Integrated Fixed-film Activated Sludge Research Articles

A biofilm model for engineering design

A biofilm model is presented for process engineering purposes--wastewater treatment plant design, upgrade and optimisation. The model belongs in the 1D dynamic layered biofilm model category, with modifications that allow it to be used with one parameter set for a large range of process situations. The biofilm model is integrated with a general activated sludge/anaerobic digestion model combined with a chemical equilibrium, precipitation and pH module. This allows the model to simulate the complex interactions that occur in the aerobic, anoxic and anaerobic layers of the biofilm. The model has been tested and is shown to match a variety of design guidelines, as well as experimental results from batch testing and full-scale plant operation. Both moving bed bioreactors (MBBR) and integrated fixed film activated sludge (IFAS) systems were simulated using the same model and parameter set. A new steady-state solver generates fast solutions and allows interactive design work with the complex model.

KINETCIS AND NITRIFYING POPULATIONS IN NITROGEN REMOVAL PROCESSES AT A FULL-SCALE INTEGRATED FIXED-FILM ACTIVATED SLUDGE (IFAS) PLANT

KINETCIS AND NITRIFYING POPULATIONS IN NITROGEN REMOVAL PROCESSES AT A FULL-SCALE INTEGRATED FIXED-FILM ACTIVATED SLUDGE (IFAS) PLANTThis study evaluated the nitrification rates and kinetics in an Integrated Fixed-Film Activated Sludge (IFAS) plant with two-stage nitrification process at Broomfield, CO. Batch tests were conducted at site with both fixed-film media and suspended mixed liquor from the two nitrification stages. The nitrification rates for mixed liquor only was 2.64 for stage 1 and 2.0 for stage 2 in unit of...Author(s)Annalisa Onnis-HaydenDaniel DairChandler JohnsonAndreas SchrammApril Z. GuSourceProceedings of the Water Environment FederationSubjectSession 42: Biological Nutrient RemovalDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2007ISSN1938-6478SICI1938-6478(20070101)2007:15L.3099;1-DOI10.2175/193864707787973789Volume / Issue2007 / 15Content sourceWEFTECFirst / last page(s)3099 - 3119Copyright2007Word count473

Oxygen Uptake Rate Tests to Evaluate Integrated Fixed Film Activated Sludge Processes

A modified oxygen uptake rate (OUR) test for characterizing the performance of integrated fixed-film activated sludge (IFAS) processes was developed while monitoring the startup of a full-scale demonstration facility. Data on total biofilm solids, in-basin nitrification rates, and batch nitrification rates were compared to the OUR test. The data was used to investigate dynamic changes in the physical and microbiological parameters during and after plant startup. Nitrification of the carriers was observed to follow different trends than the biofilm total solids during process startup. The process reached high nitrification rates within weeks, whereas the biofilm total solids required more than 50 days to attain a quasi-steady-state. This study illustrated that parameters in addition to biofilm total solids are required to assess activity in nitrifying IFAS processes and oxygen uptake rates can be a useful tool in this regard.

Two Year Case Study of Integrated Fixed Film Activated Sludge (IFAS) at Broomfield, CO WWTP

Two Year Case Study of Integrated Fixed Film Activated Sludge (IFAS) at Broomfield, CO WWTP

Eight Years of Successful Cold Weather Nitrification with Integrated Fixed-Film/Activated Sludge

Eight Years of Successful Cold Weather Nitrification with Integrated Fixed-Film/Activated SludgeIn 1997 the North Buffalo Water Reclamation Facility in the City of Greensboro could not consistently meet their winter permit limit for ammonia-nitrogen. They decided to try a full scale demonstration of Integrated Fixed-Film/Activated Sludge (IFAS) using a new fabric media called BioWeb. IFAS technology adds a high surface area synthetic media directly into the aeration basins of a conventional...Author(s)Sarah B. HubbellRichard PehrsonAndrew SchulerSourceProceedings of the Water Environment FederationSubjectSession 4: Municipal Wastewater Treatment Processes: Hydrodynamic Cavitation Pilot Study for Controlling Cooling Water QualityDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2006ISSN1938-6478SICI1938-6478(20060101)2006:13L.240;1-DOI10.2175/193864706783711108Volume / Issue2006 / 13Content sourceWEFTECFirst / last page(s)240 - 250Copyright2006Word count136

Computer Program Development for the Design of Integrated Fixed Film Activated Sludge Wastewater Treatment Processes

The Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment systems are activated sludge biological nutrient removal processes that have been enhanced by the addition of biofilm support media into the aerobic zone of the system to obtain year round nitrification in activated sludge systems that otherwise could not support it. The objective of this study was to develop a computer package called “IFAS” that allows steady-state simulation of IFAS wastewater treatment processes based on the International Association Water Quality general model for activated sludge and empirical equations for chemical oxygen demand (COD) uptake and nitrification on integrated fixed film developed at Virginia Tech. The current version of the IFAS program supports only sponge-type media; however, the model could be modified for other media if the appropriate equations and required parameters values are known. Data obtained from IFAS sponge media pilot scale plants treating a weak municipal wastewater supplemented by s...

Evaluation of Integrated Fixed Film Activated Sludge Wastewater Treatment Processes at High Mean Cells Residence Time and Low Temperatures

Suspended solids mean cells residence time (MCRT) and temperature are two key parameters for designing Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment processes, as an alternative for achieving year-round nitrification. It has been demonstrated from both full-scale and bench-scale studies that IFAS can accomplish year-round nitrogen removal and denitrification in aerobic zones in winter when operated with suspended growth MCRTs less than the critical MCRT for nitrifiers, thus avoiding increasing reactor or clarifier volumes. The objective of this study was to investigate the performances of IFAS systems that were operated at relative high MCRT compared to nitrifier washout MCRT and low temperature for biological nutrient removal. The comparison between two IFAS systems with Accuweb media in both the anoxic and aerobic zones, and a conventional three zone biological nutrient nemoval (BNR) system was conducted at 10°C with a 10 day MCRT using the UCT/VIP configuration for both systems and feeding with Blacksburg domestic wastewater. Influent flow was split 50% to the first anaerobic reactor and 50% to the first anoxic reactor to enhance denitrification in one of IFAS systems and the conventional BNR control system whereas 100% of the influent flow was fed to the first anaerobic reactor in the other IFAS system. The data from this investigation indicated that the performances of the control and IFAS systems were insignificantly different under the experimental operating conditions for both biological nitrogen and biological phosphorus removal except for IFAS with integrated fixed film media in the anoxic zone and when 50% of the influent was added directly to the first anoxic reactor.

Performance of IFAS wastewater treatment processes for biological phosphorus removal

Integrated fixed film activated sludge (IFAS) is a promising process for the enhancement of nitrification and denitrification in conventional activated sludge systems that need to be upgraded for biological nutrient removal (BNR), particularly when they have space limitations or need modifications that will require large monetary expenses. Several studies have reported successful implementations of IFAS at temperate zone wastewater treatment facilities, typically by placement of fixed film media into aerobic zones. However, nearly all of the implementations have not included enhanced biological phosphorus removal (EBPR) in the upgraded systems. This is possibly because the treatment plants have been operated at low mixed liquor mean cell residence times (MCRTs), and EBPR would wash out of the systems at the low temperatures encountered, making it difficult to maintain EBPR. The primary objective of this study was to investigate the incorporation of EBPR into IFAS systems, and study the interactions between the fixed biomass and the mixed liquor suspended solids with respect to substrate competition and nutrient removal efficiencies. Three pilot-scale UCT/VIP configuration systems were used, one as a control and the other two with Bioweb ® media integrated into some of the anoxic and aerobic reactors. The systems were operated at different MCRTs, and influent COD/TP ratios, and with split influent flows. The experimental results confirmed that EBPR could be incorporated successfully into IFAS systems, but the redistribution of biomass resulting from the integration of fixed film media, and the competition of organic substrate between EBPR and denitrification would affect performances. Also, the integration of fixed film media into the anoxic reactors affected performances differently from media in aerobic reactors.

ACHIEVING ADVANCED WASTEWATER TREATMENT STANDARDS WITH IFAS

Integrated Fixed-film Activated Sludge (IFAS) systems is a hybrid system consisting of both suspended and fixed biomass growth, and it is achieved by incorporating a media that support biofilms in existing aeration basin. By promoting the growth of both carbonaceous-removing and nitrifying bacteria, an integrated fixed-film activated sludge (IFAS) process can improve effluent quality without expanding the plant significantly. The fixed biomass, which grows on the captive support media, provides a higher biomass inventory without significantly increasing the suspended solids inventory. This significantly increases the biological capacity of the system without increasing the physical aeration basin size. The demonstration of the IFAS technology has shown that the installation of fixed film media within an existing aeration basin can provide substantial improvements in effluent quality and process operations. This paper discusses several popular IFAS systems and presents case studies to illustrate the application of the technology.

MODELING AS A TOOL FOR INVESTIGATING IFAS PROCESSES

Utilization of biomass carriers for upgrading existing plants has been receiving increased attention in recent years and has resulted in a growing body of literature. In this study, data sets generated from operational integrated fixed film/activated sludge (IFAS) and fluidized fixed film systems (FFFR) systems reported in the literature were used to assess a model's representation of fundamental outcomes. Three plants were employed for the study: the Waterdown STP (IFAS), the Moorhead WWTF (FFFR) and Royal Roads University Pilot Plant (FFFR). The impact of process variables on performance was evaluated by modifying operational and influent parameters in the model such as SRT, temperature, dissolved oxygen, BOD and TKN (using default model parameters) and comparing the results to reported findings. Similarly, the effect of calibration parameters was evaluated by modifying each parameter considered and recording output nitrification rates. The model accurately predicted the average improvement in nitrification efficiency observed following an upgrade to IFAS in the Waterdown STP at default model parameters. Model predictions of effluent ammonia in a separate stage nitrification FFFR were also within two standard deviations of reported average summer and winter monthly conditions. Trends such as increases in nitrification rate with D.O. and decreases in nitrification rate with reduced temperature and elevated organic loading rate were established by the model. The three calibration parameters tested: Lmax; reduction in diffusion in the biofilm; and liquid film thickness; all had significant consequences for nitrification rates. Influent characterization was found to have the potential to significantly affect nitrification rates in FFFR’s. The predicted results (employing default parameters) corresponded well to available published results, considering the variability in the operational parameters. The model predicted nitrification rates to within 2-9% of the observed means. The model tended to predict lower than observed impacts of D.O. and organic surface loading rate on nitrification rates. Model results for Lmax less than the default value of 0.50 mm tended to further reduce the dependence of nitrification rates on the above noted variables and underestimate nitrification rates. Further research to refine default calibration parameters that can both simulate a reasonable biomass in the system and match observations would therefore prove useful.

Integrated Fixed Film Activated Sludge (IFAS) at the Lakeview WWTP The Real Implementation Issues

Integrated Fixed Film Activated Sludge (IFAS) at the Lakeview WWTP The Real Implementation Issues

Full scale evaluation of nitrification performance in an integrated fixed film activated sludge process

The nitrification performance of an integrated fixed film activated sludge (IFAS) process was compared to a parallel control system at full scale. The IFAS process utilized the Ringlace and Biomatrix looped cord media products. Monitoring and evaluation of the retrofit was divided into two periods. The first monitoring period was from October 3, 1995 to June 20, 1996. The second monitoring period was started on December 2, 1996 and was completed on March 28, 1997. During the first operating period, the maximum media nitrification rate was estimated to be 0.42 kg/d/1000 m of media at an average temperature of 10°C. Settling was also improved. To correct flow short circuiting observed during the first operating period additional aerators were mounted below the media frames and baffles were mounted above existing diffusers. Nitrification performance of the media during the second operating period was found to be marginal. Although the nitrification performance in the control train was not stressed to the same degree as in the 1995/96 period, the likely main cause of the deteriorated performance of the media was a proliferation of bristle worm in the biofilm. The results of this study indicate that proper aeration design, and the prevention and treatment of worm blooms are two important issues in the application of the IFAS process.

Full scale evaluation of nitrification performance in an integrated fixed film activated sludge process

The nitrification performance of an integrated fixed film activated sludge (IFAS) process was compared to a parallel control system at full scale. The IFAS process utilized the Ringlace and Biomatrix looped cord media products. Monitoring and evaluation of the retrofit was divided into two periods. The first monitoring period was from October 3, 1995 to June 20, 1996. The second monitoring period was started on December 2, 1996 and was completed on March 28, 1997. During the first operating period, the maximum media nitrification rate was estimated to be 0.42 kg/d/1000 m of media at an average temperature of 10°C. Settling was also improved. To correct flow short circuiting observed during the first operating period additional aerators were mounted below the media frames and baffles were mounted above existing diffusers. Nitrification performance of the media during the second operating period was found to be marginal. Although the nitrification performance in the control train was not stressed to the same degree as in the 1995/96 period, the likely main cause of the deteriorated performance of the media was a proliferation of bristle worm in the biofilm. The results of this study indicate that proper aeration design, and the prevention and treatment of worm blooms are two important issues in the application of the IFAS process.

Full-scale evaluation of an integrated fixed-film activated sludge (IFAS) process for enhanced nitrogen removal

One of the two trains of the 37,000 m3/d Annapolis, Maryland step aeration activated sludge treatment plant was modified for single-sludge anoxic-aerobic operation, and then fixed-film media were integrated into the aerobic zone to enhance nitrification. Rope-like Ringlace media was selected for integration, and 30,000 meters were installed in a volume of 475 m3 for a pilot demonstration. The purpose of the integrated fixed-film media was to upgrade the short hydraulic retention time (HRT) basin (6 hrs nominal) for efficient, year-round nitrogen removal without construction to increase basin volume. An engineering study had concluded that upgrading the facility for year round complete nitrification, without nitrogen removal, would cost US$24 million. The modified train was operated for 12 months, six in the plug-flow MLE configuration, and six in a step-feed configuration. The integrated Ringlace media increased the nitrification rate per unit volume to 225% of that observed in the control section, attaining a value of 1.75 kg/d NH3-N per linear meter at 15°C. The media also increased denitrification in the aerobic media section to the extent that between 30 and 88% of the nitrates formed in the section were denitrified within it, permitting a potential 25% or more reduction in the volume of the anoxic zone. An IFAS retrofit design was developed which incorporated step-feed operation, and reduced the projected construction cost to US$9.2 million.

Full-scale evaluation of an integrated fixed-film activated sludge (IFAS) process for enhanced nitrogen removal

One of the two trains of the 37,000 m3/d Annapolis, Maryland step aeration activated sludge treatment plant was modified for single-sludge anoxic-aerobic operation, and then fixed-film media were integrated into the aerobic zone to enhance nitrification. Rope-like Ringlace media was selected for integration, and 30,000 meters were installed in a volume of 475 m3 for a pilot demonstration. The purpose of the integrated fixedfilm media was to upgrade the short hydraulic retention time (HRT) basin (6 hrs nominal) for efficient, yearround nitrogen removal without construction to increase basin volume. An engineering study had concluded that upgrading the facility for year round complete nitrification, without nitrogen removal, would cost US$24 million. The modified train was operated for 12 months, six in the plug-flow MLE configuration, and six in a step-feed configuration. The integrated Ringlace media increased the nitrification rate per unit volume to 225% of that observed in the control section, attaining a value of 1.75 kg/d NH33-N per linear meter at 15°C. The media also increased denitrification in the aerobic media section to the extent that between 30 and 88% of the nitrates formed in the section were denitrified within it, permitting a potential 25% or more reduction in the volume of the anoxic zone. An IFAS retrofit design was developed which incorporated step-feed operation, and reduced the projected construction cost to US$9.2 million.

Handbook of Reliability Engineering and Management

High-performance wastewater treatment technologies suited to the urban environment remain largely inaccessible to developing countries due to financial constraints. Instead, inadequate technologies are being used that adversely affect the quality of water resources and limit their sustainability. One high performing technology that offers possible solution is a packaged version of the integrated fixed-film activated sludge (IFAS) system consisting of a 20 m3 aerobic reactor and a 4.2 m3 settlement tank. The present work has investigated aspects of this typically-expensive solution that can be economized to improve its uptake in these countries. To achieve this a life cycle cost analysis (LCCA) was performed and potential savings identified. The results obtained show that the life cycle cost is $0.31/m3 and that costs primarily occurred at the construction stage (11.9%) and the operation and maintenance stage (88.1%) with negligible disposal costs. A reduction of up to 42.4% in construction costs were shown to be accessible by adopting other materials such as high-density polyethylene (HDPE) or to a lesser extent glass-fibre reinforced polymer (GFRP). The greatest single cost in the life cycle was found to be incurred by aeration (48.9%), requiring expenditure of $0.15/m3, however the use of intermittent aeration (IA) could reduce this further to $0.08/m3. Further work is suggested to investigate the broader sustainability of the different aeration strategies in light of these economic results.