Abstract
In some water treatment plants, floating foam scum, which concentrates micropollutants such as di-2-ethylhexyl phthalate (DEHP), is a serious problem. We assumed the mechanism of foam scum generation to be as follows: DEHP in water adsorbs onto the gas-liquid interface of bubbles and accumulates on the water surface by floating bubbles, and then is concentrated in foam generated by surface-active matter in raw river water. To apply this mechanism, in this study, the removal of DEPH from river water by generating foam using dispersed bubbles was investigated. When river water passed through a foam generator installed in a strong aerator, foam was continuously generated on the water surface and separated as collapsed-foam water. This collapsed-foam water was yellow-brown, and contained high amounts of suspended solids and colloids. However, the amount of collapsed-foam water generated was very small, less than 1% of the total flow volume. In comparison with suspended solids and dissolved organic matters, DEHP was highly concentrated in the collapsed-foam water. The removal efficiencies of DEHP ranged from 7% to 63% using the foam generator. The use of a simple process involving only intensive aeration and foam collection resulted in a high removal efficiency for hydrophobic micropollutants, such as DEHP, which accumulated in the gas-liquid interface from raw tap water.
