Volcanic stone (commonly known as pumice or porous basalt) is a functional and environmentally friendly material, which is a very precious porous stone formed by volcanic glass, minerals, and bubbles after a volcanic eruption. Volcanic stone contains dozens of minerals and trace elements such as sodium, magnesium, aluminum, silicon, calcium, titanium, manganese, iron, nickel, cobalt, and molybdenum. It is non radiative and has far-infrared magnetic waves. After a merciless volcanic eruption, after tens of thousands of years, Humans are increasingly discovering its value. It has now expanded its application fields to fields such as architecture, water conservancy, grinding, filter materials, barbecue charcoal, landscaping, soilless cultivation, and ornamental products, playing an irreplaceable role in various industries.

The characteristics of volcanic pumice (basalt) and the physical properties of volcanic rock biological filter materials.
Appearance and shape: No sharp particles, low resistance to water flow, not easy to block, evenly distributed water and air, rough surface, fast film hanging speed, and less prone to microbial film detachment during repeated flushing.

Porosity: Volcanic rocks are naturally cellular and porous, making them the best growth environment for microbial communities.
Mechanical strength: According to the national quality inspection department, it is 5.08Mpa, which has been proven to withstand hydraulic shear effects of different strengths and has a much longer service life than other filter materials.
Density: Moderate density, easy to suspend during backwashing without material leakage, which can save energy and reduce consumption.

Biochemical stability: Volcanic rock biofilter materials are corrosion-resistant, inert, and do not participate in the biochemical reactions of biofilms in the environment.
Surface electricity and hydrophilicity: The surface of volcanic rock biofilter has a positive charge, which is conducive to the fixed growth of microorganisms. It has strong hydrophilicity, a large amount of attached biofilm, and a fast speed.

In terms of impact on biofilm activity: As a biofilm carrier, volcanic rock biofilter media is harmless and has no inhibitory effect on the fixed microorganisms, and practice has proven that it does not affect the activity of microorganisms.
Hydraulics characteristics of volcanic rock biological filter material.

Void rate: The average porosity inside and outside is around 40%, which has low resistance to water. At the same time, compared to similar filter materials, the required amount of filter material is less, and the expected filtering goal can also be achieved.
Specific surface area: With a large specific surface area, high porosity, and inertness, it is conducive to the contact and growth of microorganisms, maintaining a high microbial biomass, and facilitating the mass transfer process of oxygen, nutrients, and waste generated during microbial metabolism.
Filter material shape and water flow pattern: Due to the fact that volcanic rock biological filter materials are non pointed particles and have a larger pore size than ceramic particles, they have less resistance to water flow and save energy consumption when used.

Its characteristics are that it has many pores, light weight, high strength, insulation, sound absorption, fire prevention, acid and alkali resistance, corrosion resistance, and is pollution-free and non radioactive. It is an ideal natural green, environmentally friendly and energy-saving raw material.