Photosynthetically oxygenated acetonitrile biodegradation by an algal-bacterial microcosm: a pilot-scale study

A 43-L column photobioreactor was tested for the treatment of acetonitrile using a symbiotic consortium consisting of a Chlorella sorokiniana strain and a Comamonas strain. Complete biodegradation of 1 g acetonitrile/l was achieved in 79 hours under continuous illumination at 500 μE/m² s and 26 °C. When the photobioreactor was operated at 26 °C under a 14/10 hours light/dark illumination regime at 500 μE/m² s, complete mineralization of 1 g acetonitrile/l was achieved in 111 hours. However, when acetonitrile was supplied at 2 g/l, the biodegradation process was severely inhibited by the increase of pH and NH₄⁺ concentration during cultivation. In addition to saving energy for aeration, the microalgae assimilated 33% of the NH₄⁺ released during acetonitrile biodegradation, which significantly reduces the need for subsequent nitrogen removal.