Effects of SRT and DO on nutrient removal in a combined AS-biofilm process

S. H. Chuang, C. F. Ouyang, H. C. Yuang, S. J. You

Research output: Contribution to journalConference articlepeer-review

45 Scopus citations


This study examines the effects of sludge retention time (SRT) and dissolved oxygen (DO) on COD, nitrogen and phosphorus removal in a combined activated sludge - biofilm process. Various SRT (5, 10, 12 and 15 days) and dissolved oxygen (0.1, 0.5, 1.0 and 2.0 mg/l in aerobic stage) conditions are performed during the hybrid process. Experimental results indicate that SRT significantly affects the behavior of nitrogen and phosphorus removal, although the variation of COD removal is only slight in different SRT experiments. The SRT should be controlled for longer than 10 days to achieve efficient nitrogen removal. However, a SRT less than 12 days is deemed necessary to complete the phosphorus removal. The process displays similar characteristics when dissolved oxygen is operated between 1.0 to 2.0 mg/l in the aerobic stage. Moreover, analyzing polyhydroxyalkanoates (PHAs) reveals that phosphorus release and uptake are closely related to PHAs accumulation and utilization, respectively, during anaerobic, anoxic and aerobic stages of the process. The ratio of phosphorus uptake and PHAs utilized, r(P/PHAs), denotes a dissimilar trend during anoxic and aerobic stages. The sludge has a high efficiency in utilizing PHAs for phosphorus uptake in anoxic stage when it is under lower COD-SS loading conditions. The value of r(P/PHAs) ranges from approximately 0.1 to 1.0 mg P/mg PHAs. In addition, experimental results also demonstrate that anoxic phosphorus uptake can improve phosphorus removal in biological nutrient removal processes.

Original languageEnglish
Pages (from-to)19-27
Number of pages9
JournalWater Science and Technology
Issue number12
StatePublished - 1997
EventProceedings of the 1997 6th IAWQ Asia-Pacific Regional Conference, Asian Waterqual'97 - Seoul, South Korea
Duration: 20 May 199723 May 1997


  • Biofilm
  • Denitrification
  • Nitrification
  • Nutrient removal
  • Phosphorus uptake
  • Polyhydroxyalkanoates (PHAs)


Dive into the research topics of 'Effects of SRT and DO on nutrient removal in a combined AS-biofilm process'. Together they form a unique fingerprint.

Cite this