Reduction of chlorate with various energy substrates and inocula under anaerobic conditions

Microbial chlorate reduction coupled to the degradation of organic and inorganic compounds was observed with mixed cultures. Chlorate-reducing microorganisms were able to degrade carboxylic acids, alcohols and amino acids. Inorganic compounds oxidized by chlorate-reducing microorganisms were H2S and H2. Concomitant with the disappearance of chlorate, stoichiometric appearance of chloride was detected. Microorganisms carrying out chlorate reduction inhabit a variety of environments including rivers, sediments, soils and waste water treatment plants. However, significant biodegradation of chlorate by these microorganisms did not take place under aerobic conditions. The reduction of chlorate was not affected by the presence of Mn(IV), Fe(III) and sulphate. The environmental fate of chlorate therefore depends on several factors, including the availability of suitable substrates and the absence of molecular oxygen and nitrate. As a consequence, microbial reduction of chlorate will mainly occur in soils and sediments.