Effect of Microstructure on Water Purification Capacity of Microorganism-Supported Porous Alumina

Abstract

The influence of pore structure on the water purification ability of microorganism-supported alumina body was investigated. Porous alumina bodies having various pore sizes and pore volumes were prepared by changing the amount of pore forming agent with different particle size added. Furthermore, the influence of firing temperature on microstructure was investigated. The loading of the microorganisms on the alumina porous body was carried out by immersing the alumina porous body in a culture solution containing yeast, lactic acid bacteria and Bacillus natto for 5 days. The water purification ability of the alumina porous body carrying microorganisms was evaluated by measuring the change in COD after immersion of the porous body for a predetermined time in model waste water having an initial COD value of 180 ppm prepared using glycine and D(+)-glucose. From the results of the SEM observation, adhesion of microorganisms and formation of biofilm were confirmed on the surface and near the pores of the alumina porous body. The decreasing ration of COD of model waste water was largely influenced by the pore volume rather than pore volume of the alumina porous body and increased as the pore volume increased. Moreover, in order to obtain a higher water purification ability, it is preferable that the pore volume of the alumina porous body is above 0.25 cm³/g. When the firing temperature is high, the surface of the alumina porous body became smooth, so microorganisms were less likely to adhere. As a result, the water purification ability of the porous alumina fired at high temperature tends to be lower as compared with that fired at lower temperature.