Biological iron and manganese removal utilizing indigenous iron and manganese oxidizing bacteria (IRB hereafter) in groundwater can also be applied to arsenic removal according to our pilot-scale test. The arsenic removal probably occurred through sorptio Biological iron and manganese removal utilizes indigenous iron and manganese oxidizing bacteria (IRB hereafter) in groundwater can also be applied to arsenic removal according to pilot-scale test. The arsenic probably probably probably probably occurred