Successful Evaulation of Ten IFAS and MMBR Facilities by applying the Unified Model to Quantify Biofilm Surface Area Requirements for Nitrificaiton, Determine its Accuracy in Prediciting Effluent Characteristics, and understand the Contribution of Media towards Organics Removal and Nitrification

Abstract

The performance of ten full scale wastewater treatment facilities applying IFAS and MBBR systems was evaluated using the Unified Model for Activated Sludge, IFAS and MBBR systems. At each facility, the model was applied to compute the biofilm surface area required to achieve nitrification based on the plant loading, mixed liquor temperature and aerobic mixed liquor MCRT. The effluent ammonium-N was then computed for the amount of biofilm surface area installed and compared to the plant effluent. The analysis showed that the model was able to accurately predict the performance of the facilities (9 out of 9 for which data exists for average loads, 6 out of 6 for peak loads). When the quantity of media installed exceeded the amount computed by the model (% of Media Required that is Installed is > 100%), the observed data showed that the plant was able to achieve less than 2 mg/L under average flow and less than 3 mg/L under diurnal peak load. What is significant is that when the quantity of media installed was less than the amount computed by the model, the plant was not able to nitrify adequately. This was observed at two out of the ten facilities where the model showed that the effluent ammonium-N would exceed 5 mg/L. The results of the model can be applied to determine the additional amount of biofilm surface area (and media) that is required to achieve satisfactory nitrification. Alternatively, for IFAS systems, the model shows how much the aerobic mixed liquor MCRT would have to be increased in lieu of increasing the amount of biofilm surface area. A series of nomographs were generated to enable a designer to determine the biofilm surface area based on temperatures, 4 hour peak to diurnal average loadings and BOD 5 :TKN ratios.

Improved Computational Model (AQUIFAS) for Activated Sludge, Integrated Fixed‐Film Activated Sludge, and Moving‐Bed Biofilm Reactor Systems, Part I: Semi‐Empirical Model Development

“…Earlier versions of the IFAS model were published by Sen and Randall (1996 , 2005 ) and by Sriwiriyarat et al (2005) . Several full‐scale IFAS and MBBR facilities were evaluated using the model, and the results were published in 2006 ( Sen et al, 2006 ). The facilities included Broomfield, Colorado ( Rutt et al, 2006 ); Annapolis, Maryland ( Copithorn et al, 2006 ); Geisselbullach, Germany ( Lessel, 1994 ); Mamaroneck, New York ( Psaltakis et al, 2003 ); and Providence, Rhode Island ( Masterson et al, 2004 ).…”

“…A set of values of coefficients have been developed for use in the model (Table 1). These values are derived by calibrating the model to the data from the continuous‐flow pilot studies ( Sriwiryarat et al, 2005 ) and calibration of the model to several full‐scale MBBRs and IFAS plants ( Sen et al, 2006 ). In and 15, the half‐saturation constants K hydr,EA,PorgN,SS and K hydr,EA,PorgN,SS are 1 mg/L for all electron acceptor (EA) conditions.…”