Fixed biofilm in polyurethane foam subjected to counter-diffusion for simultaneous nitrification and denitrification

Abstract

Simultaneous nitrification and denitrification (SND) can remove nitrogen from wastewaters in a single based in biofilm unit. The substrate concentration gradients existing in the biofilm, e.g. oxygen, ammonia, nitrite, nitrate and organic matter, allow the coexistence of both nitrifying and denitrifying microorganisms. This study proposed a novel configuration of aerated fixed bed reactor (AFB). The reactor is build using polyurethane foam as material support and is based on counter-diffusion biofilm geometry, which provides less competition by electron donors between aerobic bacteria and heterotrophic denitrifiers enchanting total nitrogen removal in wastewater treatment process with low C/N ratios. Because it is a biofilm developed in a structure of the macropore of the foam, the substrates diffusion may be not runs in a similar way to any other counter-diffusion's biofilm. The polyurethane foam support can protect the biofilm from fluid shearing and collision by providing sheltered anchoring points because of the large pore volumes in the support. In addititon, the biofilm thickness can be managed by adopting different foam thicknesses. Substrate gradients involved in SND will be measured at different biofilm development times and using distinct material support thickness to assess mass flux in the biofilm and how it is impacted by biofilm development over time (pore sealing). (AU)