Evaluation of the performance of iron-supplemented pelletised compost as packing material in biofilters for odour abatement in domestic wastewater treatment plants.

Odour emissions from wastewater treatment plants (WWTPs) are a growing concern due to their negative impact on both workers and surrounding communities, with compounds like H2S, NH3 and volatile organic contaminants (VOCs) contributing to air pollution and potential health issues. Biological technologies, such as biofilters (BFs), are an environmentally sustainable and cost-effective platform for odour control in WWTPs. The use of by-products from WWTPs as packed bed material in BFs would support a circular economy within the water sector. This research evaluates the performance of iron-doped pelletised compost from WWTP sludge by-products as packing material in BFs during the removal of H2S, NH3 and VOCs at empty bed residence time (EBRT). The experimental set-up consisted of three 8-L BFs filled with commercial iron-doped clay pellets (control), pelletised sewage sludge compost and pelletised sewage sludge compost doped with Fe salts. The three BFs achieved a complete removal of H2S and NH3 at EBRTs of 60, 45, 30 and 20 s, while VOC removal exceeded 90 % at EBRTs of 60 and 45 s. The pelletised iron-doped sewage sludge compost supported VOCs removals above 92 % at 60, 45 and 30 s of EBRT. This bed material promoted the growth of genera such as Thermomonas and Thiobacillus among others. This research demonstrated the potential of using WWTP sludge by-products as bed materials in BFs for odour abatement, thus supporting the implementation of the circular economy concept within the integrated water cycle.