Fixed Bed Biofilm Reactor Research Articles

Evaluation of a pilot-scale anaerobic biofilm reactor for the treatment of slaughterhouse effluents in rural areas

ABSTRACT Rural slaughterhouses often lack strict effluent treatment rules, resulting in inadequate treatment prior to release into water bodies. Slaughterhouse wastewater (SWW) is a high-strength effluent, posing risks of contamination to ecosystems and human health. To tackle the need for suitable technologies in these areas, this study evaluated a 215 L pilot-scale fixed-bed biofilm reactor (FBBR), known for its simplicity in implementation, operation, and maintenance. During the operation, an initial startup period, with the liquid fraction of fruit and vegetable waste (LF-FVW) was conducted, followed by a gradual transition to SWW, creating a co-digestion period during the substrate transition. Organic load variations (1.59, 3.35, and 4.00 kgCOD/m3·d), corresponding to flow rates of 50, 75, and 120 L/d, respectively, were implemented to address potential alterations in effluent concentration and composition in authentic rural settings. Removal rates of up to 83.69, 91.81, 87.00, and 92.00% were achieved for COD, sCOD, TS, and VS, respectively, with an average removal of 32.00% for TN, and biogas production exceeded 300 L/h at 4.00 kgCOD/m3·d. These results suggest that FBBR implementation in rural areas effectively confronts SWW treatment challenges by reducing contamination, generating biogas, and adapting to rural conditions.

Performance evaluation of species varied fixed bed biofilm reactor for wastewater treatment of Dhobi Khola outfall, Setopul, Kathmandu, Nepal

The sustainability of wastewater treatment plants poses significant challenges for developing countries, necessitating substantial investment for operation and maintenance. Biofilm reactors seeded with specific species of microorganisms were investigated under controlled environmental conditions. However, the performance evaluation of such reactors under natural conditions remains largely underexplored. This study investigated wastewater treatment capabilities of bench-scale fixed bed biofilm reactors, employing various species (Wastewater Microbes, Pseudomonas, Algae, and a co-culture of Algae and Pseudomonas). The reactors (Treatments and Control) were filled with 28 mm nominal-size local aggregates as packing media, operated under different contact times, and subjected to varying concentrations of heavy metals (Zn, Cd). To assess the reactor performances, the Bland-Altman Plot and Chemical Oxygen Demand (COD) removal kinetics were evaluated.The results revealed that the reactor initiated with a co-culture exhibited the optimal COD removal efficiency, reaching 84 ± 1 %. The reactor initially seeded with wastewater microbes exhibited the highest heavy metal elimination, achieving 94 ± 1 % and 88 ± 1 % removal for Zn and Cd respectively. The wastewater-seeded reactor demonstrated the zero-order COD removal kinetic coefficient (k) of 46.41 mg/L/h at an average influent COD concentration of 558 mg/L at 10 h contact time. While Pseudomonas-seeded reactor demonstrated k = 0.73 mg/L/h at 20 h contact time with 69 mg/L influent COD and heavy metal concentrations Zn = 26 mg/L and Cd = 3.57 mg/L.The findings of this study suggest that variations in environmental conditions, contact time, and heavy metal concentration have minimal impact on the pollutant removal efficacy of the reactors, and provide robust evidence for their viability as a sustainable alternative in municipal wastewater treatment. The study also identifies the possibility of treating specific wastewater characteristics by altering the dominant species in the reactors, paving the way for further research on the efficacy of other microbial genomes in fixed bed biofilm reactors.

Operational characteristics in varied gradients of low carbon-to-nitrogen ratios utilizing a novel integrated bacteria-algae synergistic biofilm reactor for wastewater treatment

Evaluating a novel algal-bacterial biofilm integrated reactor (A-BBR) designed to reduce energy consumption and greenhouse gas emissions, wastewater treatment characteristics were simulated at low carbon-to‑nitrogen ratios. Pollutant removals were investigated under low organic loads at different carbon-to‑nitrogen ratios (ranging from 7.24 to 4.59). COD and NH4+-N removal rates surpassed 90 %, with TN removal exceeding 80 %, demonstrating a notable performance improvement over the fixed-bed biofilm reactor (FBBR). The efficient utilization of organic substrate during denitrification by the bacteria-algae symbiosis system resulted in an increase in nitrogen removal per unit concentration of organic matter. Tracking studies of photosynthetic oxygen production rate versus specific aerobic rate and chlorophyll in the reactor demonstrated that additional aeration was unnecessary during the photoreaction phase, reducing energy losses. The decrease in the carbon-to‑nitrogen ratio was positively correlated with the increase in facultative diatom species within the biofilm. As the carbon-to‑nitrogen ratio had decreased from 7.24 to 4.59, the content of diatoms had increased by over tenfold compared to the initial stage. Furthermore, as the diversity of algae species increased, the difference between the photosynthetic oxygen production rate and the specific aerobic rate had risen from 7.6 to 13.8. This indicated that the algal-bacterial biofilm system with a richer diversity of algae exhibited a higher photosynthetic oxygen production rate compared to the monoalgal system. These results furnish valuable insights for future inquiries into the utilization and underlying mechanisms of bacterial and algal biofilms in the context of water treatment.

Deciphering responses of sulfur autotrophic denitrification system to the single and joint stress of Zn(II) and dialkyldimethyl ammonium compounds: Performance, microbial community and different fractions of resistance genes

Zn(II) and dialkyldimethyl ammonium compounds (DADMAC) are common heavy metal and disinfectant contaminants in wastewater treatment plants. The response of sulfur autotrophic denitrification (SAD) system under single and joint stress with different concentrations of Zn(II) (1–25 mg/L) and DADMAC (0.2–10 mg/L) was evaluated using sequencing batch fixed-bed biofilm reactors in this study. The joint stress of high concentrations of Zn(II) and DADMAC had stronger inhibitory effects on microbial activity and metabolic function genes compared to the single stress, thus significantly inhibiting the performance of the SAD system. Furthermore, Zn(II) stress contributed to the proliferation of resistance genes (RGs) in water (w-RGs), whereas stress of DADMAC was able to induce the proliferation of intracellular RGs (si-RGs) and extracellular RGs (se-RGs) in sludge. And under the joint stress of Zn(II) and DADAMC, the abundances of si/se-RGs were much higher than that under single stress, with a higher risk of RGs transmission. The α-Helix/(β-sheet + random coil) in tightly bound extracellular polymeric substances correlated positively with si-tnpA-04 and se-tnpA-04. Horizontal gene transfer via mobile genetic elements was the main mode of RGs transmission. This work assessed the risk of DADAMC and Zn(II) in the SAD system and established new insights into the transmission of three-fraction RGs under DADMAC and Zn(II) stress.

The effects of ammonium loading rates and salinity on ammonium treatment of wastewater from super-intensive shrimp farming

Treatment of wastewater from super-intensive shrimp farming (SISF) for discharge or recirculation purposes is currently attracting the attention of managers and researchers. The fixed bed biofilm reactor (FBBR) has been successfully used for biological treatment of drinking water as well as for wastewater treatment in aquaculture farm. Ammonium and salinity are important factors affecting the efficiency of pollutants treatment. This paper presents the results of research on ammonium treatment in super-intensive shrimp wastewater by aerobic microbiological process using FBBRs. The results showed that at ammonium loading rates of 0.014; 0.028; 0.049 and 0.070 kg/m3/d, at salinity of 10‰, the ammonium removal efficiencies were 98 - 99; 97.7 - 98.8; 96.8 – 98.7 and 95.7 – 98.0 percent respectively (ammonium concentrations in effluent were 0.05 – 0.1; 0.12 – 0.23; 0.23 – 0.56 and 0.51 – 1.07 mgN/l, respectively), at salinity of 15‰, the ammonium removal efficiencies were 95.8-96.0, 94.5-92.0, 93.1-92.3 and 66.8-68.8 percent respectively (ammonium in effluent were 0.20 – 0.21; 0.55 – 0.8; 1.20 – 1.35 and 7.8 – 8.3 mgN/l, respectively), at salinity of 20‰, the ammonium removal efficiencies were 92.0-96.0, 87.0-89.0, 69.1-70.9 and 59.6-66.0 percent respectively (ammonium in effluent were 0.2 – 0.4; 1.1 – 1.3; 5.1 – 5.4 and 8.5 – 10.1 mgN/l, respectively). This result showed that the influence of ammonium loading and salinity on ammonium treatment efficiency was very significant.

Mathematical modelling and comparative analysis of treatment technologies for upgrading wastewater treatment plants: A case study of biofilm reactors in El-Gouna, Egypt

In recent years, Moving Bed Biofilm Reactors (MBBRs) have been preferred to conventional processes with suspended biomass. The main reason for this preference is that it can achieve better removal efficiencies than conventional systems with smaller footprints. However, unlocking the full potential of MBBRs in large-scale WWTPs remains challenging in real life. In this study, the performance of three different treatment technologies, Extended Aeration Activated Sludge (EAAS), Hybrid Fixed Bed Biofilm Reactor (HFBBR), and Hybrid Moving Bed Biofilm Reactor (HMBBR), was investigated over a year in a WWTP located in El-Gouna, Egypt. The COD removal efficiencies of the three systems were comparable, with the EAAS achieving 93.5%, HFBBR 94%, and HMBRR 95%. Nevertheless, the NH4 removal efficiency of the EAAS was slightly lower (97.5%) than that of the HFBBR and the HMBBR, that achieved a removal efficiency of 98%. BioWin Software was able to mimic the real case of the WWTP of El-Gouna and critically defined all plant limitations and operational data. Different simulations were modeled to test the hydraulic and organic loading capacities of the three systems under different scenarios and operating conditions. The HMBBR system failed to withstand the increase in organic load because of the biomass sloughing effect and subsequently high TSS loads in the settlers. Biomass sloughing overloaded the settlers and lead to biomass loss in the effluent. As the settleability of the HMBBR sludge was significantly lower than for the HFBBR the TSS loss in the effluent happened that much earlier that the moving carrier application had an adverse effect contradicting with the primary purpose of adding media carriers. Model simulations and data analysis findings were used to recommend the most suitable configuration for upgrading an existing system using the attached growth technique with all kinetic parameters and operational conditions. The recommended configuration focuses mainly on the separation of plastic media in a compartment with a very low hydraulic retention time to absorb the incoming shock load.

Assessment of hybrid fixed and moving bed biofilm applications for wastewater treatment capacity increase – In situ tests in El-Gouna WWTP, Egypt

This paper provides a procedure for comparing the performance of different biofilm carrier medias and their surrounding suspended biomass through oxygen uptake rate (OUR) tests. For in situ (oxygen uptake rate (OUR) measurements, three identical lab scale biofilm reactors were set up at the El Gouna wastewater treatment plant (WWTP). In this setup, two options of media for moving-bed biofilm reactors (MBBR) and one media for fixed-bed biofilm reactors (FBBR) were compared. The WWTP also used the same carrier in a real scale hybrid application to analyze how the interactions between the carrier type and the suspended biomass influences the overall performance. The in situ OUR approach is recommended to measure the contribution of the biofilm fixed biomass under site specific conditions. Specifically, settleability and diffusion limitations are the two opposite poles that cannot be predicted adequately for mild climate conditions based on the literature. A biofilm carrier application can add but actually can also reduce the capacity in a hybrid activated sludge system: The added MBBR-media was able to grind down the sludge flocs forming a poorly settleable suspended biomass. The added FBBR-media can lead to extracellular polymeric substances (EPS) rich biofilms that contribute very little as substrate and oxygen are unavailable for the microorganisms present in the biofilm. In this application of the comparison procedure, Kaldnes K1 like MBBR media was compared with a recycling MBBR carrier option (poly propylene bottle caps) and Jäger Envirotech “BioCurlz™” FBBR media. The study showed higher average rates for the MBBR but decreased settleability. The FBBR showed higher peak rates when flushed to break up the biofilm and well settleable sludge. The determination of OUR per g of volatile solids (SOUR) showed comparable results for all the carriers and in warm conditions, only the capacity to accommodate biomass determines the contribution of the carrier.

Acclimatizing waste activated sludge in a thermophilic anaerobic fixed-bed biofilm reactor to maximize biogas production for food waste treatment at high organic loading rates

Thermophilic anaerobic digestion (TAD) provides a promising solution for sustainable high-strength waste treatment due to its enhanced methane-rich biogas recovery. However, high organic loading rates (OLR) exceeding 3.0 kgCOD/m3/day and short hydraulic retention times (HRT) below 10 days pose challenges in waste-to-energy conversion during TAD, stemming from volatile fatty acids (VFAs) accumulation and methanogenesis failure. In this study, we implemented a stepwise strategy for acclimatizing waste activated sludge (WAS) in a thermophilic anaerobic fixed-bed biofilm reactor (TA-FBBR) to optimize methanogen populations, thereby enhancing waste-to-energy efficiencies under elevated OLRs in food waste treatment. Results showed that following stepwise acclimatization, the TA-FBBR achieved stable methane production of approximately 5.8 L/L-reactor/day at an ultrahigh OLR of ∼20 kgCOD/m3/day and ∼15 kgVS/m3/day at 6-day HRT in food waste treatment. The average methane yield reached 0.45 m3/kgCODremoval, attaining the theoretical production in TAD. Moreover, VFA concentrations were stabilized below 1000 mg/L at the ultrahigh OLR under 6-day HRT, while maintaining an acetate/propionate ratio of > 1.8 and a VFA/TAK ratio of < 0.3 serving as effective indicators of system stability and methane yield potential. The microbial community analysis revealed that the WAS acclimatization strategy fostered the microbial diversity and abundance of Methanothermobacter and Methanosarcina. Methanosarcina in the biofilm were observed to be twice as abundant as Methanothermobacter, indicating a potential preference for biofilm existence among methanogens. The findings demonstrated an effective strategy, specifically the stepwise acclimatization of WAS in a thermophilic fixed-bed biofilm reactor, to enhance the food waste treatment performance at high OLRs, contributing valuable mechanistic and technical insights for future sustainable high-strength waste management.

Biological treatment methods of ship sewage: Case study

The study aims to compare three sewage biological treatment methods- activated sludge, moving bed biofilm reactor (MBBR), and fixed bed biofilm reactor. The activated sludge method is the most used in ship sewage treatment. However, biofilm carrier methods, such as MBBR and fixed bed reactors, have improved in their effectiveness with industrial wastewater, with ship sewage being considered industrial. An experiment was carried out with ship untreated sewage samples, and chemical oxygen demand (COD) concentrations from different methods were analyzed and compared.

Effects of Different Polymeric Materials on the Bacterial Attachment and Biofilm Formation in Anoxic Fixed-Bed Biofilm Reactors

Six biofilm carriers with different polymer were studied in fixed-film systems under anoxic conditions. Different media of polymers influence wastewater treatment performance. The aim of this study was to investigate different polymeric materials, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polypropylene (PP), high-density polyethylene (HDPE), and polymethyl methacrylate (acrylic), that affect bacterial attachment and biofilm formation in biofilm-based wastewater treatment technologies. Water contact angle (WCA) measurement was employed to analyze the role of wetting (hydrophilic/hydrophobic) of polymeric material surfaces in the initial phase of bacterial attachment. The increase of biofilm formation during the observation was determined by gravimetric (total attached solid) and microscopic (SEM and CLSM) analysis. The results showed the value for WCA of PET < HDPE < PVC < PP < acrylic, which indicated that a higher hydrophilicity surface leads to a higher total attached solid (TAS), biofilm formation rate, and biofilm thickness on the surface of media. The hydrophilic material (i.e., PET and HDPE) demonstrated wastewater treatment performance better than slightly hydrophilic material (i.e., PVC, PP, and acrylic) under a steady-state period (over an 80-day operation). The data showed a positive correlation between hydrophilic material and COD, NH4+-N, and TP removal. Hydrophilic material was beneficial for a fast start-up and stable biofilm formation of a fixed-bed biofilm reactor. PET media showed feasible polymer types compared to HDPE, PVC, and PP; thus, it can be used as an alternative biofilm carrier media in a larger-scale application. The findings of this study highlighted the polymeric material type has a significant effect on the performance of fixed-bed wastewater treatment.

Development and characterizations of hydrogenotrophic denitrification granular process: Nitrogen removal capacity and adaptability

Hydrogenotrophic denitrification (HD) is a promising autotrophic biological process for advanced nitrogen removal, while sludge granulation was seldom reported. This study aimed to cultivate granular sludge to improve capacity and stability of HD process. The resulting HD granular sludge performed high nitrogen removal rate (NRR) of 0.42 ± 0.0.4 kgN/(m3·d) with low accumulation of nitrite and nitrous oxide emission. HD granular sludge reactor performed over 3 times higher NRR compared to that in HD fixed-bed biofilm reactor (0.13 ± 0.01 kgN/(m3·d). Besides, granular sludge reactor could treat groundwater well even at the low temperature of 15 °C. The dominant genera were Hydrogenophaga and Comamonas in granular sludge, and Dechloromonas in biofilm. Noticeably, sulfate in the groundwater stimulated the growth of sulfur converting microbes with increasing abundances of sulfite reductase gene and sulfate-reducing bacteria Desulfovibrio. This study highlights the potential implementation of HD process in granular sludge reactor for advance nitrogen removal from impaired groundwater.

Two-phase (acidogenic-methanogenic) anaerobic fixed bed biofilm reactor enhances the biological domestic sewage treatment: Perspectives for recovering bioenergy and value-added by-products.

The organic matter bioconversion into methane during anaerobic digestion (AD) comprises different steps, the acidogenic and methanogenic phases being clearly distinct in terms of metabolic activities. In this work, new configurations of anaerobic fixed bed biofilm reactors (AFBBR) were operated under conventional methanogenic conditions (single phase - SP-AFBBR, M1R), and in a sequential two-phase system, acidogenic reactor followed by methanogenic reactor (TP-AFBBR, AcR+M2R), in order to verify the impact of the AD phase separation on the overall system performance in operational, kinetics and microbiological aspects. The results indicated that feeding the methanogenic reactor with the acidogenic effluent stream provided a shorter operating start-up period (11 and 32 days for SP and TP-AFBBR, respectively), a greater alkalinity generation (0.14 and 0.41g-CaCO3·g-CODremoved-1 for M1R and M2R, respectively), and the optimization of biomethane production (methane yield of 95 and 154N-mLCH4·g-CODremoved-1 for M1R and M2R, respectively). The COD removal kinetics was also favored in the TP-AFBBR (k1-COD=1.4 and 2.9 h-1 for M1R and M2R, respectively), since the soluble fermentation products were readily bioavailable to the biomass in the reactor. Hydrogenotrophic methanogenesis was the predominant pathway in the M2R, while the Methanosaeta-driven acetoclastic pathway predominated in the M1R. The greater diversity of Bacteria and Archaea in M2R denotes a better balance between the species that degrade volatile organic acids from AcR (i.e. Syntrophorhabdus, Syntrophus and Syntrophobacter) and the hydrogenotrophic methanogens (Methanoregula, Methanolinea and Methanospirillum) that consume the biodegradation products. The estimated bioenergy generation potential (range of 0.39-0.64kWh·m-3-sewage considering the COD removed) for full-scale TP-sewage treatment plants evidences the feasibility of energetic recovery in the domestic sewage anaerobic treatment.

Integrated adsorption and biological removal of the emerging contaminants ibuprofen, naproxen, atrazine, diazinon, and carbaryl in a horizontal tubular bioreactor

Groundwater and surface water bodies may have contaminants from urban, industrial, or agricultural wastewater, including emerging contaminants (ECs) or micropollutants (MPs). Frequently, they are not efficiently removed by microbial action due to their minimal concentration in water and the low microbiota affinity for complex compounds. This work developed a process allowing the adsorption of contaminants and their simultaneous biodegradation using horizontal tubular fixed-bed biofilm reactors (HTR). Each HTR has two zones: an equalizer-aerator of the incoming liquid flow and a fixed bed zone. This zone was packed with a mixed support material consisting of granular bio-activated carbon (Bio-GAC) and porous material that increases the bed permeability, thus decreasing the pressure drop. Five microbial communities were acclimated and immobilized in granular activated carbon (GAC) to obtain different specialized Bio-GAC particles able to remove the micropollutants ibuprofen, naproxen, atrazine, carbaryl, and diazinon. The Bio-GAC particles were transferred to HTRs continuously run in microaerophilia at several MPs loading rates. Under these conditions, the removal efficiencies of MPs, except atrazine and carbaryl, were around 100.

Experimental investigation of biofilm carriers of varying shapes, sizes, and materials for wastewater treatment in fixed bed biofilm reactor: a qualitative study of biocarrier performance

AbstractBACKGROUNDBiofilm carriers were introduced in the early 1990s mainly to abate chemical oxygen demand (COD). However, studies have continued investigating few biocarriers repeatedly, without studying a large number of carriers in a single study under similar conditions.RESULTSThe current study investigated the performance of nine synthetic and eight natural biofilm carriers for 7 days of palm oil mill effluent (POME) treatment in terms of COD removal. A fixed bed biofilm reactor (FBBR) was 100% packed with biocarriers and operated at 35 °C. Performance based on the 7th day COD removal could be ranked in the following order: green ammonia absorption stone (91%), K1 micro (88%), coral sand (87.8%), volcanic stone (86.6%), Micro Media (85.5%), 1.6 cm BioBall (85%), pebble (82.4%), porous ceramic ring (82.3), K1 (82.1%), non‐porous ceramic ring (80.9%), brown ammonia absorption stone (78.6%), biological filter (77.7%), Ultra Media (76.8%), blue media (69.3%), 3.0 cm BioBall (68.8%), 2.5 cm BioBall (66.5%), and loofah sponge (63%).CONCLUSIONThe smallest carrier, K1 micro, yielded the highest COD removal (88%) on day 7 among the other synthetic carriers, while green ammonia absorption stones provided the highest quality effluent from day 1 (3565 mg COD L−1) to day 7 (780 mg COD L−1) and delivered the shortest start‐up compared with all natural and synthetic carriers. The discussion revealed that all carrier functionalities (i.e., scale, shape, surface pores, roughness, material, surface area, porosity, and durability) play a key role in deciding carrier quality. The current study also introduced ‘carrier efficiency limit’, which refers to the carrier's capacity to entrap biomass and immobilize microorganisms. © 2022 Society of Chemical Industry (SCI).

Decolorization of Textile Dyes in a Fixed‐Bed Biofilm Reactor

AbstractA fixed‐bed biofilm reactor (FBBR) was developed and its performance in decolorizing synthetic dye mixtures and textile industry effluents was evaluated in both batch and continuous modes. It was observed that yeast extract was important as the carbon source in the FBBR feed for color removal. However, the requirement for yeast extract in FBBR is very small compared to that in suspended cell cultures. Structural changes in dyes due to biological treatment were assessed from ultraviolet‐visible spectral and high‐performance liquid chromatography (HPLC) analyses. Gas chromatography‐mass spectrophotometry (GC‐MS) investigations confirmed that the metabolites formed were nontoxic and benign.

Decolourization of textile dyes and textile industry effluent in a fixed bed biofilm reactor using native microorganisms

Textile and apparel industry plays a huge role in the Sri Lankan industrial sector, accounting more than 40% of export earnings in the country. Textile wet processing produces large volumes of coloured effluents which have potential to cause negative impacts on environment and various adverse health effects if not properly treated.

Achieving rapid mainstream deammonification through inoculating long-term refrigerated sidestream sludge in plug-flow fixed-bed biofilm reactor

The start-up of a stable mainstream deammonification requires sufficient anaerobic ammonia-oxidizing bacteria (AnAOB). This study used a plug-flow fixed-bed reactor (PFBR) to verify the feasibility of establishing the mainstream deammonification system by inoculating the sidestream sludge after long-term refrigeration. A rapid resuscitation of the mainstream deammonification system was accomplished by controlling the front-end aeration rate of the PFBR. Results showed that the system was rapidly resuscitated in 44 days eventually with the nitrogen removal rate and nitrogen removal efficiency of 0.1 kg N·(m3·d)−1 and 79.1%, respectively. Also, the efficient performance was secured by the proportionate approaching equilibrium of AnAOB and ammonia-oxidizing bacteria (AOB) activity of 2.35 ± 0.40 and 2.60 ± 0.29 mg N·(g VSS·h)−1, respectively. In addition, Pearson correlation analysis revealed that AnAOB abundance (detected Candidatus Kuenenia) negatively correlated with the AOB (mainly Nitrosomonas)/AnAOB abundance ratio, while correlated positively with the residual ammonium concentration of a region. Furthermore, long-term refrigeration probably reduced the cross-feed relationship between AnAOB and other symbiotic organisms (Armatimonadetes and Chloroflexi) to maintain the basic metabolism. Meanwhile, extracellular polymeric substances produced by other genera (order Xanthomonadales and Pseudomonadales) decreased the mass transfer, protecting AnAOB from unfavorable conditions, thereby facilitating high AnAOB abundance during refrigeration. Thus, this study provides a promising perspective towards the practical applications of mainstream process.

Application of an indigenous microorganisms-based fixed-bed GAC-biofilm reactor for passive and sustainable treatment of oil sands process water through combined adsorption and biodegradation processes

In this study, a fixed-bed biofilm reactor (biofilter) was developed and applied for oil sands process water (OSPW) remediation by using granular activated carbon (GAC) as packing media. Using quantitative polymerase chain reaction (qPCR) detection, the total bacterial copy number (16S) in the GAC biofiltration system was found to reach a relatively stable level (1.3 ± 0.2 × 109 copies/g GAC) after 62 days of operation, and the thickness of biofilm on GAC surface was 26.7 ± 4.3 μm based on the scan of confocal laser scanning microscopy (CLSM). The established GAC-biofilter showed 95.4% naphthenic acids (NAs) removal from raw OSPW after 2 months of operation. The GAC-biofilter also showed 88.3% NAs removal after a long operation time (2 years), indicating its sustainable bioremediation capacity for OSPW. 16S and 18S rRNA gene-targeted metagenomic sequencing showed that the microbial community in the GAC biofilter had higher diversity and richness than that found in the sand biofilter which was used for OSPW treatment previously. Comamonadaceae and Saccharomycotina were found to be the dominant bacterial and fungal families in the GAC biofilter, respectively. Xenobiotic metabolism function of the microbial community may contribute significantly to the biodegradation of NAs. The GAC biofiltration process is a promising passive OSPW treatment approach that can be used in-situ.

Ecotoxicity and Antimicrobial Inhibition Assessment of Effluent from an Anaerobic Bioreactor Applied to the Removal of Sulfamethoxazole and Ciprofloxacin Antibiotics from Domestic Sewage

This study evaluated the ecotoxicity effects of effluent from an anaerobic fixed bed biofilm reactor (AFBBR) removing the sulfamethoxazole (SMX - 403 ± 104 ng L−1) and ciprofloxacin (CIP - 294 ± 123 ng L−1) antibiotics from domestic sewage in some microorganisms (Brevundimonas sp., Escherichia coli, Ochrobactrum sp., Sphingomonas sp.) and benthic organisms (Allonais inaequalis and Chironomus sancticaroli). The AFBBR showed high removal efficiency of SMX (85 ± 10%) and CIP (81 ± 16%) and completely eliminated the acute ecotoxicological effect on the C. sancticaroli insect larvae. The bioreactor effluent did not cause any inhibition on the cell growth of the microorganisms. Nonetheless, the A. inaequalis was extremely sensitive to the reactor effluent (100% mortality), probably due to the death of bacteria and algae essential to the nutrition of the Oligochaeta. Regarding the adult insect emergency of C. sancticaroli, a reduction of 50% was observed after 17 days of exposure to the effluent with 40 μgSMX L−1, inhibiting the larval development, which did not occur for CIP. The antimicrobial inhibition by CIP present in the domestic sewage resulted in EC50 (median effective concentration) values of 2.5, 0.9, 3.1 and 0.1 mgCIP L−1 for Ochrobactrum sp., Brevundimonas sp., Sphingomonas sp. and E. coli, respectively. Assessing the effect of antibiotics in the effluent on the microorganisms’ growth by a disk diffusion test, only E. coli culture showed inhibition at the concentration of 5.0 mgCIP L−1. The study emphasized the potential of AFBBR to reduce ecotoxicity in the sewage on aquatic biota.

Carbon Source Competition in Biological Selenate Reduction under Other Oxyanions Contamination

Selenate removal in drinking water is being vigorously debated due to the various health issues concerned. As a viable treatment option, this study investigated a fixed-bed biofilm reactor (FBBR) with internal recycling. The experimental design tested how hydraulic loading rate and electron donor affect selenate reduction together with other oxyanions. The tested accompanying oxyanions were nitrate and perchlorate and experiments were designed to test how an FBBR responded to the limited electron donor condition. The results showed that the reactor achieved almost complete selenate reduction with the initial hydraulic loading rate of 12 m3/m2/day (influent concentration of 1416 µg SeO42−/L). Increasing the hydraulic loading rates to 16.24 and 48 m3/m2/day led to a gradual decline in selenate removal efficiency. A sufficient external carbon source (C:N of 3.3:1) achieved an almost complete reduction of nitrate as well as selenate. The FBBR acclimated to selenate instantaneously and reduced nitrate via synergistic denitrification. An experiment with another oxyanion addition, perchlorate (459 µg ClO4−/L), revealed that perchlorate-reducing bacteria were more strongly associated with carbon limitation than selenate-reducing bacteria, which can help us to understand parallel reactions in FBBRs. This research provides a framework to further study the use of electron donor-controlled FBBRs for simultaneous reduction of selenate and other oxyanions threatening the drinking water-related environment and public health.