This study is focused towards assessing the underlining mechanism behind odor generation in sewage treatment facilities 

(STP) and finding worst possible conditions for maximum odor generation in case of treatment failure. Initially, a total of 

seven wastewater samples and one solid sludge sample was collected and characterized from different treatment units of 

a STP including influent wastewater coming out of a septic tank. Odor generation from these different wastewaters and 

solid sludge sample was examined under various operating condition of temperature, pH and mixing speed. The results 

showed that in general increasing temperature increased odor production, whereas pH behaved differently depending on 

wastewater type with higher odor generation at low pH for sludge thickening sample and at high pH condition for aeration

tank sample. The maximum odor generation (total gas concentration of 20848834 ppb and SOAV of 13904188) was 

for sludge thickening sample at 25 °C, 7 pH and 60 rpm agitation. The odorous gas was mainly composed of reduced 

sulfur compounds, namely hydrogen sulfide, methyl mercaptan, dimethyl disulfide and dimethyl sulfide along with low 

concentrations of phenol and ammonia for all the different samples, however, their relative proportions varied depending

upon wastewater sample and experimental conditions used. Different volatile organic compounds such as aldehydes 

(mainly formaldehyde), ketone and methyl esters were present in liquid samples from different incubations which are also 

of concern from odor generation. The findings provide critical insights into optimizing treatment processes which will help 

in future to implement effective odor control measures.