Anaerobic Wastewater Treatment processes are based on the treatment of waste and wastewater by a process called anaerobic digestion. During anaerobic digestion, the organic matter in the waste and wastewaters is transformed to biogas, a mix of methane (CH4) and carbon dioxide (CO2) and a nutrient rich sludge. Biogas can be transformed into heat or power and has therefore a large potential as a renewable energy source. The nutrient-rich sludge can be composted and used as fertilising soil amendment in agriculture. Typical biogas sanitation technologies are biogas settlers, upflow anaerobic sludge blanket (UASB) reactors, anaerobic baffled reactors (ABRs) and anaerobic filters for municipal wastewaters; and biogas reactors (batch, fed-batch PFR or CSTR) for the treatment of slurries and solid organic wastes from agriculture and industry.