Arsenic Oxidation State in the Presence of Microorganisms: Examination by Differential Pulse Polarography

Abstract
Differential pulse polarography was used to monitor changes in the oxidation state of arsenic when arsenic oxyacids were acted upon by microorganisms. Arsenite is chemically altered in raw sewage, activated sludge, and sewage effluent under aerobic conditions; it was shown that in the presence of oxygen, activated sludge oxidizes arsenite to arsenate. Activated sludge under anaerobic conditions first reduces arsenate to arsenite. At longer times the arsenite apparently is further reduced. Aerobic cultures of Pseudomonas fluorescens also reduce arsenate to arsenite.