| Summary: | 博士 === 國立成功大學 === 環境工程學系碩博士班 === 101 === Ammonia-oxidizing bacteria (AOB) are the main contributor in the first step of nitrification in activated sludge systems. Recently, the widely distributed ammonia-oxidizing archaea (AOA) have been reported in natural environments with potential important role in nitrification, but little
information is available about AOA in activated sludge systems. Survey of AOA/AOB community structures in activated sludge systems located at different countries revealed that AOA/AOB population didn’t restricted by geographical location.
A four-year monitoring of a municipal wastewater treatment plant showed that salinity may play an important role on AOA and AOB. Based on the real-time quantitative polymerase chain reaction (qPCR) of ammonia monooxygenase subunit A (amoA) genes, an increase in the AOB amoA gene copies occurred with a decrease in the wastewater salinity level. A
corresponding decrease in the average AOA/AOB ratio was observed. Phylogenetic analyses on amoA gene sequences indicated that Nitrosomonas marina-like AOB and “Thaumarcheota I.1a” (marina group) AOA were dominant when the wastewater salinity level fluctuated at high values with an average of 4.83 practical salinity unit (psu), while Nitrosomonas urea-like AOB and “Thaumarcheota I.1b” (soil group) AOA became dominant when the wastewater salinity decreased to a more stable lower level. Based on the
amoA-based terminal restriction fragment length polymorphism (T-RFLP)analyses, results from this study demonstrated that the observed shift in AOB and AOA populations is likely caused by a change of the wastewater salinity level. Moreover, time lag effect was proposed in this study for evaluating the relationship between environment factors and slow-growing microorganism (like AOA and AOB) population.
To clarify the impact of the salinity on AOA and AOB, bioreactors seeded with the same inoculums were operated under the same conditions but with different salinity level (0.25% and 3.5%) for more that 300 days. Both bioreactors were able to achieve over 95% of nitrification efficiency.
Distinct AOA and AOB populations were enriched after 123 days and 273 days operation based on results of T-RFLP and cloning and sequencing targeting on amoA gene. Real-time qPCR results targeting on amoA gene showed that AOA predominated in both reactors in most of the operation
period (AOA/AOB ratio over 1). Higher AOA/AOB ratio values were observed in high salinity reactor. Comparing these two reactors, it shows that salinity provide AOA advantage to outnumber over AOB. Batch test results showed that activated sludge enriched from different salinity performed different kinetics characteristics.
Our results clearly presented salinity affected ammonia-oxidizing archaea and bacteria on their abundance, community structure, and kinetics characteristics. Moreover, principal coordinates analysis result showed that AOA and AOB community change level, which resulted from the environment change, were different.
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