Characterization and biofiltration of a real odorous emission from wastewater treatment plant sludge

Biofilters have been widely employed for the treatment of malodorous emissions from sludge handling activities in wastewater treatment plants (WWTPs), although their optimized design has been usually hindered by the lack of information about the dynamics of odorant formation. Besides, the odour abatement efficiency of biofilters has been rarely assessed on an individual odorant elimination basis. In this context, the characterization of odours from WWTP sludge in this study revealed the occurrence of a wide range of chemicals, including reduced sulphur compounds and volatile organic compounds (VOCs), with a dynamic concentration profile. The abatement of these odorants was evaluated in a compost-based biofilter at different empty bed residence times (EBRTs). Removal efficiencies (REs) higher than 99% were recorded for limonene, ketones and benzene, while toluene and DMTS REs exceeded 80% at an EBRT of 60 s. A stable biofilter performance was recorded despite the inlet odorant concentration fluctuations. Conversely, DMS and acetic acid were poorly removed due to their likely formation within the biofilter packing material. No correlation between the odorant elimination efficiency and their individual partition coefficients was herein observed.

► Odours from residual sludge are characterized by a complex chemical composition.
► A high and stable biofilter abatement performance was observed for most odorants.
► Dimethyl sulphide and acetic acid were formed within the biofilter packing material.
► Biofilter removal was not correlated to VOC biodegradability or hydrophobicity.