**5.6 Anaerobic baffled reactor (ABR)**

Anaerobic baffled reactor (ABR) is a modification of Upper-flow Anaerobic Sludge-Bed Reactor. Anaerobic baffled reactor (ABR) initially gets the organic fraction of municipal solid waste (OFMSW) accompanied by decomposition process of the materials and eventually generates biogas by microorganisms' activities. This kind of reactor can possibly treat wastes with high solid content, and thus, it may be a viable alternative in some situations observed in developing countries. The raising contact time with the sludge (active biomass) results in treatment improvement. ABRs are powerful and able to treat a broad range of wastewater, but both remaining effluents and sludge still require additional treatment in order to be discharged or reused correctly [121, 143].
