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