The Nitrification and Denitrifying Phosphate Uptake Characteristics of A Combined Biofilm-Activated Sludge Process

• Main Authors: Sheng-Jie You, 游勝傑
• Other Authors: Chaio-Fuei Ouyang
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/08257270005861524521

博士 === 國立中央大學 === 環境工程研究所 === 89 === The TNCU-I process, which added a RBC in the aerobic tank of A2O process, can solve the SRT confliction of nitrifier and phosphate accumulating organisms (PAOs), and the carbon competition of denitrifier and PAOs. In this thesis, the nitrification performance, nitrifier species and abundance were compared with an A2O process by molecular biotechnology. On the other hand, the denitrification/phosphate-uptake or denitrification/phosphate-release characteristics, the existence of DNPAO (Denitrifying Phosphate Accumulating Organisms) of the TNCU-I process was also investigated. Additionally, the optimization of the anaerobic-anoxic-aerobic tank of the TNCU-I process was also performed. The results showed that the nitrification stability, specific nitrification rate and total nitrogen removal efficiency of TNCU-I process were all higher than A2O process. It was also proven that the RBC biofilm in the TNCU-I process could compensate for the overall nitrification performance when the TNCU-I process is operated at a low SRT. Additionally, the genera Nitrosospira and Nitrospira were identified as the predominant ammonia-oxidizer and nitrite-oxidizer among TNCU-I activated sludge, TNCU-I RBC biofilm and A2O activated sludge. It was also showed that the nitrifier abundance of TNCU-I activated sludge was higher than TNCU-I RBC biofilm and A2O activated sludge. The denitrification/phosphate-uptake experiments showed that the DNPAO contributed 47% of overall phosphate uptake and 42% of denitrification performance. Thus, the existence of DNPAO was advantageous for de-nitrogen and de-phosphate. The batch result also showed that the phosphate uptake rate increased with the increase of intracellular PHA of the sludge. Besides, the present of residue COD in the bulk solution enhance the phosphate uptake, but decrease the phosphate release performance. This implied that the DNPAO and non-DNPAO tend to take up more phosphate when it take up more COD, release more phosphate and accumulate more PHA in the anaerobic condition. Additionally, the DNPAO need more than 2 hrs anaerobic hydraulic retention time for competition the carbon with non-DNPAO. According to the reaction kinetics of the batch and pilot plant experiments, the optimum operation conditions of TNCU-I process are: SRT=10 days, HRT=10 hrs, the volume ratio of anaerobic:anoxic:aerobic is 3:5:2, 1-2 RBC were added in the aerobic tank, the recycled nitrification liquid and recycled sludge are 3.5 and 0.5 times of influent flow, and the DO is 2.0 mg/l. In the TNCU-I activated sludge, both nitrifier and DNPAO-like bacteria was identified. The nitrifier species in the RBC biofilm was more diverse, and a certain denitrifier was identified. This revealed that the RBC biofilm could contribute to nitrification and denitrification performance. Additionally, a lot of filamentous bacteria was also identified might be due to the dense biofilm structure. In both samples, the Proteobacteria was the predominant bacteria. The β-subclass, γ-subclass and ε-subclass were the common bacteria that was observed in both samples. The Cytophagales group and Flavobacteria group were also present in activated sludge and RBC biofilm, respectively. No gram positive bacteria was observed in activated sludge but in RBC biofilm.