Fixed-film Reactor Research Articles

Biofilm characterization and dynamic simulation of advanced rope media reactor for the treatment of primary effluent.

Biofilm modeling is inherently complex, often requiring multiple assumptions and simplifications. In biofilm modeling, default or literature-based values in biofilm systems are usually used to estimate biofilm parameters, including boundary layer, biofilm density, thickness, attachment, and detachment rates. This study aimed to characterize and model the biofilm of a specific rope-type fixed media system, removing carbon and total inorganic nitrogen, coupled with sensitivity analysis. Among the five model parameters, the sensitivity analysis of this study showed that boundary layer thickness is the most influential parameter for predicting effluent ammonia and nitrate concentrations, and biofilm density is most sensitive with respect to effluent chemical oxygen demand (COD). The least sensitive parameter is the detachment rate. Based on the calculated mean absolute error (MAE) and root mean squared error (RMSE), the calibrated BioCord fixed-film reactor (BFFR) model accurately predicted effluent ammonium and dissolved oxygen (DO) in the continuously aerated bench-scale reactor (R1) and failed to predict well in the intermittently aerated bench-scale reactor (R2). RMSE values calculated for NH3-N and DO in R1 are 0.95 and 0.53 mg/L, respectively. In the BioCord pilot plant's case, ammonium-N predicted by the model fit the measured values well, while it overpredicted DO concentrations. PRACTITIONER POINTS: Fixed biofilm BioCord reactors were studied for primary effluent treatment. A methodology was developed to characterize biofilms. Boundary layer thickness is the most influential parameter for predicting effluent ammonia and nitrate concentrations. Biofilm density is the most sensitive parameter with respect to effluent COD. The calibrated BFFR model can predict effluent ammonium, nitrite, and nitrate-nitrogen.

Microbial Biomass in Mesophilic and Thermophilic High-Rate Biodigestion of Sugarcane Vinasse: Similar in Quantity, Different in Composition

This study compared the behavior of the biomass in two fixed-film anaerobic reactors operated under equivalent organic loading rates but at different temperatures, i.e., 30 °C (RMM) and 55 °C (RMT). The reactors were fed with sugarcane vinasse and molasses (both fermented) in a simulation of sequential periods of season and off-season. The dynamics of biomass growth and retention, as well as the microbial composition, were assessed throughout 171 days of continuous operation, coupled with an additional 10-day test assessing the microbial activity in the bed region. Despite the different inoculum sources used (mesophilic granular vs. thermophilic flocculent sludge types), the biomass growth yield was identical (0.036–0.038 g VSS g−1COD) in both systems. The retention rates (higher in RMT) were regulated according to the initial amount of biomass provided in the inoculation, resulting in similar amounts of total retained biomass (46.8 vs. 43.3 g VSS in RMT and RMM) and biomass distribution patterns (30–35% in the feeding zone) at the end of the operation. Meanwhile, hydrogenotrophic methanogenesis mediated by Methanothermobacter coupled to syntrophic acetate oxidation prevailed in RMT, while the Methanosaeta-mediated acetoclastic pathway occurred in RMM. The results show that different anaerobic consortia can behave similarly in quantitative terms when subjected to equivalent organic loads, regardless of the prevailing methane-producing pathway. The community grows and reaches a balance (or a given cell activity level) defined by the amount of substrate available for conversion. In other words, while the metabolic pathway may differ, the endpoint (the amount of biomass) remains the same if operational stability is maintained.

Evaluation of the optimum conditions of an anaerobic Down-flow Stationary Fixed Film reactor for swine wastewater treatment

The Down-flow Stationary Fixed Film (DSFF) reactor is a downstream anaerobic reactor combined with a fixed layer of adhesive media that is capable of handling large organic loads, has cheap investment costs, and has a shorter treatment time than other conventional anaerobic technologies. In this study, the DSFF reactor was used to investigate its potential to remove contaminants from swine wastewater. The optimal operating conditions of the DSFF reactor including hydraulic retention time (HRT), organic concentration, and nutrient ratio were investigated. The obtained results showed that the COD removal efficiency increased from 50% to 79.721% when the influent COD enhanced from 500 to 3000 mg/L. The COD removal efficiency was 85.66%, 61.71% and 50.81% at three different nutritional ratios of C/N/P:250/1.5/1, C/N/P:250/7.5/1, and C/N/P:250/7.5/0.2, respectively. The overall results revealed that the optimal HRT is 12 hours, the optimal COD concentration is between 2000 mg/L and 3000 mg/L, and the optimal nutrient ratio is C/N/P:250/1.5/1. The DSFF reactor effectively manages BOD and phosphorus removal while handling a range of contamination levels in swine wastewater. Furthermore, there is no significant sludge loss and the operation mode is simple. This reactor is potentially appropriate for implementation in pig farming households.

Performance and life cycle assessment of moving-bed biofilm and integrated fixed-film reactors to upgrade activated sludge systems

Upgrading the capacity of existing wastewater treatment plants (WWTPs) is hindered by the limited space for extension. This matter is particularly crucial in developing countries where dense urban areas experience unexpectedly growing populations. Herein, we study the capacity upgrading of a WWTP working by a conventional activated sludge (CAS) system from 180,000 m3/d to 240,000 and 300,000 m3/d. The WWTP case study focuses on a large plant in Mansoura, Egypt, requiring capacity upgrades to accommodate population growth. For this purpose, we used mathematical modeling to simulate current and suggested WWTP designs. Moving bed biofilm reactor (MBBR) and integrated fixed film-activated sludge (IFAS) systems were designed to increase the WWTP capacity to 240,000 and 300,000 m3/d by the addition of plastic biofilm carrier to 25% and 50% of the aeration basins, respectively. IFAS outperformed conventional and MBBR systems in terms of BOD, COD, TSS, NH4, TP, and PO4, in addition to increased capacity. We moreover used life cycle assessment (LCA) to comprehend the environmental favorability of upgrading scenarios. The most affected environmental categories are global warming and eutrophication due to the operation stage (especially electricity). Global warming potential for CAS, MBBR, and IFAS (300,000 m3/d) are 2.19, 1.69, and 1.73 kg CO2 eq respectively. Eutrophication potential for CAS, MBBR, and IFAS (300,000 m3/d) are 0.0025, 0.0022, and 0.0017 kg PO4- eq respectively. We also estimated the amortization and running costs for various upgrading scenarios, providing an integrated analysis for decision-making purposes.

Needle-Felt Coir fibre: A natural substitute for synthetic media in anaerobic fixed film reactors for wastewater treatment

In the past, studies have been conducted to evaluate different materials as filter media during anaerobic treatment of wastewater. The present study aims to assess the viability of using needle-felt coir fibre as a biofilm carrier in an anaerobic baffled reactor for organic-rich wastewater treatment. Real wastewater from a canteen with chemical oxygen demand (COD) - 1400±560 mg/L, and suspended solids (SS) - 397±23 mg/L after stabilization was treated for six months in a pilot scale unit with the carrier medium. The high porosity (90%) and specific surface area (1450±299 m2/m3) of the medium enabled COD (66%) and SS (70.5%) removal along with biogas recovery, at a lower hydraulic retention time of 14 hrs. The metagenomic sequence analysis revealed rich and diverse bacteria and methanogenic archaea in the carrier medium and settled sludge. Compared to the commonly used synthetic media, the needle-felt coir fibre carrier has technical, environmental, and economic advantages. Therefore, needle-felt coir fibre might be a sustainable replacement for conventional synthetic media in anaerobic wastewater treatment systems.

Polyurethane as an alternative support media to low-density polyethylene in fermentative-sulfidogenic reactors: Beneficial or indifferent?

Sporadically addressed in previous studies, the removal of sulfate during fermentation has been a matter of great interest in new applications of fixed-film two-stage biodigestion as the most efficient strategy to boost methane production from a low-sulfate fermented substrate. This study assessed the use of polyurethane (PU) as the support material in a thermophilic (55 °C) fermentative/sulfidogenic fixed-film reactor subjected to different operating conditions based on the variation of the sulfate loading rate (SLR = 8.0–4.0 kg-SO42− m−3 day−1), HRT (12.0–16.0 h) and liquid upflow velocity (3.42–7.90 m h−1). A maximum sulfate removal efficiency of only 46.8 % was achieved when applying SLR and HRT of 4.0 kg-SO42− m−3 day−1 and 16.0 h, respectively, reaching a total dissolved sulfide concentration of 275 mg L−1. This poor performance resulted from two factors: the interspaced arrangement of PU pieces and the use of ethanol as the only carbon source. While the first triggered excess biomass accumulation, the latter favored the establishment of a very restricted microbial community. Only some Clostridia-like bacterial classes, Proteobacteria, and other non-SRB bacteria belonging to phyla Synergistetes and Thermotogae were identified. Hence, under the studied conditions, using PU did not enhance sulfidogenesis in the fermentative reactor.

Luffa cylindrica (Sponge Gourd) Fibers in Treatment of Greywater: an Aerobic Fixed-Film Reactor Approach.

The need for potable water consumption in urban and suburban regions can be decreased by greywater treatment and its reuse. Utilizing natural fibers may provide sustainable solutions in addressing challenges related to water resource management. In this study, a fixed-film reactor was designed with Luffa cylindrica (an annually occurring fruit) as a bio-carrier. The lab-scale reactors were configured with and without Luffa cylindrica and were run for 90days in fed-batch mode. Scanning electron microscopy (SEM) was performed to validate biofilm production over time. Monitoring COD, nitrogen, and total phosphate removal allowed for analysis of treatment effectiveness. Results demonstrated the treatment efficiency for the experimental reactor was 70.96%, 97.02%, 92.57%, and 81.20% for COD, nitrogen, phosphate, and anionic surfactant (AS), respectively. 16s rRNA gene sequencing of bio-carrier and control greywater samples was carried out. Many bacteria known to break down anionic surfactants were observed, and microbial succession was witnessed in the control reactor vs. the experimental reactor samples. The three most prevalent genera in the experimental samples were Chlorobium, Chlorobaculum, and Terrimonas. However, it is crucial to underscore that additional research is essential to solidify our understanding in this domain, with this study laying the fundamental groundwork.

Reaching the operating limit of the continuous multiple tube reactor: Still a promising technology for maximizing fermentative biohydrogen production?

This study simulated the application of the continuous multiple tube reactor (CMTR), a promising technology capable to replace fixed-film reactors in biohydrogen (bioH2) production via dark fermentation, in the processing of sucrose-rich wastewater (COD of up to 16 g L−1). The long-term impacts on both the bioH2 evolution and the dynamics of biomass growth and retention were assessed, aiming to identify the operating limits of the reactor. The bioH2 production was maximized (1445 NmL H2 L−1 d−1) when using moderately concentrated wastewaters (COD = 8 g L−1) at an OLR of 48.0 g COD L−1 d−1, with much lower hydrogenogenic activity (< 200 NmL H2 L−1 d−1) observed at OLR levels of 72.0 and 96.0 g COD L−1 d−1. Inhibition of the fermentative activity by excess substrate and limitations in the retention capacity of suspended biomass in the reactor still limit the application of higher OLR at the current stage of the technology. Strategies stimulating the cell growth (nitrogen dosing) and biofilm formation (calcium dosing) have potential to expand the operating limit of the CMTR without requiring constructive modifications.

Biodigestion of easily-acidifying cheese whey in a sequential fermentative-methanogenic process: Strategies for boosting energy production and minimizing alkalinization costs

The biodigestion of cheese whey towards enhanced bioenergy production still challenges researchers, considering incipient biohydrogen (bioH2) production during fermentation and the great dependence on an efficient (usually high-cost) alkalinization strategy to achieve high and stable methane production. Using a sequential fermentative-methanogenic process in fixed-film reactors, this study assessed strategies to boost bioH2 production (pH control at ca. 5.5 + prevention of biomass accumulation) and achieve a low-cost stable methanogenic process (replacing NaHCO3 dosing by effluent recirculation and further eliminating any alkalinization approaches). Maintaining fermentation pH values between 5.0 and 5.5 favored bioH2 and butyrate production, but the enhanced establishment of homoacetogenesis (accounting for 70–100 % of the acetate produced) associated with the selective removal of hydrogen-producing bacteria in biomass discharges resulted in a marked unstable hydrogenogenic activity. Processing fermented cheese whey without applying any alkalinization strategy in methanogenesis was further demonstrated to be technically feasible at an OLR of 5.0 kg COD m−3 d−1. COD removal (70–75 %) and the methane yield (150–170 NmL CH4 g−1COD) were equivalent regardless of the alkalinization (NaHCO3 dosing or effluent recirculation) or non-alkalinization approach. However, the alkalinization-derived production cost of methane was reduced from 1.55 USD Nm−3CH4 to zero when fully removing NaHCO3.

Fixed bed in dark fermentative reactors: is it imperative for enhanced biomass retention, biohydrogen evolution and substrate conversion?

Recent studies have revealed gaps related to the bed purpose in fixed-film reactors and its influence on biohydrogen (bioH2) evolution via dark fermentation, given the pivotal role of the basal portion (i.e., feeding chamber) in converting fresh substrate and establishing bioH2 precursor metabolic pathways, which is opposed to that observed in the bed zone. This study aimed to assess the influence of different cell immobilization arrangements (as well as its absence) on biomass retention and washout and their effects on bioH2 evolution and metabolic profiles of an anaerobic tubular reactor (AnTR, which does not include support material), an anaerobic structured-bed reactor (AnSTBR, which includes support material laid out in an orderly pattern) and an anaerobic packed-bed reactor (AnPBR, which considers support material laid out in a disorderly pattern) operated under equivalent operating conditions in the feeding chamber. Higher bioH2 evolution was achieved in the AnSTBR (743.25 mL-H2 L−1 d−1) compared to the AnPBR (662.04 mL-H2 L−1 d−1) and AnTR (586.22 mL-H2 L−1 d−1). For the former, a massive carbohydrate-uptake occurred in the feeding chamber and at the beginning of the bed zone, both comprising an intense metabolic activity versus the upper regions. Conversely, this pattern was restricted to the AnPBR feeding chamber, while an alternative source of lactic activity occurred in the bed zone. Overall, the presence of media in the bed zone proved to be imperative to ensure suitable biomass retention in quanti-qualitative terms in opposition to no-bed, influencing biomass distribution, specific substrate conversion, bioH2 evolution and metabolic pathways.

Feasibility of semi-pilot scale up-flow anaerobic sludge blanket fixed-film reactor for fermentative bio-hydrogen production from palm oil mill effluent

The present study focuses on bio-hydrogen production using palm oil mill effluent (POME) at a semi-pilot scale of an “up-flow anaerobic sludge blanket fixed-film (UASFF) reactor”. The reactor was operated in the palm oil mill industry for over 180 days of operation at ambient temperature through dark fermentation process with different organic loading rates (OLR) of 22–36 g-COD/l.d, depending on the COD concentration of POME. By acclimatizing the sludge, the semi-pilot scale UASFF reactor achieved hydrogen content, and hydrogen production rate (HPR) of 20%–68%, and 12 L H2/d to 39 L H2/d, respectively with a maximum COD removal of 35%. Moreover, from high through pyrosequencing analysis, hydrogen fermentation was attributed to Clostridium sensu stricto, Lactobacillus, and thermoanaerobium spp. This study offers an extensive approach to developing a semi-pilot scale bio-hydrogen production and, provides further prospects for profitable exploitation which could be a promising approach for reaching sustainability and economic feasibility (using wastewater as a low-cost feedstock) in commercial applications for future studies.

Mine Wastewater Treatment with Upflow Anaerobic Fixed Film Reactors

Mine Wastewater Treatment with Upflow Anaerobic Fixed Film Reactors

Optimization of up-flow velocity and feed flow rate in up-flow anaerobic sludge blanket fixed-film reactor on bio-hydrogen production from palm oil mill effluent

The present study aims to optimize key operational parameters of the up-flow anaerobic sludge blanket fixed-film (UASFF) reactor using response surface methodology (RSM). A central composite design (CCD) has been applied to accomplish thirteen experimental runs given two main variables, namely feed flow rate (Qf), and up-flow velocity (Vup). The maximum hydrogen content, hydrogen production rate (HPR), hydrogen yield (HY), and COD removal were achieved at 55%, 4800 mL H2/cycle, 321 mL H2/g-COD, and 24.33%, respectively at Qf 8 L/cycle (HRT = cycle = 10.5 h) and Vup 2.0 m/h. The performance of the parameters from the optimum identified area was assessed at Qf 5.5 L/cycle (HRT = 15.3 h), and Vup 1.8 m/h, resulted in a maximum hydrogen content, HY, and HPR of 72%, 340 mL H2/g-COD, and 5100 mL H2/cycle, respectively. At optimum conditions, Clostridium sensu stricto 1 was found to be the dominant hydrogen-producing bacteria in the system. The results of this study may provide a practical basis for developing a UASFF reactor prototype based on empirical data.

Methanogenic consortia from thermophilic molasses-fed structured-bed reactors: microbial characterization and responses to varying food-to-microorganism ratios

The heterogeneous character of fixed-film reactors may create highly specialized zones with a stratified distribution of microbial groups and varying capabilities to withstand high organic loads in anaerobic digestion (AD) systems. The microbial distribution and methane-producing potential of biomass from different regions (feeding zone and structured bed) of two second-stage thermophilic (55 ºC) fixed-film reactors were assessed. Three levels of food-to-microorganism (F/M) ratio (0.4, 1.0 and 3.0 g-COD g−1VS) using fermented (two-stage AD) and fresh (single-stage AD) sugarcane molasses were tested in batch reactors, simulating low to high organic loads. Specific methane production rates increased as the F/M increased when using fermented molasses, maintaining efficient methanogenesis at substrate availability levels threefold higher than single-stage schemes (3.0 vs. 1.0 g-COD g−1VS). Success in methane production derived from the homogenous establishment (similar in both feeding zone and bed) of syntrophic associations between acetogens (Pelotomaculum, Syntrophothermus, Syntrophomonas and Thermodesulfovibrio), acetate oxidizers (Thermoacetogenium, Mesotoga and Pseudothermotoga) and hydrogenotrophic methogens (Methanothermobacter and Methanoculleus) replacing acetoclastic methanogens (Methanosaeta). Phase separation under thermophilic conditions was demonstrated to boost methane production from sugar-rich substrates, because the process depends on microbial groups (hydrogenotrophs) that grow faster and are less susceptible to low pH values compared to acetotrophs.

Solving the bottlenecks of sugarcane vinasse biodigestion: Impacts of temperature and substrate exchange on sulfate removal during dark fermentation

Removing sulfate prior to methanogenesis and maintaining year-round operation of the plant are the two main bottlenecks to be solved prior to implementing highly efficient bioenergy recovery from sugarcane vinasse via anaerobic digestion. Sulfidogenesis establishment and optimization during vinasse fermentation at two temperature levels (30 °C and 55 °C) were assessed using continuous fixed-film reactors. Simulating the off season through replacing vinasse by molasses was also assessed. Performance results and the distribution of microbial communities were correlated in all operating conditions. Sulfidogenesis was not efficiently established at 30 °C, because sulfate-reducing bacteria (SRB) did not grow favorably during vinasse natural fermentation. Acetate accumulation (∼3 g L−1) resulting from homoacetogenic activity (most likely by Lachnospirales) was observed in this condition. Conversely, sulfate removal (driven by Desulfohalotomaculum and Desulfotomaculum at much lower abundances compared to fermenters, such as Clostridia) was successfully established (84–97 %) under varied hydraulic retention times (18, 12 and 6 h) at 55 °C. Replacing vinasse by molasses negatively impacted SRB due to a sharp drop in pH (<6.0) triggered by lactate accumulation (up to 16.8 g L−1) mainly by Bacillus. However, SRB were resilient to such severe acidic and thermophilic conditions, and sulfate removal was maximized once vinasse was re-introduced. These results strategically represent the best operating strategy for the compositional conditioning of sugarcane vinasse prior to methanogenesis, because the high temperature in which vinasse is released from distillation columns (85–90 °C) facilitates the implementation of thermophilic reactors by eliminating any energy demands related to system heating.

Fate of sloughed biomass in integrated fixed-film systems.

Fate of biofilm sloughing was assessed in a laboratory-scale (LS) integrated fixed-film sequencing batch reactor (IF-SBR) treating synthetic wastewater and in a full-scale (FS) integrated fixed-film activated sludge (IFAS) system treating municipal wastewater. It was observed that the properties of biofilms and flocs, including sludge volume index (SVI), mixed liquor suspended solids (MLSS), effluent suspended solids (ESS), relative hydrophobicity, and composition of extracellular polymeric substance (EPS) were associated with biofilm sloughing and formation of large granular flocs in the LS IF–SBR. In the FS IFAS system, the changes were studied at the molecular level. For example, the extracted EPS content results (the protein to polysaccharide ratio decreased in the flocs and increased in the biofilms, with biofilm sloughing) were complemented with the confocal laser scanning microscopy (CLSM) coupled with molecular specific staining. CLSM analyses revealed that micro-colonies rich in polysaccharides readily sloughed from the carriers. Live-dead staining revealed areas of the biofilm where the viability of biomass was a contributing factor associated with areas of the biofilm susceptible to sloughing. 16S rRNA gene sequencing (Illumina) of FS IFAS samples revealed greater diversity (α-diversity) in biofilms compared to flocs. Biofilm sloughing resulted in a decrease in diversity in biofilms and a corresponding increase in the flocs during sloughing. Microbial population dynamics revealed that bacteria known for denitrification (for example, Comamonadaceae) detached from the biofilms during sloughing, readily associated with the suspended biomass, and were retained in the bioreactors.

Convergent Microbial Community Formation in Replicate Anaerobic Reactors Inoculated from Different Sources and Treating Ersatz Crew Waste.

Future manned space travel will require efficient recycling of nutrients from organic waste back into food production. Microbial systems are a low-energy, efficient means of nutrient recycling, but their use in a life support system requires predictability and reproducibility in community formation and reactor performance. To assess the reproducibility of microbial community formation in fixed-film reactors, we inoculated replicate anaerobic reactors from two methanogenic inocula: a lab-scale fixed-film, plug-flow anaerobic reactor and an acidic transitional fen. Reactors were operated under identical conditions, and we assessed reactor performance and used 16s rDNA amplicon sequencing to determine microbial community formation. Reactor microbial communities were dominated by similar groups, but differences in community membership persisted in reactors inoculated from different sources. Reactor performance overlapped, suggesting a convergence of both reactor communities and organic matter mineralization. The results of this study suggest an optimized microbial community could be preserved and used to start new, or restart failed, anaerobic reactors in a life support system with predictable reactor performance.

A mainstream anammox fixed-film membrane bioreactor with novel sandwich-structured carriers for fast start-up, effective sludge retention and membrane fouling mitigation

Novel sandwich-structured carriers were developed for fast immobilizing anammox sludge, with which a fixed-film membrane bioreactor was further established for treating municipal wastewater. Results showed that fast start-up of the fixed-film reactor with anammox bacteria could be achieved without lag phase, indicated by the respective nitrogen removal efficiency and rate of 70.58 ± 0.66% and 0.12 g N/(L·d). Meanwhile, low membrane fouling 0.0017 bar/hour was also observed. The activity of anammox sludge fixed in the novel carriers gradually stabilized at the level of 6.59 mg N/(g VSS·h), while Candidatus Kuenenia as the dominant anammox bacteria were enriched from the initial abundance of 15.16% to 39.12% after a long-term operation. Consequently, it was demonstrated that the sandwich-structured carriers developed in this study could offer a promising alternative for fast immobilization and start-up of mainstream anammox process.

Analysis of biohydrogen production from palm oil mill effluent using a pilot-scale up-flow anaerobic sludge blanket fixed-film reactor in life cycle perspective

This study aims to analyse the life-cycle assessment of biohydrogen production from palm oil mill effluent (POME) in a pilot-scale up-flow anaerobic sludge blanket fixed-film reactor. The SimaPro LCA software and ReCiPe 2016 impact assessment method were used. Electricity usage was found to be a significant source of environmental impacts, with 50–98% of the total impacts. Furthermore, an improvement analysis was conducted, resulted in a reduction in all impacts, especially global warming impact with 77% reduction from 818 to 189 kg CO2-eq per kg biohydrogen. While shifting the pilot reactor to Sarawak may further lessen the impact to 142 kg CO2-eq due to cleaner grid in that region. Besides, if the environmental burden avoided due to usage of POME is considered, the global warming impact can be further reduced to 54.9 kg CO2-eq. Thus, the pilot reactor has huge potential, especially in utilizing waste to produce bioenergy.

Treatment of Hospital wastewater with submerged aerobic fixed film reactor coupled with tube-settler

In this study, Hospital wastewater was treated using a submerged aerobic fixed film (SAFF) reactor coupled with tubesettler in series. SAFF consisted of a column with an up-flow biofilter. The biological oxygen demand (BOD)5, chemical oxygen demand (COD), nitrate and phosphate were the chosen pollutants for evaluation. The pollutants removal efficiency was determined at varying organic loading rates and hydraulic retention time. The organic loading rate was varied between 0.25 and 1.25 kg COD m−3 d−1. The removal efficiency of SAFF and tubesettler combined was 75 % COD, 67 % BOD and 67 % phosphate, respectively. However, nitrate saw an increase in concentration by 25 %. SAFF contribution in the removal of COD, BOD5 and Phosphate was 48 %, 46 % and 29 %, respectively. While for accumulation of nitrate, it was responsible for 56%, respectively. Tubesettler performed better than SAFF with 52 %, 54 % and 69 % reduction of COD, BOD5 and phosphate, respectively. But in terms of nitrate, tubesettler was responsible for 44 % accumulation. The nutrient reduction decreased with an increase in the organic loading rate. Nitrification was observed in the SAFF and tubesettler, which indicated a well-aerated system. An anaerobic unit is required for completing the denitrification process and removing nitrogen from the effluent. The better performance of tubesettler over SAFF calls for necessitates extended retention time over design criteria. Further studies are beneficial to investigate the impact of pharmaceutical compounds on the efficiency of SAFF.