A study on TOC and nutrients removal in SBR and CFSTR systems in relation to sludge EPS during granulation process

Abstract

The aim of this study was to develop a reactor system which is more efficient for removing TOC and nutrients (nitrogen, phosphorous) from waste water and also to study the role of extracellular polymeric substances (EPS) in their removal rates during aerobic sludge granulation process. Two reactors, including R-1 and R-2 were operated as sequencing batch reactor and continuous flow stirred tank reactor, respectively, for 35 days. Different patterns of food supply and aeration period were maintained in the two reactors. The sludge granule size was around 750 μm in R-1 as compared to R-2 which had average granule size about 340 μm at the end of experiment. EPS contents and TOC removal rates were very high in R-1 than R-2. Nitrogen and phosphorous removal efficiencies were 71 and 56%, respectively, in R-1 and 83 and 64% in R-2. The enhanced nutrients removal rate in R-2 was due to its larger sludge surface area (small granular size) than R-1. Moreover, due to small size particles of R-2, the boundary proteins of EPS were more exposed to nitrogen, therefore electrophilic–nucleophilic interactions between proteins and nitrogen atom of ammonia or nitrate were more profound, and thus increased its removal efficiency, even though R-1 had higher protein contents.

Keywords:

• Extracellular polymeric substances
• TOC
• Nitrogen
• Phosphorous

Notes

Presented at IMSTEC 2013 – 8th International Membrane Science and Technology Conference, Organized by the Membrane Society of Australia, 25–29 November, 2013, Melbourne, Australia