewater  treatment  plants,  mixing  coefficient,  boundary  layer  depth, atmospheric stability

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Influence of Urbanisation on Minimum and Maximum Temperature characteristics over Nairobi City

Ndolo Isaac John * , Nzioka John Muthama ** , Christopher Oludhe *** , John Kinyuru Ng’ang’a *** and Richard S. Odingo *

*Department of Geography and Environmental Studies, University of Nairobi

**Wangari Maathai Institute for Peace and Environmental Studies, University of Nairobi

***Department of Meteorology, University of Nairobi

https://doi.org/10.20987/jccs.1.04.2018

Corresponding Author

Ndolo Isaac John

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(Received 4 August 2017, received in revised form 7 December 2017, Accepted 11 April 2018)

Abstract

Urban Heat Island being the most investigated aspect of urban climate is not prominently investigated in tropical African urban areas. This paper seeks to address the influence of urbanization on outdoor temperature characteristics in the city of Nairobi. Monthly minimum and maximum temperature data from four ground based weather stations namely, Dagoretti Corner (DC), Wilson Airport (WA), Jomo Kenyatta International Airport (JKIA) and Moi Air Base (MAB) stations over a 47 year period from 1961 to 2007 were used. The data were subjected to time series analysis. Station to station correlation analysis was performed as an indicator of the linear association of station records and also to understand spatial variability. Spatial analysis of temperature across the city pointed out that the most representative station in studying the urban canopy characteristics of the city of Nairobi is MAB. The minimum temperature across the city shows a significant positive trend. This may be attributed to urbanization effect. Among all the four stations, only DC exhibited a significant positive trend of maximum temperature. Trend analysis revealed that there was significant minimum temperature increase of 0.430C with a significant maximum temperature increase of 0.11C per decade during the 47 year period. This is a strong evidence of temperature modification due to urbanization. Comparative analysis of temperatures across the city of Nairobi depict heterogeneity among the four weather stations, with MAB being the hottest while DC is the coldest. Therefore, the microclimate of Nairobi is not homogeneous and implications of urbanization on planning of climate sensitive structures and services should be area specific. Further analysis to establish Urban Heat Island (UHI) characteristics of the city in future is recommended especially with availability of more weather stations around the city of Nairobi and adjacent rural areas.

Keywords: UHI, Minimum and Maximum temperature, Trend

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Assessing the Vulnerability of the Residents of Rachuonyo North Sub-County to Climate Variability and Climate Change

Opere Jasmine Evelyn Ajwang, Francis Mutua, and John Kinyuru Ng’ang’a

Department of Meteorology, University of Nairobi, P.O. Box 30197—00100, Nairobi (Kenya)

https://doi.org/10.20987/jccs.2.08.2017

Corresponding Author

Address: P.O. Box 15160—00100 Nairobi

E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

(Received 11 November 2016, received in revised form 3 July 2017, Accepted 2 August 2017)

 Abstract

Climate change is already impacting communities at household level. The analyses of the risks and vulnerabilities of the people living in a given area are important to understanding the impacts of climate variability and change in that given location. This Research perceived vulnerability as level of exposure by residents of Rachuonyo North Sub-County to socio-economic and climate risk and made attempts to empirically assess household vulnerability. Vulnerability Index (VI), calculated and normalized using United Nations Development Programme (UNDP,2009) vulnerability normalization method, estimates revealed higher vulnerability in Central Karachuonyo Ward followed by North Karachuonyo, Wang’chieng, Rambira and Kendu Town wards respectively. Vulnerability Index has an advantage of serving as a measurement metric for exposure of a population to socio-economic and climate risk. However, the use of Vulnerability Index may give misleading results if the functional relationship is not taken into account during the normalization process. From the results it is recommended that vulnerability assessment and mapping of Vulnerability Index over the whole County be undertaken.

KEYWORDS: Climate Change, Vulnerability Index, Rachuonyo North Sub-County

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