Fate of the fungicide dodemorph during anaerobic digestion of biological waste

The aim of this study was to examine the stability and distribution of the fungicide dodemorph during anaerobic digestion of biological waste, including a short subsequent aerobic treatment. Three reactor experiments were conducted. The influences of pH and dissolved organic carbon (DOC) were further studied in batch experiments. The reactor experiments showed no decrease in the concentration of dodemorph, indicating stability of the fungicide. In connection with the results of the batch experiments, a clear pH-dependency of the partitioning of dodemorph between solid and water phase could be shown. At pH values below the pK(a) value of 7.8, protonated dodemorph molecules predominate. However, a release into the water phase was only observed at pH values of 5 and below. It can be assumed that in the pH range between 5 and 7.8 dodemorph forms bonds with carboxyl groups of organic matter. Dodemorph was not completely extractable from the solid waste matrix due to strong bonds with the organic matter. Solubilising effects by water ingredients of the process water were not apparent.