Specially structured materials provide outstanding purification. Water permeates them evenly & coarse particle residues as well as even the finest particle residues are trapped mechanically. After a short run-in period purification bacteria lodge in special foam material & ensure the intensive biological decomposition of toxins. Foam Pads are made from phenol-free foam materials provide biological decomposition of harmful pollutants in addition to mechanical water cleaning. They can be washed-out & reused.