Assessment of phase distribution and removal of metals in anaerobic digesters

A determination of the mobility and bioavailability of metals could provide more comprehensive knowledge about the real environmental potential of anaerobic biodigestion and health risks associated with inappropriately treated wastewater. This study aims to determine the distribution of cobalt, copper, iron, manganese, nickel and zinc among the particulate and dissolved fractions in three wastewater types (molasses, vinasse, and acid mine drainage). Affluent and effluent samples from three bioreactors analyzing each wastewater type were collected and separated into dissolved and total fractions; metal partitioning and removal efficiencies from anaerobic treatment were also evaluated. In the influent, substantial proportions of copper and iron (particulate fraction > 70%) are present in the particulate fraction that can be removed more easily than the dissolved fractions of cobalt, nickel, manganese and zinc (dissolved fraction > 53%), requiring subsequent removal techniques, such as ion exchange. For biotechnological applications, this study indicates the substantial potential of the anaerobic treatment for metal removal as an innovative eco-friendly process that minimizes the use of non-renewable resources.