Phosphorous Removal Kinetics and Operational Issues with a Lab-Scale Advanced IFAS-EBPR-MBR Process
Authors: Majed, Nehreen; Onnis-Hayden, Annalisa; Christensson, Magnus; Welander, Thomas; Gu, April Z.
Source: Proceedings of the Water Environment Federation, WEFTEC 2008: Session 1 through Session 10 , pp. 83-103(21)
Publisher: Water Environment Federation
Abstract:An advanced continuous-flow IFAS-EBPR-MBR system has been established with the aim to achieve simultaneous nitrogen (N) and phosphorus (P) removal and to obtain high quality effluent. With the lab scale IFAS system, effluent phosphorus as low as 0.03 mg-P/L and effluent total nitrogen of 3.14 mg-N/L have been reached. To understand the population distribution in the reactor, both P uptake and release and polyphosphate accumulating organisms (PAOs) population abundance studies were conducted with mixed liquor (ML), with media only or with combination of ML and media. The results indicated that most of the PAO activity was in the ML and the PAO activity in the biofilm was insignificant. Population study showed that about 50% of total cells in ML were PAOs and more than 70% of these PAOs were Accumulibacter type. Fixed film contained less than 2-5% of total PAOs, which contained more than 50% of Accumulibacter type and, nearly all of the PAOs resided in the loosely attached portion of the biofilm on the media. Membrane/nitrate recycle brings both biomass and nitrate from the membrane chamber back to the anoxic zone and change in recycle ratio affected the biomass (MLSS) distribution in different zones of the reactor as observed for recycle ratio of 1Q, 1.5Q and 2.5Q,respectively. Nitrate recycle also impacted the COD, nitrogen species and phosphorus profiles in different reactor zones along the process. Particularly, the P profiles changed from having continuous P release in the anoxic zone at recycle ratio of 1.0 to having anoxic P- uptake in the anoxic zone at recycle ratio of 1.5 and 2.5. Lowest effluent nitrate was found at recycle ratio of 2.5 (3.14 mg-N/L) and effluent P concentrations were 0.03 mg-P/L at ratio of 2.5 and 0.25 mg-P/L at ratio of 1.5. The optimal recycle ratio that yields satisfactory effluent N and P was 2.5 for the system. Incorporation of the membrane system seems to be feasible in the IFAS system which retains the particulate nutrients and solids and provides a high quality effluent.
Document Type: Research Article
Publication date: 2008
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