Performance of Mobile Biological Attached Growth Systems

Abstract

This project aimed at investigating the treatment performance of a pilot-scale mobile attached growth system (moving bed biofilm reactor (MBBR) /suspended aerated filer (SAF)), using a spherical carrier media (Media 1) with a protected surface area of 112 m2.m-3. The pilot scale reactor had a volume of 2 m3 and it was fed continuously with settled wastewater coming from a full-scale municipal wastewater treatment plant (WWTP). Different organic loads were applied to study the efficiency of organic and ammonia removal and to understand what was the maximum organic loading rates that could be applied. The study was carried out for a period of six months. The organic loadings applied were 6, 8 12 and 16 g m-2 d-1. For organic loads of 12 g COD m-2 d-1 the soluble COD removal efficiency ranged from 38 ± 11%, corresponding to surface loading rate 2.35 ± 0.8 g COD m-2 d-1 and removal rate of 0.9 ± 0.6 g COD m-2 d-1. The soluble BOD, removal efficiency ranged from 92 ± 4%, corresponding to surface loading rate of 0.61 ± 0.20 BOD m-2 d-1 and removal rate of 0.57 ± 0.21 g BOD m-2 d-1. The nitrification, efficiency ranged from 65 ± 22%, corresponding to loading rate of 0.86 ± 0.16 g N-NH4+ m-2 d-1 and removal rate of 0.63 ± 0.19 g N-NH4+ m-2 d-1. The second part of the project aimed to determining the external mass transfer and the boundary layer thickness of the biofilm developed in media with different protected surface areas (112 m2.m-3- Media 1, 220 m2.m-3 - Media 2 and 348 m2.m-3 - Media 3). A lab scale MBBR/SAF with a volume of 30L containing the media (with biofilm) and wastewater was subjected to different mixing intensities. The mass transfer coefficient and boundary layer thickness obtained ranged from 2.77 – 4.90 m d-1 and 35.53 – 85.81 μm for Media 1, from 2.24 – 15.61 m d-1 and 11.14 – 77.5 μm for Media 2 and, from 1.80 – 15.90 m d-1 and 11.0 – 96.73 μm for Media 3, respectively.