Impact of pH conditions and the characteristics of two electrodialysis membranes on biofilm development under semi-realistic conditions

Abstract

The reuse of treated wastewater for irrigation is of increasing importance. The Ecosave farming project developed a new photocatalytic electrodialysis process for desalination and hygienization. However, membrane scaling significantly reduces filtration efficiency. This study investigated biofilm development on anion and cation exchange membranes at a wide pH range in pre-treated wastewater. Epifluorescence microscopic quantification of the biofilm by cell counts and surface coverage together with 16S rDNA gene copy numbers showed stronger biofilm development on the anion exchange membrane (AEM) compared with the cation exchange membrane (CEM) with up to 105 cells mm−2 and 20% surface coverage after three weeks. As the AEM biofilm developed best in neutral and a slightly alkaline pH, the CEM was colonized preferably at alkaline conditions. Extreme pH conditions strongly inhibited biofilm growth, which might help to minimize the maintenance effort by creating those conditions during the operation of the dialysis cell itself.