Exploring the relationship between viscous bulking and ammonia-oxidiser abundance in activated sludge: A comparison of conventional and IFAS systems
| Autor: | Michael D. Short, Helen Beard, Ben van den Akker, Uwe Kaeding, Steven Giglio |
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| Přispěvatelé: | Van Den Akker, Ben, Beard, Helen, Kaeding, Uwe, Giglio, Steven, Short, Michael D |
| Rok vydání: | 2009 |
| Předmět: |
Environmental Engineering
Carbon-to-nitrogen ratio Carbohydrates Biomass carbon-to-nitrogen ratio AOB Bioreactors Ammonia Sludge bulking Molasses Food science Nitrosomonas Waste Management and Disposal Water Science and Technology Civil and Structural Engineering sludge bulking biology Sewage Chemistry ammonia-oxidising bacteria Ecological Modeling Environmental engineering Proteins activated sludge plant biology.organism_classification IFAS Pollution Waste treatment qPCR Activated sludge carbohydrate polysaccharide Nitrification EPS protein Bacteria |
| Zdroj: | Water research. 44(9) |
| ISSN: | 1879-2448 |
| Popis: | This study investigated the nature of viscous sludge bulking within a molasses-fed integrated fixed-film activated sludge (IFAS) and conventional activated sludge (AS) plant by routinely measuring the total carbohydrate and protein fractions of the mixed liquor (ML). The impacts of sludge settleability and plant performance on the relative abundance of ammonia-oxidising bacteria (AOB) (Nitrosomonas oligotropha-cluster) were also investigated using quantitative polymerase chain reaction (qPCR). Results showed that sludge volume index (SVI) correlated positively with the amount of ML total carbohydrate in both the IFAS and traditional AS plants, highlighting the influential role that ML polysaccharide concentration plays on sludge settleability in these reactors. Results also revealed a negative relationship between the AOB/total Bacteria ratio and SVI, demonstrating that a poor settling sludge generally coincided with periods of relatively low AOB abundance. The existence of these relationships suggests that readily available organic carbon (molasses) was likely to have been present in excess in these systems. Our qPCR results also showed that concentrations of both AOB and total Bacteria genomic copies detected within the ML of the IFAS and conventional AS plants were remarkably similar. For the IFAS system, results showed that the ML supported an equivalent number of AOB (per gram of biomass) to that detected on the plastic IFAS media carriers, suggesting that the suspended biomass fraction plays an equally important role in the overall nitrification performance of these systems. Interestingly, large observed variations in AOB and AOB/total Bacteria ratio measured within both the ML and IFAS media carriers had no measurable impact on the apparent nitrification performance of these systems; indicating the presence of some excess or 'reserve' nitrifying capacity above that which is required for effective plant performance. Results presented here also constitute the first known side-by-side comparison of the distribution of AOB in IFAS and conventional racetrack-like AS plants at the full-scale level. Refereed/Peer-reviewed |
| Databáze: | OpenAIRE |
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