Integrated Fixed-film Activated Sludge Process Research Articles

Comparing methanol and glycerol as carbon sources for mainstream partial denitrification/anammox in an IFAS process.

This study explored the implementation of mainstream partial denitrification with anammox (PdNA) in the second anoxic zone of a wastewater treatment process in an integrated fixed film activated sludge (IFAS) configuration. A pilot study was conducted to compare the use of methanol and glycerol as external carbon sources for an IFAS PdNA startup, with a goal to optimize nitrogen removal while minimizing carbon usage. The study also investigated the establishment of anammox bacteria on virgin carriers in IFAS reactors without the use of seeding, and it is the first IFAS PdNA startup to use methanol as an external carbon source. The establishment of anammox bacteria was confirmed in both reactors 102 days after startup. Although the glycerol-fed reactor achieved a higher steady-state maximum ammonia removal rate because of anammox bacteria (1.6 ±0.3g/m2/day) in comparison with the methanol-fed reactor (1.2±0.2g/m2/day), both the glycerol- and methanol-fed reactors achieved similar average in situ ammonia removal rates of 0.39 ±0.2g/m2/day and 0.40 ±0.2g/m2/day, respectively. Additionally, when the upstream ammonia versus NOx (AvN) control system maintained an ideal ratio of 0.40-0.50 g/g, the methanol-fed reactor attained a lower average effluent TIN concentration (3.50 ±1.2mg/L) than the glycerol-fed reactor (4.43 ±1.6mg/L), which was prone to elevated nitrite concentrations in the effluent. Overall, this research highlights the potential for PdNA in IFAS configurations as an efficient and cost-saving method for wastewater treatment, with methanol as a viable carbon source for the establishment of anammox bacteria. PRACTITIONER POINTS: Methanol is an effective external carbon source for an anammox startup that avoids the need for costly alternative carbon sources. The methanol-fed reactor demonstrated higher TIN removal compared with the glycerol-fed reactor because of less overproduction of nitrite. Anammox bacteria was established in an IFAS reactor without seeding and used internally stored carbon to reduce external carbon addition. Controlling the influent ammonia versus NOx (AvN) ratio between 0.40 and 0.50 g/g allowed for low and stable TIN effluent conditions.

Upgrading the MBBR Process to Reduce Excess Sludge Production in Activated Sludge System Treating Sewage

Excess sludge production is one of the limitations of the biological activated sludge process. Therefore, the study’s objective is to upgrade the MBBR process to an integrated fixed film-activated sludge (IFAS) process to reduce excess sludge production. Two scenarios were followed in this study to eliminate sludge production in the biological activated sludge process: first, modifying the moving bed biofilm reactor (MBBR) system by increasing the solid retention time (SRT) from 5 to 15 days; and second, upgrading the MBBR process to the integrated fixed-film activated sludge (IFAS) process by applying return activated sludge (RAS) of 50, 100 and 150% with operating hydraulic retention time (HRT) of 6, 12, 14 and 20 h. The results revealed that the first scenario reduced sludge production from 750 to 150 g/day, whereas the second scenario eliminated sludge generation. In the second scenario, operating the system as an IFAS process with complete SRT has eliminated sludge due to sludge decay and cell lysis. In part 3 of the second scenario, the results also showed that the system achieved low effluent pollutants concentrations of 3, 12, 8 and 45 mg/L for BOD, COD, TSS and NO3, respectively. Operating at complete SRT may eliminate sludge production but also result in higher NO3 effluent concentration due to the production of NH3 from sludge decay and cell lysis. To conclude, sludge elimination in an activated sludge system is possible by carefully controlling the process and applying RAS without additional treatment.

Fate of Emerging Contaminants in an Integrated Fixed-Film Activated Sludge Plant

Conventional sewage treatment techniques have shown low removal efficiency for emerging contaminants (ECs). Hence, more efficient treatment systems need to be investigated. The current study suggests that an Integrated Fixed-Film Activated Sludge Process (IFAS) could be one such alternative. The degradation of eight ECs in municipal sewage has been studied during the transition of a pilot IFAS plant to a steady state and compared with the removal of the eight ECs in a conventional sequencing batch reactor (SBR)–based sewage treatment plant at a steady state. In the six weeks before attaining a steady state, the outlet total biochemical oxygen demand, total chemical oxygen demand, and total suspended solids (TSS) decreased from 42 to 10 mg/L, 96 to 26 mg/L, and 38 to 10 mg/L, respectively. The suspended biomass concentration, hydraulic retention, and return sludge rate of the plant were 1,600 mg/L, 6.9 h, and 175% of inflow, respectively. During the transition to a steady state in the IFAS plant, the removal efficiency of Caffeine, Gemfibrozil, and Testosterone was found to increase by 41% (15%–56%), 26% (63%–89%), and 65% (19%–84%) respectively, due to enhanced biological degradation. The SBR was found to be more efficient in the removal of ECs, which could be due to the higher concentration of suspended biomass.

Pilot-scale study based on integrated fixed-film activated sludge process for cement industrial wastewater treatment

Due to the lack of freshwater resources in Egypt, cement wastewater treatment was performed to widen the range of the water used in irrigation to face the massive future water scarcity. In this study, integrated fixed-film activated sludge (IFAS) was used as a biological treatment method. A laboratory pilot was established as a simulation of the IFAS process. The scale-pilot consists of a primary sedimentation tank, an IFAS tank equipped with an air blower, and a final settling tank. Three experimental attempts were performed using 3 different bio-carriers. In the first trial, Luffa sponges were used as natural bio-carriers and polyurethane sponges (PU) as artificial bio-carriers in the second trial, in addition to a combination between Luffa and PU sponges as a hybrid bio-carrier in the third trial. After analyzing the physicochemical properties of wastewater at the national research center in Cairo, the removal efficiency of TSS (total suspended solids), COD (chemical oxygen demand) , BOD(biological oxygen demand), TN (total nitrogen), and TP (total phosphorous) was 94.5%, 87.8%, 90.8%, 75.9%, and 69.4%, respectively in case of using the combination between Luffa and PU sponges. It can be concluded that using IFAS process was effective for cement wastewater treatment and the effluent wastewater met the Egyptian code limitations for reuse in agriculture purposes.

CO-TREATMENT OF LEACHATE AND DOMESTIC SEWAGE AND ITS INFLUENCE ON NITROGEN REMOVAL

Abstract This research investigated the performance of two pilot-scale treatment plants: an activated sludge and a hybrid model type IFAS (Integrated Fixed-Film Activated Sludge), combining sanitary landfill leachate with domestic sewage treatment with the objective of removing organic substances. In order to assess the possible impacts on the treatment, three experimental phases were developed with leachate inputs in the influent composition: 5%, 10% and 20% of the total load of BOD. As can be seen from the results, even with the highest levels of leachate input, there were no significant changes in the behavior of the biological processes. Regarding the oxidation of nitrogen compounds, expressed in terms of TKN, approximately 90% removals were observed for the IFAS process in all the phases. In the Activated Sludge process, removal rates during the study were approximately 70%, indicating poor performance. The kinetic coefficients for the autotrophic metabolism related to the Activated Sludge process remained stable, while a progressive decrease was observed for each stage in the IFAS process. In general, the IFAS process presented better performance than the Activated Sludge process in terms of removal efficiency of nitrogen matter, as well as higher operating stability.

Pilot scale study of sequencing batch reactor (SBR) retrofit with integrated fixed film activated sludge (IFAS): nitrogen removal and design consideration

IFAS process was coupled with SBR operation in a pilot-scale reactor to verify the feasibility and to evaluate the performance of IFAS-SBR. Significant nitrification improvement in the IFAS-SBR system was observed, which is attributed to both the introduction of attached-growth biomass on media carriers and the “seeding effect” by biofilm sloughing.

Operation of an Integrated Fixed-Film Activated Sludge Process to Provide Nutrient Removal and Plant-Wide Energy Savings

Operation of an Integrated Fixed-Film Activated Sludge Process to Provide Nutrient Removal and Plant-Wide Energy Savings

Understanding biofilm diffusion profiles and microbial activities to optimize integrated fixed-film activated sludge process

The integrated fixed-film activated sludge (IFAS) process is widely used in wastewater treatment plants (WWTPs) of China to ensure complete nitrification. However, high aeration intensity in this process requires optimization to reduce its energy footprint. Moreover, understanding microbial activity is also critical for process operation, especially for the biofilm on the carriers which play an important role for nitrogen removal. Here, we integrated process modeling, biomass activity and microbial community analysis in a full-scale IFAS plant, in order to investigate and optimize the process operation for better performance especially in cold climate. The field surveys indicated complete nitrification in the IFAS process, with biofilm contributed two thirds of it. Parameter sensitivity analysis also emphasized the importance of biofilm diffusion profile for process operation, and ammonia limited diffusion profile implied the bulk dissolved oxygen (DO) can be reduced from 8mg/L to 4mg/L. Furthermore, simplified respirometric tests revealed the variation of biomass activity over long time, proving attached biomass had much higher nitrification activity than suspended biomass, with almost no change after DO dropped to 4mg/L. Meanwhile, the microbial community by 16S rDNA clone library also indicated the accumulation of abundant nitrifiers in the biofilm, supporting the process optimization. The integrated methods of process modeling, biomass activity evaluation and microbial community analysis showed great potential in engineering practice for process optimization.

Cost-Effective Implementation of an Integrated Fixed-film Activated Sludge Process: Accommodating Economic Development for the City of Twin Falls

Cost-Effective Implementation of an Integrated Fixed-film Activated Sludge Process: Accommodating Economic Development for the City of Twin Falls

Nitrifying Bacterial Community Structure of a Full-Scale Integrated Fixed-Film Activated Sludge Process as Investigated by Pyrosequencing

Nitrifying bacterial community structures of suspended and attached biomasses in a full-scale integrated fixed-film activated sludge process were investigated by analyzing 16S rRNA gene sequences obtained from pyrosequencing. The suspended biomass had a higher number of ammoniaoxidizing bacterial sequences (0.8% of total sequences) than the attached biomass (0.07%), although most of the sequences were within the Nitrosomonas oligotropha lineage in both biomasses. Nitrospira-like nitrite-oxidizing bacterial sequences were retrieved in the suspended biomass (0.06%), not in the attached biomass, whereas the existence of Nitrobacter-like sequences was not evident. The suspended biomass had higher nitrification activity (1.13 mg N/TSS/h) than the attached biomass (0.07 mg N/TSS/h). Overall, the results made it possible to conclude the importance of the suspended biomass, rather than the attached biomass, in nitrification in the wastewater treatment process studied.

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.