| Summary: | Landfill sites that are situated near residential zones pose significant management
challenges. One of the key issues concerns odour emissions; they can be a major cause
of public opposition to the existence of landfills. Mounting opposition can result in costly
and premature closure of waste management facilities.
The Bisasar Road landfill in Durban is one of the largest general waste landfills in South
Africa, and is surrounded by residential areas on three sides. Odour emissions are
therefore of primary concern. The situation at Bisasar provided an opportunity to involve
the surrounding residents as odour "receptors" in order to undertake research that would
provide a better understanding of odour emissions and how best to manage them.
Effective management of odour emissions requires a model to accurately predict the
occurrence and extent of the problem. For effective modelling and prediction of odour at a
landfill, it becomes necessary to characterize the odour sources in terms of their odour
emission rates and also to establish the population's response to the odour over a wide
range of concentrations. This thesis describes the application of numerical dispersion
modelling, coupled with interactive community involvement, in order to indirectly estimate
odour emission rates, where the community acts as an odour assessment panel.
A reanalysis of data captured from a 2002 community survey was performed in order to
investigate the odour emission rate from the open waste piles - transfer station and
working face - at the Bisasar road Landfill site. The odour emission rate from these similar
odour sources was found to lie in the range 102-103 OU/m2/s. For the duration of the
survey, the working face contributed 82% to the odour perceived at the receptors and the
Transfer Station contributed 18% to the overall offsite odour. The 2002 survey required
receptors to fill out a weekly diary of odour observations, but a new community survey in
2004 used direct telephonic communication with receptors to establish the odour impact.
Residents were contacted telephonically at their homes on a regular basis to ascertain
whether they perceived an odour at the time of call. This data, in conjunction with the
concentration predictions form the odour prediction model, allowed for an emission rate for
the open waste piles to be inferred through backward dispersion. The emission rate from
an open waste pile was estimated at being 250 OU/m2/s. The individual response of each
receptor as well as the combined response for the panel to a range of odour
concentrations was assessed in terms of probability of detection and perceived odour
intensity.
The odour emission rate, inferred through backward dispersion using the 2004 community
survey data, was used to establish the impact of the odour from the open waste piles on
the surrounding community through long term forward dispersion calculations. This
provided a scientifically defensible methodology for the specification of
buffer zones around sources that emit nuisance odours. === Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.
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