Fixed-film Activated Sludge System Research Articles

Enhancing simultaneous nitrification and denitrification in a plant-scale integrated fixed-film activated sludge system: Focusing on the cooperation between activated sludge and biofilm

To further remove nutrients through simultaneous nitrification and denitrification (SND), the integrated fixed-film activated sludge (IFAS) system has become one of the most efficient pathways for modifying the existing wastewater treatment plants. This study investigated the cooperation between suspended activated sludge and carrier-attached biofilm for promoting SND in different seasons in a plant-scale IFAS system. The results showed that the involvement of biofilm could stimulate SND, removing 23.9 % of influent total nitrogen (TN) in the aerobic IFAS system. The nitrification rate and the SND ratio were much influenced by the temperature, resulting in higher TN removal efficiency in summer (90.3 %) than that in winter (86.4 %). The highest SND ratio of 67 % could be achieved at the temperature of 23 °C. Additionally, the SND ratio also depended on a variety of operational parameters (such as dissolved oxygen (DO), COD/NH4+-N, and mixed liquor suspended solids (MLSS)). High-throughput sequencing technology further confirmed that the composition of the functional bacterial communities in activated sludge significantly differed from that in biofilm. Nitrifying bacteria were mostly detected in biofilm samples, while more denitrifying bacteria existed in activated sludge, thus resulting in the enhancement of synergic nitrogen removal via SND in the IFAS system.

Integrated fixed-film activated sludge systems in continuous-flow and batch mode acclimated from low to high aniline concentrations: Performance, mechanism and metabolic pathways

Integrated fixed-film activated sludge (IFAS) system has considerable advantages in treating aniline wastewater economically and efficiently. However, the response mechanism of IFAS to aniline needs further study. Herein, IFAS in continuous-flow (CF-IFAS) and batch mode (B-IFAS) were set up to investigate it. The removal efficiency of aniline exceeded 99% under different stress intensities. At low stress intensity (aniline ≈ 200 mg/L), the total nitrogen removal efficiency of B-IFAS was approximately 37.76% higher than CF-IFAS. When the stress intensity increased (aniline ≥ 400 mg/L), both were over 82%. CF-IFAS was restrained by denitrification while nitrification in B-IFAS. The legacy effect of perturbation of B-IFAS made microflora quickly reach new stability. The closer interspecific relationship in B-IFAS and more key species: Leucobacter, Rhodococcus, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Ellin6067 and norank_f_NS9_marine_group. Metabolic and Cell growth and death were the most abundant metabolic pathways, resulting both systems the excellent pollutant removal and stability under high stress intensity.

Morphological and Spatial Heterogeneity of Microbial Communities in Pilot-Scale Autotrophic Integrated Fixed-Film Activated Sludge System Treating Coal to Ethylene Glycol Wastewater.

The understanding of microbial compositions in different dimensions is essential to achieve the successful design and operation of the partial nitritation/anammox (PN/A) process. This study investigated the microbial communities of different sludge morphologies and spatial distribution in the one-stage PN/A process of treating real coal to ethylene glycol (CtEG) wastewater at a pilot-scale integrated fixed-film activated sludge (IFAS) reactor. The results showed that ammonia-oxidizing bacteria (AOB) was mainly distributed in flocs (13.56 ± 3.16%), whereas anammox bacteria (AnAOB) was dominated in the biofilms (17.88 ± 8.05%). Furthermore, the dominant AnAOB genus in biofilms among the first three chambers was Candidatus Brocadia (6.46 ± 2.14% to 11.82 ± 6.33%), whereas it was unexpectedly transformed to Candidatus Kuenenia (9.47 ± 1.70%) and Candidatus Anammoxoglobus (8.56 ± 4.69%) in the last chamber. This demonstrated that the niche differentiation resulting from morphological (dissolved oxygen) and spatial heterogeneity (gradient distribution of nutrients and toxins) was the main reason for dominant bacterial distribution. Overall, this study presents more comprehensive information on the heterogeneous distribution and transformation of communities in PN/A processes, providing a theoretical basis for targeted culture and selection of microbial communities in practical engineering.

The Nitrogen Removal Performance and Microbial Community of Integrated Fixed-Film Activated Sludge Systems with Carriers

The Nitrogen Removal Performance and Microbial Community of Integrated Fixed-Film Activated Sludge Systems with Carriers

Occurrence of aerobic denitrifying bacteria in integrated fixed film activated sludge system

Denitrification can be enhanced in the Integrated Fixed Film Activated System (IFAS) system by integrating media into the anoxic or aerobic zone. The simultaneous nitrification and denitrification (SND) in the biofilm layers has been reported in the aerobic zone of the IFAS system. In this study, two IFAS systems with Bioweb® media installed in the anoxic or aerobic reactor were operated in parallel to evaluate both anoxic denitrification or aerobic SND in the biofilm layers enhanced by fixed film media at three different nitrite and nitrate recirculation (NR) ratios of 75%, 100%, and 125%. The results revealed that both IFAS systems achieved the same organic and nitrogen removal efficiencies without statistically significant difference. The NR ratio of 125% enhanced slightly the denitrification in the anoxic zones of both systems. The media increased the anoxic denitrification at the NR ratio of 100%. The SND in the biofilm was found insignificant in both systems. It was evident that suspended-growth microorganisms stored substrates internally in the cells under anoxic conditions due to insufficient retention time. The aerobic denitrifiers including Chryseobacterium sp., Klebsiella pneumonia, and Pseudomonas aeruginosa were abundant in both IFAS systems providing aerobic denitrification with storage products as carbon sources. In summary, the denitrification in the anoxic zone and SND in the biofilm of the aerobic zone, both were enhanced by the fixed film media, did not contribute significantly to the IFAS system for the biological nitrogen removal because of microbial storage products and aerobic denitrification of several aerobic denitrifiers.

Effects of pH on extracellular polymeric substances compositions of biofilm in Integrated Fixed Film Activated Sludge process

Integrated fixed film activated sludge system typically integrates biofilm in the aerobic zone. The proteins-to-polysaccharides ratio of extracellular polymeric substances in the biofilm matrix is related to the strength of biofilm and, thereby, involves with the reliability and performance of this system. This study evaluated the effects of pH on proportions of both components in the extracellular polymeric substances of biofilm installed in the aerobic zone of this system. The experiments were conducted in four identical pilot-scale activated sludge systems, by which three systems were installed with Bioweb® media in the aerobic zones and fed with different wastewater pH values of 6.5, 7.5 and 8.5, respectively. Another system without fixed film media installed was fed with influent pH of 7.5 and then used as a control system. It was found that the proteins-to-polysaccharides ratios of the extracellular polymeric substances in biofilm were 0.12, 0.10 and 0.08 (w/w) at the influent pH values of 6.5, 7.5 and 8.5, respectively. The ratios decreased as the influent pH increased from 6.5 to 8.5, suggesting that extracellular polymeric substances were loosely structured in biofilm layers. Less proteins with more polysaccharides were found at high pH of 8.5, leading to resulting in the easily detachment of biofilm and viscous bulking of suspended flocs. Loosely structured biofilm decreased the mass transfer resistances, resulting in higher denitrification and nitratation in aerobic zones; therefore, the highest biological nitrogen removal was achieved at the pH of 8.5.

Fate of pharmaceutically active compounds in a pilot-scale A2O integrated fixed-film activated sludge (IFAS) process treating municipal wastewater

The goal of this research was to study the operation of an integrated fixed-film activated sludge system (IFAS), in anaerobic/anoxic/aerobic (A2O) configuration for the elimination of emerging pollutants, in particular of 27 pharmaceutical active compounds (PhACs) (eight anti-inflammatory and/or analgesic pharmaceuticals (AIAPs), six antibiotics, four b-blockers, two antihypertensives/diuretics, three lipid regulators-bezafibrate and four psychiatric medications). Different operational conditions were analyzed in the biological reactor, controlling at all times both the amount of suspended and fixed biomass present. The A2O-IFAS system has obtained similar or higher removal efficiency (RE) in the elimination of organic matter, and especially of nutrients, nitrogen (N) and phosphorous (P), with respect to the conventional A2O system, working however with very low values of the sludge retention time (SRT) (4.0 days) and mix liquid suspended solid (MLSS) in the reactor (1822 mg L-1). In general, conventional activated sludge (CAS) and IFAS processes show the importance of operating at high SRT and MLSS concentration, that give low food/microorganisms (F/M) ratio, to increase the RE of several PhACs. However, the A2O-IFAS system, operating with low mixed liquor SRT and MLSS has achieved similar or better RE of PhACs, obtaining the highest average REs values (>80%) for fenofibrate, acetaminophen, ibuprofen, naproxen, clarithromycin and atenolol. According to the results obtained, due to the affordable cost and well-demonstrated performance, IFAS systems become one of the most promising technology for conventional wastewater treatment plants (WWTP) upgrading.

Effect of Carrier Filling Ratios on Dissolved Organic Nitrogen Removal in Integrated Fixed-Film Activated Sludge Systems Treating Municipal Wastewater

Previous research has focused on the removal characteristics of inorganic nitrogen in the integrated fixed-film activated sludge (IFAS) process. However, information on dissolved organic nitrogen (...

Loofah Sponges as Bio-Carriers in a Pilot-Scale Integrated Fixed-Film Activated Sludge System for Municipal Wastewater Treatment

Fixed-film biofilm reactors are considered one of the most effective wastewater treatment processes, however, the cost of their plastic bio-carriers makes them less attractive for application in developing countries. This study evaluated loofah sponges, an eco-friendly renewable agricultural product, as bio-carriers in a pilot-scale integrated fixed-film activated sludge (IFAS) system for the treatment of municipal wastewater. Tests showed that pristine loofah sponges disintegrated within two weeks resulting in a decrease in the treatment efficiencies. Accordingly, loofah sponges were modified by coating them with CaCO3 and polymer. IFAS pilot tests using the modified loofah sponges achieved 83% organic removal and 71% total nitrogen removal and met Vietnam’s wastewater effluent discharge standards. The system achieved considerably high levels of nitrification and it was not limited by the loading rate or dissolved oxygen levels. Cell concentrations in the carriers were twenty to forty times higher than those within the aeration tank. Through 16S-rRNA sequencing, the major micro-organism types identified were Kluyvera cryocrescens, Exiguobacterium indicum, Bacillus tropicus, Aeromonas hydrophila, Enterobacter cloacae, and Pseudomonas turukhanskensis. This study demonstrated that although modified loofah sponges are effective renewable bio-carriers for municipal wastewater treatment, longer-term testing is recommended.

Simultaneous nitrogen and dissolved methane removal from an upflow anaerobic sludge blanket reactor effluent using an integrated fixed-film activated sludge system

One of the main drawbacks of upflow anaerobic sludge blanket (UASB) reactors that treat low-strength sewage at room temperature is related to the low quality of their effluents in terms of dissolved methane, organic matter, and nitrogen content. The present study aims to evaluate the feasibility of using an integrated fixed-film activated sludge (IFAS) system as an alternative post-treatment technology to mitigate the environmental impact of such effluents. For this purpose, a pilot plant composed of a UASB (120 L) followed by an IFAS (66 L) system was operated for 407 days. Special attention was paid to the suspended biomass retention capacity and the dissolved methane and nitrogen removal potential of the IFAS post-treatment system. Furthermore, the role of carriers on denitrification and nitrification processes and the microbial communities present in the biofilm were also analyzed. Average total chemical oxygen demand (CODT) and ammonium removal efficiencies of 92 ± 3% and around 57 ± 16% were attained throughout the entire operation, respectively. During a first period in which biomass was maintained in both biofilms and suspension, and nitrite was the main electron acceptor, maximum nitrogen removal and methane removal efficiencies of 32.5 mg TN L-1 and 93% were observed in the IFAS system, respectively. However, throughout the second period, in which suspended biomass was completely washed out from the IFAS system, and nitrate became the main electron acceptor, these values decreased to 18 ± 4 mg TN Lfeed-1 and 77 ± 12%, respectively. Surprisingly, throughout the entire operation, it was observed that around 50 and 41% of the total nitrogen and methane removals observed in the IFAS system, respectively, were carried out in the aerobic compartment. Aerobic methane oxidizers and anammox were detected with significant relative abundances in the biofilm carriers used in the anoxic and aerobic compartments using 16S rRNA gene amplicon sequencing analysis. Therefore, the use of an IFAS system could be suited to diminish greenhouse gas emissions and nutrients concentration for those sewage treatment plants that used UASB systems, especially in countries with temperate and warm climates.

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.

Upgrading Conventional Activated Sludge System Using Bio-media: A Case Study of Zenin Wastewater Treatment Plant, Egypt

This study investigated the ability to upgrade the biological treatment system in Zenin wastewater treatment plant, in Egypt. This investigation was conducted through the comparison of three different biological treatment systems: activated sludge process (AS), moving bed biofilm reactor (MBBR), and integrated fixed film activated sludge system (IFAS). Three pilot systems were established at Zenin wastewater treatment plant, to simulate AS, MBBR, and IFAS systems, to show the effect of various parameters on the removal efficiencies of biochemical oxygen demand (BOD 5 ), total suspended solids (TSS), and ammonium-nitrogen (NH 4 -N). Different values of hydraulic retention time, different amounts of returned sludge, and concentration of dissolved oxygen, were examined. The maximum removal efficiencies of BOD 5 , TSS, and NH 4 -N were 50%, 81.9%, and 82% in activated sludge system, respectively; 80%, 81.8%, and 99.3% in MBBR system, respectively; and 62.3%, 86.2%, and 76% in IFAS system, respectively. Keywords: Attached growth; Hybrid growth; Sludge; Suspended growth; Wastewater DOI : 10.7176/CER/11-1-05

The role of interactions of effective biofilm surface area and mass transfer in nitrogen removal efficiency of an integrated fixed-film activated sludge system

A reaction-diffusion biofilm model was implemented to simulate the nitrification/denitrification performance of a lab-scale integrated fixed-film activated sludge (IFAS) reactor. The model was capable of representing the system performance, i.e. changes in organic load and decrease in sludge age. Furthermore, nitrification batch tests with sludge and carrier material could also be simulated successfully with the model. Model simulation revealed that the diffusive fluxes into biofilm depended strongly on substrate loading as well as sludge age. The microbial composition in the biofilm matrix was mainly influenced by the diffusive flux of chemical oxygen demand (COD) into biofilm. When COD removal started to switch to biofilm, heterotrophic bacteria quickly replaced the previously dominating autotrophic bacteria. Running a set of simulations with a range of effective biofilm surface area and different mass transfer coefficients revealed the strong influence of these two parameters on the IFAS performance. The analysis showed that both parameters were dominating factors for ammonium removal. The optimum mass transfer coefficient was in the range of 3–4 m d−1 and the effective biofilm surface was around 63–88% of the theoretical carrier surface.

Determination of Kinetic Parameters in Integrated Fixed Film Activated Sludge for Amol's Industrial Park Wastewater Treatment Plant

In this study the performance of integrated fixed film activated sludge system (IFAS) in Amol industrial wastewater treatment plant (Amol, Iran) in treatment of food industrial wastewater was investigated. In addition, kinetic coefficients were evaluated for the system. The capacity of this system was 1700 cubic meters per day; that includes different process comprising physical and biological treatment, disinfection, sludge thickening, digestion and dewatering. COD removal efficiency and kinetic coefficients including yield coefficient (Y), half saturation coefficient (Ks), maximum substrate utilization rate constant (k) and endogenous decay coefficient (kd) were evaluated. The obtained results demonstrated that except Ks other coefficient were in the normal range that was frequently reported for conventional activated sludge in the literature. The COD removal efficiency was about 98 to 99 percent. The results indicated that there is a direct relationship between the variation of kd and Ks with effluent substrate concentration; while, the relationship between rate constant (k) and effluent COD is reversed. Finally, the effect of increasing sludge retention time (SRT) on COD removal was also studied. It was concluded that COD removal increased with an increase active solid retention time to a certain point, behind that point there was no significant changes observed.

Temporal dynamics of the microbial community in an integrated fixed-film activated sludge system revealed by 16S rRNA MiSeq sequencing

Temporal dynamics of the microbial community in an integrated fixed-film activated sludge system revealed by 16S rRNA MiSeq sequencing

Validating the Colloid model to optimise the design and operation of both moving-bed biofilm reactor and integrated fixed-film activated sludge systems

The paper presents a systematic study of simulations, using a previously calibrated Colloid model, from which it was found that: (i) for pure moving-bed biofilm reactor (MBBR) processes with tertiary nitrification conditions (no influent chemical oxygen demand (COD)), dissolved oxygen = 5 mg/L and residual NH4-N > 4 mgN/L, a nitrification rate of 1.2 gN/(m(2)d) was obtained at 10 °C. This rate decreases sharply when residual NH4-N is lower than 2 mgN/L, (ii) for MBBR systems with predenitrification-nitrification zones and COD in the influent (soluble and particulate), the nitrification rate (0.6 gN/(m(2)d)) is half of that in tertiary nitrification due to the effect of influent colloidal XS (particulate slowly biodegradable COD) and (iii) for integrated fixed-film activated sludge (IFAS) processes the nitrification rate in the biofilm (0.72 gN/(m(2)d)) is 20% higher than for the pure MBBR due to the lower effect of influent XS since it is adsorbed onto flocs. However, it is still 40% lower than the tertiary nitrification rate. In the IFAS, the fraction of the nitrification rate in suspension ranges from 10 to 70% when the aerobic solids retention time varies from 1.4 to 6 days.

Performance and microbial characteristics of integrated fixed-film activated sludge system treating industrial wastewater

Integrated fixed-film activated sludge (IFAS) is a modification of conventional activated sludge processes used for wastewater treatment consisting of biofilm attachment surfaces added to suspended-growth reactors, thereby creating hybrid suspended attached-growth systems. In this work, an IFAS system, with a total working volume of 560.7 L, was employed to investigate the performance of pollutants removal in industrial effluent. Microbial communities of suspended-growth and attached-growth biomass were investigated by a combination of polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and fluorescence in situ hybridization (FISH). In the system, suspended-growth and attached-growth biomass worked together to maintain a stable COD, NH₄(+)-N and TN removal efficiency of 74, 93 and 76%, respectively. PCR-DGGE results showed that Proteobacteria was the dominant genera of bacteria in both the suspended and attached growth sludge. Some of the bacterial species (Firmicutes and Pseudomonas) may play an important role in the organic degradation of this water. Denitrifying bacteria were found to be accumulated in the biofilms. FISH results showed that there were more nitrifying bacteria in the suspended-growth biomass than the attached-growth biomass but fewer denitrifying bacteria in the former biomass.

Structural, physicochemical and microbial properties of flocs and biofilms in integrated fixed-film activated sludge (IFFAS) systems

Integrated fixed-film activated sludge systems (IFFAS) may achieve year-round nitrification or gain additional treatment capacity due to the presence of both flocs and biofilms, and the potential for multiple redox states and long solids retention time. Flocs and biofilms are distinctive microbial structures and characterization of the physicochemical and structural properties of these may provide insight into their respective roles in wastewater treatment and contaminant removal in IFFAS. Flocs and biofilms were examined from five different pilot media systems being evaluated for potential full scale implementation at a large municipal wastewater treatment plant. Flocs and biofilms within the same system possessed different surface characteristics; flocs were found to have a higher negative surface charge (−0.35 to −0.65 meq./g VSS) and are more hydrophobic (60%–75%) than biofilms (−0.05 to −0.07 meq/g VSS; 19–34%). The EPS content of flocs was significantly higher (range of 2.1–4.5 folds) than that of biofilms. In floc-derived extracellular polymeric substances (EPS), protein (PN) was clearly dominant; whereas in biofilm-derived EPS, PN and polysaccharide (PS) were present in approximately equal proportions. Biofilm EPS had a higher proportion of DNA when compared to flocs. Biofilm growth was preferential on the protected internal surfaces of the media. Colonization of the external surfaces of the media was evident by the presence of small microcolonies. The structural heterogeneity of the biofilms examined was supported by observed differences in biomass content, thickness and roughness of biofilm surface. The biofilm on the interior surface of media was found to be patchy with clusters of cells connected by an irregular arrangement of interconnecting EPS projections. Biofilm thickness ranged between 139 μm and 253 μm. The pattern of oxygen penetration is expected to be complex. Nitrifiers and denitrifiers were predominantly associated with the biofilms, and the latter were found to be dispersed throughout the film and arranged in micro-clusters, suggesting partial oxygen penetration.

Integrated Fixed Film Activated Sludge Systems for upgrading Hydraulic Capacity and Settling Characteristics of Activated Sludge Processes

In this research an experimental laboratory pilot plant was used to assess the ability of the integrated fixed film activated sludge (IFAS) process to upgrade the hydraulic capacity of the ordinary activated sludge units. The experimental plant consisted of three basins, which were designed to work simultaneously under the same operating conditions. The second and third basins were developed to work on the suggested process by adding a fixed media to these reactors in such way so that the specific area in the second basin was 18.72 m2/m3 and in the third 37.44 m2/m3. The experimental program was divided into five stages so that, the applied discharges in the second, third, fourth and fifth stages were 150%, 200%, 250% and 300% of the discharge in the first stage respectively. The result of the experimental work showed that the (IFAS) process can effectively upgrade the capacity and performance of the ordinary activated sludge process. In the second basin, the discharge was increased to about 125 % of its original value without reduction in the organic removal efficiency while, in the third basin the load increased to 150 % of its original value and also no reduction in the removal efficiency was observed. The settling characteristics of the activated sludge also improved and filamentous growth became very limited.

Nitrification and Denitrification in an Aerobic Integrated Fixed-Film Activated Sludge System

Nitrification and Denitrification in an Aerobic Integrated Fixed-Film Activated Sludge System