IFAS Systems Research Articles

Enhanced Nitrogen Removal in a Pilot-Scale Anoxic/Aerobic (A/O) Process Coupling PE Carrier and Nitrifying Bacteria PE Carrier: Performance and Microbial Shift

Integrated fixed-film activated sludge technology (IFAS) has a great advantage in improving nitrogen removal performance and increasing treatment capacity of municipal wastewater treatment plants with limited land for upgrading and reconstruction. This research aims at investigating the enhancing effects of polyethylene (PE) carrier and nitrifying bacteria PE (NBPE) carrier on nitrogen removal efficiency of an anoxic/aerobic (A/O) system from municipal wastewater and revealing temporal changes in microbial community evolution. A pilot-scale A/O system and a pilot-scale IFAS system were operated for nearly 200 days, respectively. Traditional PE and NBPE carriers were added to the IFAS system at different operating phases. Results showed that the treatment capacity of the IFAS system was enhanced by almost 50% and 100% by coupling the PE carrier and NBPE carrier, respectively. For the PE carrier, nitrifying bacteria abundance was maintained at 7.05%. In contrast, the nitrifying bacteria on the NBPE carrier was enriched from 6.66% to 23.17%, which could improve the nitrogen removal and treating capacity of the IFAS system. Finally, the ammonia efficiency of the IFAS system with NBPE carrier reached 73.0 ± 7.9% under 400% influent shock load and hydraulic retention time of 1.8 h. The study supplies a suitable nitrifying bacteria enrichment method that can be used to help enhance the nitrogen removal performance of municipal wastewater treatment plants. The study’s results advance the understanding of this enrichment method that effectively improves nitrogen removal and anti-resistance shock-load capacity.

Efficiency studies of modified IFAS-OSA system upgraded by an anoxic sludge holding tank

An upgraded integrated fixed-film activated sludge-oxic settling anoxic (IFAS-OSA) system is a new technology for reducing nutrients and excess sludge. The results showed that the average TN removal efficiency of the IFAS-OSA system was gradually increased up to 7.5%, while the PO4–3-P removal efficiency increased up-to 27%, compared with that of the IFAS system. The COD removal efficiency of the IFAS-OSA system was slightly increased up-to 5.4% and TSS removal efficiency increased up to 10.5% compared with the control system. Biomass yield coefficient (Yobs) in the IFAS and IFAS-OSA systems were 0.44 and 0.24 (gr MLSS/ gr COD). Hence, sludge production decreased by 45%. The average SVI was decreased by 48% in IFAS-OSA system compared with IFAS. This study demonstrated the better performance of the IFAS-OSA system compared to that of the IFAS system.

Chemical Enhancement for Retrofitting Moving Bed Biofilm and Integrated Fixed Film Activated Sludge Systems into Membrane Bioreactors.

Positive effects of retrofitting MBBR and IFAS systems into MBRs can be exploited by introducing chemical enhancement applying coagulants in the membrane separation step. The current study reports basic principles of chemical enhancement with aluminium sulphate coagulant in biofilm-MBR (Bf-MBR) based on results of total recycle tests performed at different dosages of the chemical enhancer and properties characterization of filtrates, supernatants and sediments. It demonstrates a possibility to achieve lower membrane fouling rates with dosing of aluminium sulphate coagulant into MBBR and IFAS mixed liquors by extending operational cycles by 20 and 80 time respectively as well as increasing operating permeability of membrane separation by 1.3 times for IFAS. It has been found that charge neutralization is the dominating mechanism of aluminium sulphate action as a chemical enhancer in Bf-MBR, however, properties of the membrane surface influencing charge repulsion of foulants should be considered together with the secondary ability of the coagulant to improve consolidation of sediments.

Improving nitrogen removal in an IFAS nitritation–anammox reactor treating lagoon supernatant by manipulating biocarrier filling ratio and hydraulic retention time

A lab-scale integrated fixed-film activated sludge sequencing batch reactor (IFAS-SBR) was established for a one-stage nitritation–anammox process treating lagoon supernatant and optimized by altering both the biocarrier filling ratio and HRT for 500 days. The reactor’s nitrogen removal rate increased slightly from 0.25 kg N m−3 d−1 to 0.29 kg N m−3 d−1 when biocarrier filling ratio was increased from 35% to 55% at a HRT of 2.5 d, and further increased to 0.46 kg N m−3 d−1 and 0.54 kg N m−3 d−1 when the HRT was reduced to 1.5 d and 1.2 d, respectively. Meanwhile, both NH4+N and TN removal efficiencies increased from 81.8% and 74.8% to 95.2% and 87.4%, respectively, with the increased biocarrier filling ratio; however, they decreased slightly to 91.8% and 82.1% at HRT of 1.5 d and to 89.6% and 78.8% at HRT of 1.2 d, respectively. A distinct segregation of anammox bacteria and ammonium oxidizing bacteria (AOB) was achieved in the IFAS system and was highlighted by the decreased HRTs, which also contributed to the excellent nitrogen removal. The specific anammox activity was higher in biofilm than in suspended flocs, and vice versafor the specific AOB activity. The abundance of major microbial communities involved in this process were analyzed, which supported the observation of reactor performance changes. The present study provides critical knowledge for optimizing the one-stage IFAS nitritation–anammox reactor treating supernatant of anaerobically digested sludge thicken lagoon.

An innovative wastewater treatment technology based on UASB and IFAS for cost-efficient macro and micropollutant removal

An innovative process based on the combination of a UASB reactor and an IFAS system is proposed in order to combine different redox conditions and biomass conformations to promote a high microbial diversity. The objective of this configuration is to enhance the biological removal of organic micropollutants (OMPs) as well as to achieve the abatement of nitrogen by using the dissolved methane as an inexpensive electron donor. Results showed high removals of COD (93%) and dissolved methane present in the UASB effluent (up to 85%) was biodegraded by a consortium of aerobic methanotrophs and heterotrophic denitrifiers. Total nitrogen removal decreased slightly along the operation (from 44 to 33%), depending on the availability of electron donor, biomass concentration, and configuration (floccules and biofilm). A high removal was achieved in the hybrid system (>80%) for 6 of the studied OMPs. Sulfamethoxazole, trimethoprim, naproxen, and estradiol were readily biotransformed under anaerobic conditions, whereas ibuprofen or bisphenol A were removed in the anoxic-aerobic compartment. Evidence of the cometabolic biotransformation of OMPs has been found, such as the influence of nitrification activity on the removal of bisphenol A, and of the denitrification activity on ethinylestradiol removal.

The influence of sludge retention time on sludge flocculation in IFAS system

The IFAS system was cultivated in five sequencing batch reactors. The sludge retention times (SRT) were 6 d, 8 d, 10 d, 15 d and 25 d respectively. In this dissertation, the influence of SRT on suspended sludge flocculation in IFAS system and its mechanisms were studied. It was found that in the IFAS system, the specific turbidity of supernatant and SVI value of suspended sludge both decreased as the SRT increased. In addition, extending SRT was capable of reducing the extracellular polymeric substances (EPS) content and the interaction energy barriers, increasing the percentage of bivalent and trivalent cations in pellet, thus improved the sludge flocculation and reduced effluent turbidity.

IFAS Systems with Structured Sheet Media for Simultaneous Carbon Oxidation, Nitrification, Denitrification and Implications

IFAS Systems with Structured Sheet Media for Simultaneous Carbon Oxidation, Nitrification, Denitrification and Implications

Selection of denitrifying phosphorous accumulating organisms in IFAS systems: Comparison of nitrite with nitrate as an electron acceptor

Nitrite and nitrate were compared as electron acceptors to select for denitrifying phosphorous accumulating organisms (DPAO) in two integrated fixed film activated sludge (IFAS 1 and IFAS 2) systems operated as sequencing batch reactors. The bench-scale experiment lasted one year and synthetic wastewater was used as feed. During anoxic conditions 20mgNO3−–NL−1 were dosed into IFAS-1 and 20mgNO2−–NL−1 were dosed into IFAS-2. Long term phosphorous and ammonia removal via nitritation were achieved in both systems and both attached and suspended biomass contributed to phosphorous and ammonia removal. DPAO showed no specific adaptation to the electron acceptor as evidenced by short term switch of feeding with nitrate or nitrite. Anoxic phosphorus uptake rate was significantly higher with nitrite than with nitrate. Results showed that DPAO activity with nitrite could be integrated into attached and suspended biomass of IFAS systems in long term operation.

Assessment of Oxygen Transfer, Uptake and Energy Footprint of Full Scale SSM IFAS Systems using Off-gas Testing

Assessment of Oxygen Transfer, Uptake and Energy Footprint of Full Scale SSM IFAS Systems using Off-gas Testing

Nitrification and denitrification using biofilters packed with sulfur and limestone at a pilot-scale municipal wastewater treatment plant

A pilot-scale municipal wastewater treatment plant composed of a fixed film activated sludge (IFAS) system with sulfur–limestone autotrophic denitrification (SLAD) was operated for a year and the influence of different operational factors was investigated. Nitrification efficiency was found to be above 91% at temperatures above 25°C even at short hydraulic residence times (HRTs), but declined to 51±2% when the temperature dropped to 22±3°C. The minimum HRT (HRTmin) to achieve nitrification efficiency>90% was found to be 12 h at temperatures above 25°C. Denitrification efficiencies were found to be 89% and 79% at a nitrate loading of 0.36 kg NO-N m−3 d−1 and at 0.18 kg NO-N m−3 d−1, respectively. The minimum empty bed residence time (EBRT) to achieve denitrification efficiency above 80% without methanol addition was 3 h at a nitrate loading rate of 0.27–0.38 kg NO-N m−3 d−1. The amount of nitrate removed as a function of the sulfate formed was found to be 0.188 g NO-N/g SO. The nitrate load removed by the biofilter as a function of the alkalinity consumed was found to be very close to the theoretical stoichiometric value. The application of the pilot plant was proven to be feasible and the performance of the SLAD system, especially with respect to the minimum EBRT to achieve denitrification efficiency above 80%, the maximum denitrification rate and performance at temperatures below 10°C. To achieve a nitrification efficiency above 90% in the IFAS system, temperature changes and the minimum HRT were found to be the most influential operational parameters.

Modeling A Full-Scale IFAS System in Groton, CT

Mathematical modeling was used to analyze a full-scale IFAS installation in Groton, CT. The model was calibrated at steady-state using historical plant data from early 2009. Simulation investigations allowed plant managers to assess the capacity of the IFAS system under average and peak loadings. Several scenarios for taking older secondary clarifiers off-line for repair were simulated. A planned carbon addition test was simulated in advanced to confirm the correct dosage and expected time to achieve the expected denitrification performance improvement.

Improving our Understanding of the Differences between Fixed and Moving Bed Media IFAS Systems for Design, Operations and for Real Time Control of Plants (in Aquifas+) to Simultaneously Enhance Nutrient Removal and Minimize GHG Emissions

Improving our Understanding of the Differences between Fixed and Moving Bed Media IFAS Systems for Design, Operations and for Real Time Control of Plants (in Aquifas+) to Simultaneously Enhance Nutrient Removal and Minimize GHG Emissions

Full Scale Implementation, Operation, and Performance of a Structured Sheet Media IFAS System

Full Scale Implementation, Operation, and Performance of a Structured Sheet Media IFAS System

Pilot Study Confirms Design of IFAS System for Nitrogen Reduction in Connecticut

Pilot Study Confirms Design of IFAS System for Nitrogen Reduction in Connecticut

BioWin Modeling of a Three Reactor IFAS System

BioWin Modeling of a Three Reactor IFAS System

The Importance of Aerobic Mixing, Biofilm Thickness Control and Modeling on the Success or Failure of IFAS Systems for Biological Nutrient Removal

The Importance of Aerobic Mixing, Biofilm Thickness Control and Modeling on the Success or Failure of IFAS Systems for Biological Nutrient Removal

Detachment of Solids and Nitrifiers in IFAS Systems

Detachment of Solids and Nitrifiers in IFAS Systems

UNDERSTANDING THE IMPORTANCE OF AEROBIC MIXING, BIOFILM THICKNESS CONTROL AND MODELING ON THE SUCCESS OR FAILURE OF IFAS SYSTEMS FOR BIOLOGICAL NUTRIENT REMOVAL

Research was conducted in IFAS systems to identify problems that arose with the biofilm when the intensity of mixing and aeration fall below or rise above certain thresholds. The types of IFAS media evaluated include fixed bed cord media (Ringlace and Bioweb), moving bed sponge (sponge media – Linpor and Captor; and plastic media – Kaldnes) and RBC media. An aeration process design model and operating strategies have been developed to address these problems. This paper presents the IFAS and MBBR design methodology and aeration process design component of the Aquifas Unified Model for Activated Sludge, IFAS and MBBR systems. The paper references specific instances in full-scale IFAS plants where problems occurred because of insufficient or improper mixing patterns and documents how they were resolved. The problems observed included nuisance predator development and plugging of media and screens. The IFAS model was upgraded to incorporate computation of biofilm thickness and the impact of the increase in biofilm thickness on the reduction in effective surface area available on a various types of media. Effective surface area is the m 2 of biofilm surface per m 3 of tank volume. The model uses the effective surface area and the amount of media in the tank to compute the substrate (COD, NH4N and Oxidized-N) profiles. Additional research is being conducted to establish certain thresholds for mixing necessary above and beyond the aeration requirements to maintain a thin biofilm. The paper shows how the process design model is applied to improve the design of IFAS and MBBR systems. In instances where the aeration requirement to satisfy the DO set-point is satisfied but the mixing is below the threshold to maintain a thin biofilm, the media fill volume fraction in an aerobic cell can be increased and the fraction of tank volume occupied by the aerobic cell can be increased. By increasing the media fill volume fraction in a situation where the biofilm in an aerobic cell is too thick, the total amount of biofilm surface area present in the aerobic cell is increased and the soluble COD concentration is decreased. This decreases the biofilm thickness observed for the same intensity of mixing and increases the effective surface area of biofilm. This improves the performance of the system. When the media fill volume fraction is increased, the air flow per unit of reactor volume has to be increased to satisfy the additional oxygen demand. This increase in air flow helps satisfy the mixing requirements to mix the media and induce the requisite amount of biofilm shear. In some instances with fixed bed media, supplemental aeration system is installed below the frames to increase the air flow during diurnal peak load hours and thin out the biofilm.