3.0 SOURCES OF ODOUR

Most commonly reported odour-producing compounds are hydrogen sulfide (rotten egg odour) and ammonia (sharp pungent odour). Carbon disulfide, mercaptans, product of decomposition of proteins (especially of animal origin) phenols and some petroleum hydrocarbons are other common odorants. Most offensive odour are created by the anaerobic decay of wet organic matter such as flesh, manure, feed or silage. For example, odour originating from livestock manure are a result of a broad range of over 168 odour-producing compounds. Warm temperatures enhance anaerobic decay and foul odour production, as represented in Figure 1.

Odour sources can be classified as:

• Point Sources: Point sources are confined to emissions from vents, stacks and exhausts.

• Area Sources: Area sources may be unconfined like swine operations, sewage treatment plant, waste water treatment plant, solid waste landfill, composting, household manure spreading, settling lagoons or a cattle feedlot etc.

• Building Sources: Building sources of odour may like from hog confinement chicken and pig sheds.

• Fugitive Sources: In this source of odour, emissions are of fugitive nature like odour emissions from soil bed or bio-filter surface.

Odour can arise from many sources. Most of the sources are man-made. Garbage/improper dumping in vacant land is a common phenomenon. It leads to foul smell due to putrefaction of dumped garbage, which lies uncollected for days together. Unscientific design of landfill, increased sewage production & improper sewage treatment practices produce unpleasant odour.

Large livestock operations, poultry farms, tanneries, slaughterhouses, food and meat processing industries, and bone mills are among major contributors to odour pollution. Agricultural activities like decaying of vegetation, production and application of compost etc. also contribute to odour pollution.

In urban areas, improper handling of public amenities like toilets of cinema hall, bus/railway stations, hospitals, shopping complex etc. generate pungent odour, which affects the users as well as neighborhood residents. Congested markets do not allow the escape of odour from markets products, thus causing problems to shop-owners as well as to customers.

Vehicular sector also has its share in odour pollution. Rapidly growing vehicular population as well as harmful pollutants emitted by them generate very harmful and pungent odour that have marked effects on pedestrians as well as near-by residents.

Table 1 indicates the various odorous chemicals emitted from industrial operations.