Exploring key factors in anaerobic syntrophic interactions: Biomass activity, microbial community, and morphology.

The present work evaluated the impacts of microbial communities, biomass activity and sludge morphology on anaerobic syntrophic reactions. Experiments were conducted using mature floc sludge and granular sludge under different food/microbes ratios, and with different sludge types (floc sludge, concentrated floc sludge and granular sludge) and sludge morphology (granules, vortexed granules, and granules with different particle sizes). The results show that the intact granules achieved the most effective syntrophic reaction among all sludge types. The granule structure facilitated the enrichment of syntrophic acetate oxidation bacteria (g_Syner-01 and g_Mesotoga) and methanogens, which corresponds to their superior specific methanogenic activity and high production of communication compounds. Despite the high diffusion and substrate uptake capacities, the disintegrated granules had low H consumption rates, which led to poor syntrophic activities. The results underline the importance of sludge spatial structures in promoting excellent syntrophic activities and the development of diverse microbial communities.