Applications of Up-flow Anaerobic Sludge Blanket (UASB) and characteristics of its microbial community: a review of bibliometric trend and recent findings

Interest of research on up-flow anaerobic sludge blanket (UASB) reactors is growing. The meta-analysis of bibliometric data highlighted the growing interest in four diverse topics: (i) energy recovery production; (ii) combination with other treatments; (iii) the study of processes for the removal of specific pollutants and, (iv) characterization of microbial community and granular sludge composition. In particular, the papers pub-lished in the first 6 months of 2021 on this process have been selected and critically re-viewed to highlight and discuss the results, the gaps in the literature and possible ideas for future research. Although the state of research on UASB is to be considered advanced, there are still several points that will be developed in future research such as the consoli-dation of the results obtained on a semi-industrial or real scale, the use of real matrices in-stead of synthetic ones and a more in-depth study of the effect of substances such as anti-biotics on the microbiota and microbiome of UASB granular biomass. To date, few, and conflicting data about environmental footprint of UASB are available and therefore other studies on this topic are strongly suggested.