Sequential treatment of PTA wastewater in a two-stage UASB process: Focusing on p-toluate degradation and microbial distribution

► Two-stage UASB process was investigated focusing on p-toluate (pTOL) degradation. ► With the given process scheme, the pTOL removal capacity remarkably increased. ► The methane yield on pTOL was 0.12 L/g-COD at a true steady state. ► Acidogens enriched in both stages could degrade all aromatic pollutants. ► Different acidogen and methanogen distribution was clearly observed in each stage.