Odour exposure level measurement surrounding palm oil mill

Odorous gases such as ammonia and hydrogen sulphide produced by anaerobic bacteria are emitted when palm oil mill effluent (POME) is treated via anaerobic digestion. Although odour is a nuisance rather than a hazardous nature most of the times, sensory annoyance complaints provoke local authority to seek for feasible mitigation. Malaysian Department of Environment (DOE) under the jurisdiction of the Air Division has proposed an odour emission limit of 12 000 OUm–³ for palm oil mills recently. The objective of this article is to establish the anaerobic pond odour concentration at palm oil mill using open ponding system for POME treatment, identify ammonia (NH₃) and hydrogen sulphide (H₂S) gas content in odour sample collected from respective anaerobic pond, and establish the odour concentration (OUm–³) at residential locations close to a palm oil mill using open ponding system, covered lagoons and tank digester for POME treatment. The odour sampling and assessment were performed according to MS 1963:2007 Air Quality – determination of odour concentration by dynamic olfactometry with enhanced VDI3940 Grid Method. Results showed that odour concentration at source of anaerobic pond ranged from 44 135- 85 012 OUm–³ while H₂S content ranged from 15.9-103.9 ppm and NH₃ content ranged from 4.1-16.6 ppm. Odour concentrations at residential locations are often dominated by local odour sources such as chicken farms. Odour emission levels at all surveyed residential areas identified as palm oil mills origin were well below 10 OUm–³ most of the times although high level of up to 108.4 OUm–³ has been observed occasionally. Thus, the proposed odour limit value needs to be reviewed and justified based on further study with focus on more data collection, odour control guidelines, community odour impact survey, inclusion limit values for odorous chemical substances, odour regulation framework, odour assessment methods and odour management plan guidelines.