Biological nitrification-denitrification with alternating oxic and anoxic operations using aerobic granules

Appl Microbiol Biotechnol (2009) 84:11811189 DOI 10.1007/s00253-009-2129-y

ENVIRONMENTAL BIOTECHNOLOGY

Biological nitrificationdenitrification with alternating oxic and anoxic operations using aerobic granules

Sunil S. Adav & Duu-Jong Lee & Juin-Yih Lai

Received: 15 May 2009 /Revised: 4 July 2009 /Accepted: 4 July 2009 /Published online: 21 July 2009 # Springer-Verlag 2009

Abstract Efficient nitrification and denitrification of wastewater containing 1,700 mgl1 of ammonium-nitrogen was achieved using aerobic granular sludge cultivated at medium-to-high organic loading rates. The cultivated granules were tested in a sequencing batch reactor (SBR) fed with 6.4 or 10.2 kg NH4+-N m3day1, a loading significantly higher than that reported in literature. With alternating 2 h oxic and 2 h anoxic operation (OA) modes, removal rate was 45.5 mg NH4+-N g1 volatile suspended solids1h1 at 6.4 kg NH4+-N m3day1 loading and 41.3

2.0 at 10.2 kg NH4+-N m3day1 loading. Following the 60 days SBR test, granules were intact. The fluorescence in situ hybridization and confocal laser scanning microscopy results indicate that the SBR-OA granules have a distribution with nitrifers outside and heterotrophs outside that can effectively expose functional strains to surrounding substrates at high concentrations with minimal mass transfer limit. This microbial alignment combined with the smooth granule surface achieved nitrificationdenitrification of wastewaters containing high-strength ammonium using aerobic granules. Conversely, the SBR continuous aeration mode yielded a distribution with nitrifers outside and heterotrophs inside with an unsatisfactory denitrification rate and floating granules as gas likely accumulated deep in the granules.

Keywords Nitrificationdenitrification . Aerobic granules . Microbial distribution . OLR

Introduction

Nitrogen removal is essential to successful wastewater treatment (Hiscock et al. 1991; Devlin et al. 2000; Kimura et al. 2002; Almasri 2007). Simultaneous nitrification denitrification (SND) processes are typically utilized for nitrogen removal from wastewater (Ruiz et al. 2003). Denitrification is an anoxic process that is sensitive to the level of dissolved oxygen (DO; de Kreuk et al. 2005; Kim et al. 2005; Yang et al. 2003). Notably, SND processes often encounter operational difficulties, such as frequent sludge bulking, low intolerance to shock loading, a large reactor volume needed for suspended sludge systems, and clogging problems for biofilm systems.

Compact biologically efficient aerobic sludge granules with diverse microbial species and excellent settling capabilities have been grown in sequencing batch reactors (SBR) (Morgenroth et al. 1997;...