Pumice

Pumice is a very porous form of volcanic igneous rock formed by the rapid cooling and hardening of lava in volcanic eruptions Due to its low specific gravity, high porosity, and excellent filtration properties pumice is an aggressively filtering alternative to sand and anthracite in a variety of water treatment applications. The pumice media filters, due to their higher total flow volumes can be used for the filtration of waters with a high suspended solids concentration. The low specific gravity and high porosity of pumice make it ideal for these applications and treatment processes.

Advantages:
Pumice has several advantages over other filtration media such as expanded clay, anthracite, & sand. Comparison tests done between deep bed sand and pumice filters for treating water found pumice to be superior in turbidity removal performance and head loss. Pumice is ideal for the capture and retention of cyanobacterial toxins and other impurities found in fouled drinking water.
Benefits of Pumice for Filtration Applications include:

Improved filtration rates
Less energy consumption
Less intensive backwash requirements
Better filtration bed expansion
Larger effective surface area
Low-cost filter refurbishment

Pumice as an Odor Control Media:
Pumice is used in biological scrubbers that remove the nasty stuff from wastewater and industrial emission gases—H2S, mercaptans, and VOCs.

Benefits of Pumice for Odor Control: