In order to develop of support medla for bloom reactor, physicochemical properties and attachability of surface of activated carbon, clay mineral, non-clay mineral, and waste mold sand were enamined. Measured physicochemical properties of materials were surface roughness, mean particle size, surface area, hydrophobicity, and surface charge. At a tested materials, activated carbon was the best attachable material and microorganisms were attached $20.1{ imes}10^7CFU/cm^2$ at surface, compared with diatomaceous earth which were attached of <TEX>$9.2{ imes}10^7CFU/cm^2$</times> in our research, surface area and hydrophobicity show- ed more Influence than any other factor on attachment of microorganisms.