Development of cost-effective and long-lasting integrated technology for H2S control from sludge in wastewater treatment plants

Abstract

Hydrogen sulfide (H₂S) production and emissions from sulfate-reducing bacteria (SRB) during wastewater and sludge (primary sludge and excess activated sludge) treatment and disposal are major concerns due to odor nuisance, corrosion, and health risks associated with H₂S. The widely used chemical dosing approach requires high amounts of chemicals, resulting in high treatment costs. To develop cost-effective and long-lasting technologies for the H₂S control from the sludge, this study proposed integrated methods, including oxidant–glutaraldehyde dosing, aeration–oxidant dosing, and oxidant–iron oxide (Fe₂O₃) dosing. Two oxidants (hydrogen peroxide and sodium chlorite) and one biocide (glutaraldehyde) were selected. All the integrated methods yielded good performances in the H₂S control, from the sludge, due to the synergistic pathways involved, namely, sulfide oxidation by oxidants and Fe₂O₃, and the inhibition of the SRB activity by glutaraldehyde. The optimal removal efficiencies of H₂S in the gas phase and dissolved sulfide in the sludge phase were up to 99.8% and 99%, respectively, within 4 h. Moreover, the integration of oxidants with glutaraldehyde and Fe₂O₃ decreased the hydrogen sulfide release by 66–93%, in prolonged periods of 24–48 h. The integrated oxidant–glutaraldehyde dosing and aeration–oxidant dosing, with treatment costs between 0.5–1.57 USD per m³ sludge, were more cost-effective than the integrated dosing of Fe₂O₃ (12.22–13.68 USD per m³ sludge), as well as the case of dosing a single oxidant (0.53–2.35 USD per m³ sludge). The findings demonstrated that the integrated oxidant–glutaraldehyde and aeration–oxidant dosing could be cost-effective and long-lasting alternatives to the conventional chemical dosings for H₂S control from sludge, oil wells, and reservoirs. This shows the potential industrial application of this work.