Evaluation of support materials for the immobilization of sulfate-reducing bacteria and methanogenic archaea

This paper reports on the adhesion of sulfate-reducing bacteria (SRB) and methanogenic archaea on polyurethane foam (PU), vegetal carbon (VC), low-density polyethylene (PE) and alumina-based ceramics (CE). Anaerobic differential reactors fed with a sulfate-rich synthetic wastewater were used to evaluate the formation of a biofilm. The PU presented the highest specific biomass concentration throughout the experiment, achieving 872 mg TVS/g support, while 84 mg TVS/g support was the maximum value obtained for the other materials. FISH results showed that bacterial cells rather than archaeal cells were predominant on the biofilms. These cells, detected with EUB338 probe, accounted for 76.2% (±1.6%), 79.7% (±1.3%), 84.4% (±1.4%) and 60.2% (±1.0%) in PU, VC, PE and CE, respectively, of the 4′6-diamidino-2-phenylindole (DAPI)-stained cells. From these percentages, 44.8% (±2.1%), 55.4% (±1.2%), 32.7% (±1.4%) and 18.1% (±1.1%), respectively, represented the SRB group. Archaeal cells, detected with ARC915 probe, accounted for 33.1% (±1.6%), 25.4% (±1.3%), 22.6% (±1.1%) and 41.9% (±1.0%) in PU, VC, PE and CE, respectively, of the DAPI-stained cells. Sulfate reduction efficiencies of 39% and 45% and mean chemical oxygen demand (COD) removal efficiencies of 86% and 90% were achieved for PU and VC, respectively. The other two supports, PE and CE, provided mean COD removal efficiencies of 84% and 86%, respectively. However, no sulfate reduction was observed with these supports.