Removal of selenium from sewage sludge ash was investigated by using chemical leaching and microbial reduction. Leaching of selenium was promoted by ash washing using dipotassium hydrogen phosphate orsodium carbonate solution. As a result, the leaching concentration of selenium from the washed ash was reduced. The selenium concentration in leachate was reduced to less than the effluent standard by using a selenium-reducing bacterium.
Estuary sedimentation often blocks flood passage and navigation.This study was done to clear changes of flow condition by presence of a tidal pond（UTSURO），focused on a tide change. The results are summarized as follows:・ As long as a tidal pond is located near a sea and its area is not so large, the water level in the pond almost corresponds to that in the sea, and the flow discharge into and out of the pond is proportional to the area ofthe pond.・ When the length of a tidal channel is near a multiple of the odd quarter of wave length, resonance occurs in the tidal channel.・ The Naka River estuary in Japan and the Huangpu River estuary in China satisfy the resonance condition, and their depths are kept deep.・Sedimentation at the Yellow River Estuary should be controlled by this method.