Key Laboratory of Northwest Water Resource Environment and Ecology

Fengcheng, China

Key Laboratory of Northwest Water Resource Environment and Ecology

Fengcheng, China
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Yao Q.,China University of Technology | Yao Q.,Key Laboratory of Northwest Water Resource Environment and Ecology | Peng D.-C.,China University of Technology | Peng D.-C.,Key Laboratory of Northwest Water Resource Environment and Ecology
AMB Express | Year: 2017

Nitrification activities and microbial populations of ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were investigated in 10 full-scale biological nutrient removal wastewater treatment plants in Xi’an, China. Aerobic batch tests were used to determine the nitrifying activities while fluorescence in situ hybridization was used to quantify the fractions of AOB and NOB in the activated sludge. The results showed that nitrifying bacteria accounted for 1–10% of the total population. Nitrosomonas and Nitrospira were the dominant bacteria for AOB and NOB respectively. Moreover, the average percentage of AOB was 1.27% and that of NOB was 4.02%. The numerical ratios of NOB/AOB varied between 1.72 and 5.87. The average ammonium uptake rate and nitrite uptake rate were 3.25 ± 0.52 mg (NH4 +–N)/g(VSS) h and 4.49 ± 0.49 mg (NO2 −–N)/g(VSS) h, respectively. Correspondingly, the activity of NOB was 1.08–2.00 times higher than that of AOB. Thus, NOB was the dominating bacteria in nitrifying communities. The year-round data of Dianzicun (W6) also expressed a similar trend. Since NOB had higher activities than that of AOB, a large nitrite oxidation pool could be formed, which guaranteed that no nitrite would be accumulated. Therefore, stable nitrification could be achieved. A conceptual model was proposed to describe the population variation of AOB and NOB in a nitrifying community. © 2017, The Author(s).


Yao Q.,Xi'an University of Architecture and Technology | Yao Q.,Key Laboratory of Northwest Water Resource Environment and Ecology | Peng D.,Xi'an University of Architecture and Technology | Peng D.,Key Laboratory of Northwest Water Resource Environment and Ecology | And 9 more authors.
Journal of Bioscience and Bioengineering | Year: 2016

Successful partial nitrification not only guarantees the inhibition of nitrite oxidation, but also does not excessively retard the ammonia oxidation rate. Therefore, the performance of ammonium oxidizing bacteria (AOB) during partial nitrification is fundamental to this process. In this study, two lab-scale partial nitrification bioreactors containing different inhibition conditions-one with free ammonium (FA) inhibition, the other with free nitrous acid (FNA) inhibition-were used to compare the differences between activity, quantity, aggregation morphology and extracellular polymeric substance (EPS) distribution of AOB. The results showed that although stable, long-term, partial nitrification was achieved in both reactors, there were differences in AOB activity, microbial spatial distribution and EPS characteristic. In the FA bioreactor, FA concentration was conducted at more than 40 mg/L, which had a strong impact on the metabolism of AOB. The activity and quantity decreased by 50%. Higher EPS (42.44 ± 2.31 mg g-1 mixed liquor volatile suspended solids [MLVSS]) and protein were introduced into the EPS matrix. However, in the FNA bioreactor, the FNA concentration was about 0.23 mg/L. It did not reach a level to affect AOB metabolism. The AOB activity and quantity were maintained at high levels and the total EPS content was 28.29 ± 2.04 mg g-1 MLVSS. Additionally, the microscopic results showed that in the FA bioreactor, AOB cells aggregated in microcolonies, while they appeared to be self-flocculating with no specific conformation in the other reactor. β-polysaccharides located inside sludge flocs in the FA bioreactor but only accumulated around the outer layer of activated sludge flocs in the FNA condition. © 2017 The Society for Biotechnology, Japan.


Wang B.-B.,Xi'an University of Architecture and Technology | Wang B.-B.,Key Laboratory of Northwest Water Resource Environment and Ecology | Chang Q.,Xi'an University of Architecture and Technology | Chang Q.,Key Laboratory of Northwest Water Resource Environment and Ecology | And 8 more authors.
Water Research | Year: 2014

Extracellular polymeric substances (EPS) play a crucial role in the formation of activated sludge flocs. However, until now, the EPS are rather classified by the method used for extraction than by a theoretical consideration of their function and composition. In this paper, a new classification paradigm of EPS was proposed, which offered a novel approach to identify the role of EPS in the formation of activated sludge flocs. The current study gave an exploration to distinguish the EPS in the floc level (extra-microcolony polymers, EMPS) and in the microcolony level (extra-cellular polymers, ECPS). It was found that cation exchange resin treatment is efficient to disintegrate the flocs for EMPS extraction, however, inefficient to disaggregate the microcolonies for ECPS harvesting. A two-steps extraction strategy (cation exchange resin treatment followed by ultrasonication-high speed centrifugation treatment) was suggested to separate these two types of EPS in activated sludge flocs and the physicochemical characteristics of EMPS and ECPS were compared. The protein/polysaccharide ratio of ECPS was higher than that of EMPS and the molecular weight of proteins in EMPS and ECPS were found to be different. The ECPS contained higher molecular weight proteins and more hydrophobic substances than the EMPS contained. The result of excitation-emission matrix fluorescence spectroscopy analysis also showed that the EMPS and the ECPS have different fluorescent expressions and the components of EMPS were more diverse than that of ECPS. All results reported herein demonstrated that two different types of exopolymers exist in the activated sludge flocs and the inter-particle forces for aggregation of activated sludge flocs are not identical between the floc level and the microcolony level. It suggested that cation bridging interactions are more crucial in floc level flocculation, while the entanglement and hydrophobic interactions are more important in microcolony level cohesion. © 2014 Elsevier Ltd.

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