Capacity Enhancement of Enterobacter aerogenes for Heterotrophic Nitrification in Integrated Fixed Film Activated Sludge (IFAS) Wastewater Treatment Process

Enterobacter aerogenes was reported as a bacterium capable of heterotrophic nitrification. It is typically found that autotrophic nitrification is greater in rate than the heterotrophic nitrification. However, heterotrophs are faster growing and lesser sensitive than the autotrophic nitrification bacteria. In this study, the heterotrophic nitrification of E. aerogenes was enhanced with IFAS technology using BioPortz moving media operated at the suspended-growth solids retention time (SRT) of 9 days and temperature of about 28 oC. The experiments were conducted comparatively in the conventional activated sludge (AS) and IFAS systems containing either mixed culture bacteria or E. aerogenes for autotrophic and heterotrophic nitrifications, respectively. The results revealed that E. aerogenes could be enhanced with IFAS technology to complete heterotrophic nitrification with the removal efficiency of 100%. There was no significant difference in nitrification between AS and IFAS systems of two microbes if the systems were properly operated. Ammonia stripping was found in the AS systems whenever nitrification was failed and CO2 was stripped out, resulting in the increase of pH. The clogging of BioPortz media with calcium carbonate precipitates, reducing the IFAS performances, was firstly reported as a result of operating the IFAS systems at the moderate temperature and hardness.