Heavy metal contamination of anaerobically digested waste activated sludge hampers its reuse as fertilizer or soil conditioner. Conventional methods to leach metals require aeration or the addition of leaching agents. This paper investigates whether metals can be leached from waste activated sludge during the first, acidifying stage of two-stage anaerobic digestion without the supply of leaching agents. These leaching experiments were done with waste activated sludge from the Hoek van Holland municipal wastewater treatment plant (The Netherlands), which contained 342μgg-1 of copper, 487μgg-1 of lead, 793μgg-1 of zinc, 27μgg-1 of nickel and 2.3μgg-1 of cadmium. During the anaerobic acidification of 3gdry weightL-1 waste activated sludge, 80-85% of the copper, 66-69% of the lead, 87% of the zinc, 94-99% of the nickel and 73-83% of the cadmium were leached. The first stage of two-stage anaerobic digestion can thus be optimized as an anaerobic bioleaching process and produce a treated sludge (i.e., digestate) that meets the land-use standards in The Netherlands for copper, zinc, nickel and cadmium, but not for lead.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUK-C1-017-12
Acknowledgements: This work was part of the SOWACOR project; award no. KUK-C1-017-12 of the King Abdullah University of Science and Technology (KAUST). This work was co-funded by NUFFIC (Netherlands Organization for International Cooperation in Higher Education) through the NFP (Netherlands Fellowship Programme) and by the DUPC (DGIS UNESCO-IHE Programmatic Cooperation).
ASJC Scopus subject areas
- Environmental Chemistry
- Environmental Engineering
- Waste Management and Disposal