Under anaerobic conditions organic compounds can serve as the electron donors or electron acceptors during biodegradation processes. Anaerobic reductive bioremediation is the practice of adding biologically available amendments, referred to as organic substrates or electron donors, to groundwater to generate and sustain anoxic conditions. Microbial growth will both consume organic material, oxygen and other electron acceptors. Fermentation reactions thus take place on excess organic material, generating in turn hydrogen that allows anaerobic biological processes that reduce oxidized contaminants such as halogenated compounds to innocuous end products. Halogenated compounds serve as electron acceptors and undergo reductive dehalogenation under anaerobic conditions in the presence of an electron donor (USEPA 2013).