| Title | Assessing the Odour Impact of Discharges to Air from the Tauhara Stage Two Geothermal Power Station |
|---|---|
| Authors | Mathew Noonan |
| Year | 2013 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | air pollution, hydrogen sulphide, odour assessment, geothermal power station emissions |
| Abstract | The Tauhara Stage Two project is a large geothermal power station to be located approximately 4.5km to the east of Taupo. Air discharges from the plant include water vapour discharged from the three wet mechanical draft cooling towers and non-condensable gases (NCG), which are vented above the above the cooling towers. From an air quality perspective, the primary concern is the potential odour nuisance effects associated with the discharge of hydrogen sulphide (H2S). However, unlike health impact assessments where there are usually clear air quality concentration criteria limits, the assessment of odour is complicated due to its subjective nature. Defining appropriate H2S odour criteria limits in geothermal area also need to account for existing H2S background levels. For this assessment, the relative effect of the plant was evaluated by comparing changes to the predicted frequency of an offensive or objectionable ‘odour event’ occurring at the nearby sensitive receptors with and without the project. Hourly average H2S concentrations for the area surrounding the plant were predicted using the CALPUFF atmospheric dispersion model and a time-varying three dimensional meteorological grid. The results of the dispersion modelling indicate that discharges from the proposed power station would be unlikely to result in a significant increase in the frequency or intensity of odour events at nearby sensitive receptors. The modelling also indicated that discharges of H2S and other contaminant were unlikely to have a significant health risk to surrounding community. |