Abstract

This study evaluated a novel biofilm reactor, the liquid-permeable membrane biofilm reactor, that supplies performance-enhancing chemicals directly to the base of a biofilm. The chemicals are supplied via a liquid-permeable membrane that serves as the biofilm support. Two studies were carried out. In the first, a denitrifying biofilm was established on the membrane, and then chlorate was added via the membrane to enhance the abundance of specialized (per)chlorate-reducing denitrifying bacteria. Approximately 98% denitrification was maintained throughout the experiment, but the addition of chlorate resulted in an increase in the relative abundance of putative (per)chlorate reducing bacteria by around 15%. In the second study, a nitrifying biofilm was first established, achieving approximately 70% ammonium removal. Then, a protozoan inhibitor (cycloheximide) was added via the membrane, resulting in an increase in biofilm thickness and an increase in ammonium removal to 93%. Biofilm image analysis identified the mass transport mechanism from membrane to biofilm as a combination of advection and diffusion. These studies demonstrate the viability and effectiveness using a liquid-permeable membrane to supply performance-enhancing chemicals to a biofilm growing on the membrane surface.