Side-by-Side Comparison of IFAS and CAS Processes at Demonstration Scale at the Lakeview WWTP

Abstract

A full scale demonstration project of an Integrated Fixed Film Activated Sludge process (IFFAS) with floating biofilm carriers has been operating at the Lakeview wastewater treatment plant (Ontario, Canada) since the fall of 2003. In this study, 18 months of data collected on site from July 2005 to December 2006 are analysed and compared to the performance of a conventional activated sludge (CAS) operated in parallel as a control. Both trains had similar loading and suspended solids concentrations, but the IFFAS had 50% more biomass.In the winter, the conventional train operated at the nitrifier washout limit and had unstable partial nitrification. The IFFAS had more stable ammonia removal, and a doubled average nitrification capacity. In the summer when the suspended SRT was less limiting, the difference between the IFFAS and the CAS nitrification performance was marginal. There are indications that the IFFAS train had slightly improved settling characteristics, but it cannot be established if they were due to the anoxic selector installed at the beginning of the train or to the fixed biomass itself. In this demonstration study, the performance benefits of the IFFAS technology were hampered by recurring operational issues including impaired carrier mixing, seasonal foaming in the winter, challenging carrier transfer during tank maintenance, and carrier containment failures.

Effects of Fluctuating Iron Dosage on Nitrification in Integrated Fixed Film and Conventional Activated Sludge Processes

“…The temperature in the biological tanks (Table 5) was around 14 o C in the CAS train, and slightly warmer in the IFFAS train due to higher air flow rates (Stricker et al, 2007). Despite subzero air temperatures and cold runoff from snowmelt and rain events, the wastewater temperature remained mild, in accordance with observations from the previous winter (Stricker et al, 2007).…”

“…This will not impact the direct comparison of the two trains. The average hydraulic, organic and nitrogen loadings were relatively stable as indicated by relative standard deviations (RSD) below 26%, and comparable to the 2006 dataset (Stricker et al, 2007). Marked changes in the primary effluent characteristics are the decrease of soluble PO 4 -P (-83%) and alkalinity (-14%) concentrations, and the presence of substantial amounts of total iron (TFe).…”

“…More details about design and operation can be found in Stricker et al (2007). Copyright ©2008 Water Environment Federation.…”

“…The flow data were used to complete mass flow calculations with the concentrations measured on sampling days. The daily wastage and mixed liquor total suspended solids (MLTSS) data was used to assess the average sludge production of each train, and calculate the daily dynamic SRT (Stricker et al, 2007,Takacs et al, 2008. On sampling days, the sludge production was estimated more accurately using primary effluent fractionation results and equations from activated sludge models (Dold, 2007).…”

“…In Stricker et al (2007), the performance and operation of an integrated fixed film activated sludge (IFFAS) demonstration train was compared with a conventional activated sludge (CAS) train operating in parallel at the Lakeview WWTP (Ontario, Canada) for 18 months in [2005][2006]. Nitrification rates obtained from TKN mass balance calculations showed that the nitrification capacity of the CAS train was severely reduced during the coldest months, while the IFFAS train was able to nitrify the same average load year round.…”