Enhancement of Volatile Fatty Acids Removal by a Co-culture of Microalgae and Activated Sludge

The synergistic effects of a co-culture of Chlorella vulgaris (C. vulgaris) and activated sludge in Volatile Fatty Acids (VFAs) treatment were examined by constructing and comparing the performance of the three reactors (only algae, only activated sludge, coculture). As a result, the addition of the activated sludge stimulated the growth of C. vulgaris up to 2.6-fold, even though the initial algae concentration in the co-culture was only 30% of that in the only algae reactor. The treatment efficiency, which was indicated by the degradation of both the VFAs and nutrients, increased due to the symbiotic relationship of the co-culture of C. vulgaris and activated sludge. For the co-culture of algae and activated sludge, the propionate removal rate was enhanced by approximately 29.5-fold and 2.2-fold, respectively, compared to only algae and only sludge; the butyrate removal rate was also enhanced 6-fold and 1.5-fold, respectively. Both the NH4 (+)-N and PO43- -P removal rate of the reactor with the co-culture was approximately 2 times higher than that of the reactor with the only algae and only sludge. Within 88 h, the removal efficiency of the co-culture reactor reached 98.2%, whereas the removal efficiency was 59.3% and 49.8% for only algae and only sludge reactor, respectively.