| The release of metals from bottom sediments sometimes significantly affects water quality through eutrophication in dam reservoirs. Various studies have been conducted on countermeasures for controlling release of metals from sediments by supplying oxygen to water using air: by the Microbubbles system or injecting surface water into bottom layers of dam reservoirs. We investigated a novel water quality restoration technology: using pure oxygen gas to supply water with supersaturated dissolved oxygen to the bottom layer, controlling the release of metals from sediments.We conducted a field investigation in a dam reservoir using this technology from summer to autumn, 2008. Water temperature, DO concentration and ORP in a water column were monitored regularly by a multi-parameter water quality meter during the experiment. We also observed nutriments, metals and DOC concentrations in the water column. The DO supply system was continuously operated, but the latitude of the oxygen supply apparatus was changed to maintain the DO concentration through the bottom layer. As a result, a significant increase in DO concentration in a broad spectrum of the bottom layer was observed without destruction of the stratification, resulting in the decrease of iron and arsenic concentrations in the bottom layer of the water column. |
