Enrichment of nitrifying microbial communities from shrimp farms and commercial inocula
Paungfoo, C.; Prasertsan, P.; Intrasungkha, N.; Blackall, L.L.; Bhamidimarri, R.
Water Science and Technology a Journal of the International Association on Water Pollution Research 48(8): 143-150
2003
ISSN/ISBN: 0273-1223 PMID: 14682581 Document Number: 554535
Nitrifying bacteria were selected from shrimp farm water and sediment ("natural" seed) in Thailand and from commercial seed cultures. The microbial consortia from each source giving the best ammonia removal during batch culture pre-enrichments were used as inocula for two sequencing batch reactors (SBRs). Nitrifiers were cultivated in the SBRs with 100 mg NH4-N/litre and artificial waste water containing 25 ppt salinity. The two SBRs were operated at a 7-day hydraulic retention time (HRT) for 77 days after which the HRT was reduced to 3.5 days. The amounts of ammonia removed from the influent by microorganisms sourced from the natural seed were 85 and 92% for the 7-day HRT and the 3.5-day HRT, respectively. The ammonia removals of microbial consortia from the commercial seed were 71 and 83% for these HRTs respectively. The quantity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was determined in the SBRs using the most probable number technique. Both AOB and NOB increased in number over the long-term operation of both SBRs. According to quantitative fluorescence in situ hybridization (FISH) probing, AOB from the natural seed and commercial seed comprised 21+or-2% and 30+or-2%, respectively of all bacteria. NOB could not be detected with currently-reported FISH probes, suggesting that novel NOB were enriched from both sources. Taken collectively, the results from this study provide an indication that the nitrifiers from shrimp farm sources are more effective at ammonia removal than those from commercial seed cultures.