Community changes during start-up in methanogenic bioreactors exposed to increasing levels of ammonia.
To investigate the methanogenic population dynamics during the start-up under gradually increasing free ammonia levels, five mesophilic UASB reactors seeded with different sludges were operated for 140 days. Changes in the methanogenic community investigated by using 16S rDNA/rRNA based molecular methods such as denaturing gradient gel electrophoresis (DGGE), fluorescent in-situ hybridization (FISH), cloning and DNA sequencing. Free ammonia nitrogen (FAN) in the reactors was gradually increased from 50 to 130 mg l(-1) by increasing total ammonia nitrogen (TAN) from 1000 to 2500 mg l(-1) in the feed and keeping reactor pH at 7.7 in the active zone. Even at highest FAN level, COD and VFA removal efficiencies above 90 and 98% were obtained, respectively. However, Methanosaeta-related species mainly prevailing in seed sludges were substituted for Methanosarcina as the abundant methanogens although reactor performances were almost comparable and constant.
Calli
B
B
Department of Environmental Engineering, Marmara University, 34722 Goztepe, Istanbul, Turkey.
Mertoglu
B
B
Inanc
B
B
Yenigun
O
O
D000641:Ammonia / Q000378:metabolism*; D019149:Bioreactors; D004269:DNA, Bacterial / Q000032:analysis; D008697:Methane / Q000032:analysis*; D019640:Methanosarcinales / Q000235:genetics / Q000254:growth & development*; D011157:Population Dynamics; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D014865:Waste Disposal, Fluid / Q000379:methods*
D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D000641:Ammonia; D008697:Methane