Researchers conducted experiments to study how bacteria in a sand filter can remove manganese from Dongting Lake groundwater. They found that the amount of bacteria in the filter layer affected the manganese removal ability. The filter needed 60 days to mature and had good manganese removal at a filter velocity of 12 m/h. A pH value of 5 led to rapid increase in effluent manganese content, while an oxidation-reduction potential (ORP) of 720 mV resulted in effective manganese removal. The presence of ferrous ions also influenced the filter's ability to remove manganese.