Effect of variation in temperature on malodor generation from different units of a wastewater treatment plant

This study investigates the effect of temperature variation on malodor generation across different units of a wastewater treatment plant (WWTP). The results demonstrate that higher temperatures exacerbated odor emission due to increased microbial activity with all the different units showing maximum odorous gas production at the highest temperatures used (35 °C and 45 °C) in this study. The maximum total odor activity value (OAV) of 353106 was obtained for anoxic and anaerobic unit at 45 °C. The variation in composition of odor-causing gases was also dependent on wastewater characteristics than temperature alone. Volatile reduced sulfur compounds, including hydrogen sulfide and methyl mercaptan, were dominant in most wastewater samples, while units with higher dissolved oxygen (DO) content, such as aeration and sedimentation units, exhibited elevated levels of phenol and dimethyl disulfide and reduced H₂S concentration. Analysis of the liquid composition following incubations revealed presence of mainly aldehydes (> 75%) which are produced due to incomplete organic matter degradation, particularly at lower temperatures. Statistical analysis showed positive correlation between temperature and odor generation. DO had negative correlation with H₂S (r =  - 0.78, - 0.93) along with total gas concentration and total OAV, but positively correlated with other gases, namely methyl mercaptan (r = 0.22, 0.97), dimethyl disulfide (r = 0.93, 0.98), phenol (r = 0.99, 0.97), and ammonia (r = 0.99, 0.98). Solids concentration and volatile solids to total solids (VS/TS) ratio had positive correlation with H₂S, total gas concentration, and total OAV (r = 0.68, 0.54, and 0.90). These findings highlight the need for tailored odor management strategies based on temperature fluctuations and unit-specific conditions to optimize WWTP operations and reduce odor emissions effectively.