High-organic loading treatment for actual molasses wastewater: microbial community shifts corresponding to system development

Molasses wastewater contains high organics, cations and anions, which cause several operational problems for anaerobic biological treatment. To evaluate the high-organic loading treatment system for actual molasses wastewater, we designed a combined system consisting of an acidification tank, thermophilic multi staged (MS)-upflow anaerobic sludge blanket (UASB) reactor, mesophilic UASB reactor and down-flow sludge blanket reactor. At organic loading rate (OLR) of 42 kgCODcr?m-3?d-1 of MS-UAB reactor, the average removal rates of total COD and BOD in combined system were 85?3% and 95?2%, respectively. Besides, by installation of the acidification tank, MS-UASB reactor achieved the low-H2 partial pressure and non-volatile fatty acids accumulation. Along with this, the abundance of several syntrophs such as fatty acids -degrading bacteria increased in MS-UASB and 2nd-UASB reactors. Thus, acidification tank contributed to maintain the favorable environments for syntrophic associations. This study provides new information regarding microbial community compositions in molasses wastewater treatment system.