The volcanic rock,lava stone is corrosion resisted, it is inertia, so it never reacts with biological films. 2、Surface’s electric property and hydrophilcity: Volcanic filter’s surface brings positive charge, so it is favorable for the growt
h of the microorganisms. Its hydrophilcity is very strong, so the attached biological film quantity is large and very fast. 3、The effectives to the biological film activity: as a biological film carrier, the volcanic biological filter is harmless , no suppressive to the fixed microorganisms, the fact proves that it never affects the microorganism’s activity.
poriness：the inside and outside average poriness is about 40%, the resistance to water is very small, comparing with the same kind filter, it costs less, but can reach the expected filtering purpose. 2、The specific surface area: the specific surface area is large, the opening holes are many and inertia, so it is suitable for microorganism to touch and form film, keeping
