Fixed-bed Bioreactor Research Articles

Implementation of an Upflow Fixed Bed Bioreactor for Denitrification Coupled to Methane Oxidation: Performance and Biomass Development Under Anoxic Conditions

Denitrification coupled to methane oxidation (DOM) has been shown to be an appropriate process for wastewater treatment applications, since it can reduce greenhouse gas emissions and nitrogen discharges, making wastewater treatment plants more environmentally sustainable. Study of DOM has focused on laboratory-scale application using membrane biological reactors (MBR) or sequency batch reactors (SBR), which have been shown to be able to retain DOM biomass and therefore appropriate for use with this process. However, it is necessary to expand knowledge of the behavior of this process using other configurations, with a view to scaling up. Therefore, in this study, an upflow fixed bed bioreactor (UFBR) was implemented using plastic carriers such as bioballs and Biochips® to carry out the DOM process under anoxic conditions. The reactor reached stable nitrogen removal conditions after approximately 400 days of continuous operation, forming a biomass composed of denitrifying methane-oxidizing microorganisms where the genus Anaerolinea and Methylocystis predominated. Once the biomass was formed and the DOM process was stabilized, maximum nitrite and nitrate removal rates of 17.6 mgN-NO2−/L-d and 8.9 mgN-NO3−/L-d, respectively, and a removal efficiency of methane up to 77% were obtained. This demonstrates the feasibility of the application of the DOM process under anoxic conditions using fixed bed bioreactors, which is promising for further nitrogen removal from wastewater using a varied reactor configuration easily to scaled-up.

Continuous Fixed Bed Bioreactor for the Degradation of Textile Dyes: Phytotoxicity Assessment

This study explores a novel bioremediation approach using a continuous upflow fixed bed bioreactor with date pedicels as a biosupport material. Date pedicels offer a dual advantage: providing microbial support and potentially acting as a biostimulant due to their inherent nutrients. This research is divided into two phases: with and without microbial introduction. The bioreactor’s efficiency in removing two common textile dyes, RB19 and DR227, was evaluated under various conditions: fixed bed high, the effect of the initial concentration of the pollutant, and recycling the RB19 solution within the bioreactor. Optimization studies revealed an 83% removal yield of RB19 dye with an initial pollutant concentration of 100 mg·L−1 using activated sludge as inoculum. The bioreactor developed its own bacterial consortium without initial inoculation. Microscopic analysis confirmed the presence of a diverse microbial community, including protozoa (Aspidisca and Paramecium), nematodes, and diatoms. The bioreactor exhibited efficient removal of RB19 across a range of initial concentrations (20–100 mg/L) with similar removal efficiencies (around 65%). Interestingly, the removal efficiency for DR227 was concentration-dependent. The bioreactor demonstrated the ability to enhance the biodegradability of treated RB19 solutions. Phytotoxicity tests using watercress and lettuce seeds revealed no negative impacts on plant growth. SEM and FTIR analyses were conducted to examine the biosupport material before and after biotreatment.

Selenium and concomitant anions removal in a fixed bed bioreactor to satisfy drinking water regulations and subsequent stability check of selenium-laden biosludge

This is the first successful report on selenium bio-attenuation to satisfy drinking water regulations as per Indian Standards (10 μg/L) in the presence of concomitant nitrate and sulfate from water sources utilizing a fixed bed bioreactor. The bioreactor was immunized with blended microbial culture and worked in downflow mode under anoxic conditions at 30 ± 2 °C for around 190 days under varying influent selenate (100–500 μg/L as selenium), nitrate (50 mg/L), sulfate concentrations (as per selenium removal) and necessary dose of acetic acid (as COD, a carbon source) in synthetic groundwater, operated at an empty bed contact time (EBCT) of 45–120 min. After supplying an adequate dosage of sulfate and alteration of EBCT, selenium was found to comply with drinking water regulations and nitrate was completely removed. X-ray diffraction and transmission electron microscopy analyses depicted nanocrystalline selenium sulfides (SeS and SeS2) formation as the possible mechanisms of selenium removal. Extended toxicity characteristic leaching procedure (TCLP) extractions confirmed a maximum selenium leaching of 52 and 282 μg/L during anoxic and oxic extractions, respectively. Long-term column leaching (>3-month equilibration) under aerobic conditions at pH 7 confirmed the produced precipitate to be essentially stable (∼0.14% Se leaching). This work exhibits the synchronous bioremoval of selenium and its co-anions from contaminated water complying with drinking water standards, and leaving a stable and non-hazardous selenium-laden biosludge.

Treatment of pulp and paper mill effluent through combined aerobic and anaerobic suspended fixed-bed bioreactor.

This study explored using ultrafiltration (UF) membranes to treat pulp and paper mill wastewater, implementing a novel Taguchi experimental design to optimize operating conditions for pollutant removal and minimal membrane fouling. Researchers examined four factors: pH, temperature, transmembrane pressure, and volume reduction factor (VRF), each at three levels. Optimal conditions (pH10, 25°C, 6bar, VRF 3) led to a 35% reduction in flux due to fouling and high pollutant rejections: total hardness (83%), sulfate (97%), spectral absorption coefficient (SAC254) (95%), and chemical oxygen demand (COD) (89%). Conductivity had a lower rejection rate of 50%. Advanced imaging techniques like atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed reduced membrane fouling under these conditions. The Taguchi method effectively identified optimal conditions, significantly improving wastewater treatment efficiency and promoting environmental sustainability in the pulp and paper industry. PRACTITIONER POINTS: This study optimized UF membrane conditions for pulp and paper mill wastewater, reducing fouling and enhancing pollutant removal, offering practical strategies for industrial treatment. AFM and SEM provided key insights into membrane fouling and mitigation, promoting real-time diagnosis and optimization for enhanced treatment efficiency. Prioritizing anaerobic fixed-bed systems in wastewater treatment is beneficial for achieving high COD removal efficiency. Optimizing hydraulic retention time (HRT) in these systems can further improve their overall effectiveness and sustainability.

The stratified response of heterotrophic, autotrophic or mixotrophic denitrification to enrofloxacin stress along different filling heights in up-flow fixed-bed bioreactors

Antibiotics frequently exist in nitrate wastewater and seriously threaten biological denitrification. This study investigated the impact of enrofloxacin (ENR) on autotrophic, heterotrophic, and mixotrophic denitrification processes at various filling heights. The experiments were conducted across four consecutive phases with ENR concentrations of 0, 0.1, 1, and 10 mg/L. As the influent ENR concentration increased, the denitrification performance of the FeS2-based autotrophic denitrification (PAD) system was significantly inhibited at different filling heights, with nitrate removal efficiency (NrE) dropping to 30.42 %. In contrast, the polycaprolactone (PCL)-based heterotrophic denitrification (PHD) and mixotrophic denitrification (PAD+PHD) systems only affected NrE in the lower layer, whereas the middle and upper layers maintained high NrE levels, largely unaffected by ENR stress, reaching up to 98.28 % and 94.02 % respectively. Sulfate reduction was more prominent in the upper and middle layers of the mixotrophic denitrification bioreactor (PHD system). Bacterial diversity indices initially increased and then decreased as ENR concentration rose from 0 to 10 mg/L, with the PHD system showing lower diversity compared to the PAD system. Redundancy analysis (RDA) revealed that the relative abundances of Proteobacteria and Actinobacteriota in the PAD system, and Bacteroidota and Firmicutes in the PHD system, were negatively correlated with ENR concentration. Overall, the PAD system experienced significant stress from ENR at various filling heights, whereas the upper-middle layer of the PHD system demonstrated greater resistance. This highlighted the impact of antibiotic contamination along with the performance of different filling heights and emphasized the need for tailored strategies in wastewater treatment.

Innovative fixed bed bioreactor platform: Enabling linearly scalable adherent cell biomanufacturing with real-time biomass prediction from nutrient consumption.

Scalable single-use adherent cell-based biomanufacturing platforms are essential for unlocking the full potential of cell and gene therapies. The primary objective of this study is to design and develop a novel fixed bed bioreactor platform tailored specifically for scaling up adherent cell culture. The bioreactor comprises a packed bed of vertically stacked woven polyethylene terephthalate mesh discs, sandwiched between two-fluid guide plates. Leveraging computational fluid dynamics modeling, we optimized bioreactor design to achieve uniform flow with minimal shear stress. Residence time distribution measurements demonstrated excellent flow uniformity with plug flow characteristics. Periodic media sampling coupled with offline analysis revealed minimal gradients of crucial metabolites (glucose, glutamine, lactate, and ammonia) across the bioreactor during cell growth. Furthermore, the bioreactor platform demonstrated high performance in automated cell harvesting, with ≈96% efficiency and ≈98% viability. It also exhibited linear scalability in both operational parameters and performance for cell culture and adeno-associated virus vector production. We developed mathematical models based on oxygen uptake rates to accurately predict cell growth curves and estimate biomass in real-time. This study demonstrates the effectiveness of the developed fixed-bed bioreactor platform in enabling scalable adherent cell-based biomanufacturing with high productivity and process control.

Life cycle and efficiency assessment of fixed-bed bioreactor using recycled shredded plastics compared with conventional activated sludge bioreactor for dairy wastewater treatment

Adopting a highly efficient and low-cost bed bioreactor for the treatment of high-strength dairy wastewater has received unprecedented significance. Therefore, the concept of “waste as a resource” was brought up in this study and recycled shredded plastics (RSPs) were used to structure a fixed bed for activated sludge expansion. The performance of the RSP-attached growth system (AGS) and conventional suspended growth system (SGS) with intermittent anaerobic/aerobic conditions were scrutinized for dairy wastewater treatment. In addition, their environmental repercussions, greenhouse gas (GHG) emissions, and ecological footprint were explored to provide innovative insights into the field of research. The AGS system outperformed with substantial COD, nitrate, and phosphorus removal efficiencies (>89 %) in hydraulic retention time of 4 h, aeration time of 27 min, and COD/P ratio of 120. Notably, the SGS system outcompeted in the environmental impacts and energy usage, which accounted for 1.03–4.38 times higher than that for the AGS system. The electricity consumption and wastewater treatment process had striking roles in human carcinogenic toxicity, freshwater/marine ecotoxicity, and human health. The most required energy for AGS and SGS operations was supplied by fossil fuels, which increment GHG emissions from 4.31 to 8.77 kg CO2 eq for the AGS and SGS, respectively. Moreover, the reduction of electricity usage dramatically decreased human carcinogenic toxicity and marine ecotoxicity. Summing up, this study sheds light on the RSPs' capability to support activated sludge and ensure alignment with environmental criteria for dairy wastewater treatment.

Quasi-perfusion studies for intensified lentiviral vector production using a continuous stable producer cell line

Quasi-perfusion culture was employed to intensify lentiviral vector (LV) manufacturing using a continuous stable producer cell line in an 8-day process. Initial studies aimed to identify a scalable seeding density, with 3, 4, and 5 x 104 cells cm-2 providing similar specific productivities of infectious LV. Seeding at 3 x 104 cells cm-2 was selected, and the quasi-perfusion was modulated to minimise inhibitory metabolite accumulation and vector exposure at 37 °C. Similar specific productivities of infectious and physical LV were achieved at 1, 2, and 3 vessel volumes per day (VVD), with 1 VVD selected to minimise downstream processing volumes. The optimised process was scaled 50-fold to 1,264 cm2 flasks, achieving similar LV titres. However, scaling up beyond this to a 6,320 cm2 multilayer flask reduced titres, possibly from suboptimal gas exchange. Across three independent processes in 25 cm2 to 6,320 cm2 flasks, reproducibility was high with a coefficient of variation of (7.7 ± 2.9)% and (11.9 ± 3.0)% for infectious and physical LV titres, respectively. The optimised flask process was successfully transferred to the iCELLis™ Nano (Cytiva) fixed-bed bioreactor, with quasi-perfusion at 1 VVD yielding 1.62 x 108 TU.

Computational fluid dynamics based digital twins of fixed bed bioreactors validate scaling principles for recombinant adeno-associated virus gene therapy manufacturing.

Gene therapy using recombinant adeno-associated virus (rAAV) as delivery vehicles has garnered much interest in recent years. There are still significant gaps in our fundamental understanding of the manufacturing processes to deliver sufficient products. Manufacturing efforts of rAAV using HEK293 cells have commonly relied on fixed bed falling film bioreactors like the iCELLis®. We used computational fluid dynamics (CFD) to validate the operating conditions required for a predictive iCELLis® 500 scale-down model. The small-scale and at-scale systems have different flow paths causing validation of the corresponding agitation rates required to achieve the same linear flow through the fixed bed across scales to be non-trivial. Therefore, we used CFD to predict the theoretical scaling relationship. In addition, CFD could predict kLa differences between the two systems and the operating conditions required to match kLa between scales. We also confirmed that the location of DO control must be the same in both systems to achieve proper scaling. Experimental runs confirming the validity of the novel scale-down model showed that based on the modifications to the iCELLis® Nano system, we achieved similar DO, key metabolite, pH, and GC titer trends in both systems.

A comparative study on performance of the conventional and fixed-bed membrane bioreactors for treatment of Naproxen from pharmaceutical wastewater

Here, a comparative study was designed to survey the treatment efficiency of pharmaceutical wastewater containing Naproxen by Membrane bioreactor (MBR) and MBR with fixed-bed packing media (FBMBR). To this end, the performance of MBR and FBMBR in different aeration conditions including average DO (1.9–3.8 mg/L), different organic loading (OLR) (0.86, 1.14 and 1.92 kg COD per cubic meter per day), and Naproxen removal efficiency. The BOD5 removal efficiency, effluent quality and membrane fouling were monitored within 140 days. The results obtained from the present study indicated that COD removal efficiency for FBMBR (96.46%) was higher than that for MBR (95.33%). In addition, a high COD removal efficiency was experienced in both MBR and FBMBR in operational conditions 3 and 4, even where OLR increased from 1.14 to 1.92 kgCOD/m3 d and DO decreased from 4 to < 1 mg/L. Furthermore, the higher Naproxen removal efficiency was observed in FBMBR (94.17%) compared to that for MBR (92.76%). Therefore, FBMBR is a feasible and promising method for efficient treatment of pharmaceuptical wastewater with high concentrations of emerging contaminant, especially, the Naproxen.

Development and application of modified biocarrier immobilized with Bacillus sp. for azo dye degradation: batch and continuous study

The rapid growth of the industry and urbanization induces the consumption of large amounts of freshwater. In the meantime, untreated or partial treatment of industrial (especially textile) wastewater creates a threat to the living system. Azo dyes are generally used in textile industries and cause hazardous effects due to their recalcitrant and toxic nature. The present work emphasized the synergetic effect of adsorption and biodegradation of a modified biocarrier on Congo red (CR) dye removal. The modified biocarrier was developed by entrapping the polyurethane foam and activated carbon with sodium alginate. The adsorption effect was better explained by the Langmuir isotherm than Freundlich isotherm. Various independent factors, including pH, dissolved oxygen (DO), and dye concentration, were optimized in a fixed bed bioreactor (FBBR) filled with Bacillus sp. immobilized modified biocarrier. The highest removal of 95.43% was evaluated at a pH of 7.0, DO of 5.0 mg O2/L, and inlet CR dye concentration of 100 mg/L. Moreover, the continuous operation of FBBR achieved a 91.13% dye removal at an inlet loading rate of 216 mg/L. d at an initial dye concentration of 300 mg/L. The present approach could be an efficient technology for azo dye treatment.

Effect of salinity on denitrification, membrane fouling and bacterial community in a fixed-bed biofilm membrane reactor.

In this study, a fixed-bed biofilm membrane bioreactor was used to assess denitrification and carbon removal performance, membrane fouling, composition, and the dynamics of microbial communities across 10 salinity levels. As salinity levels increased (from 0 to 30 g/L), the removal efficiency of total nitrogen and chemical oxygen demand decreased from 98 and 86% in Phase I to 25 and 45% in Phase X, respectively. Beyond a salinity level of 10 g/L, membrane fouling accelerated considerably. The analysis of fouling resistance distribution suggested that soluble microbial products (SMPs) were the primary cause of this phenomenon. The irregularity in microbial community succession reflected the varying adaptability of different bacteria to different salinity levels. The relative abundance of Sulfuritalea, Lentimircobium, Thauera, and Pseudomonas increased from 20.2 to 47.7% as the experiments progressed. Extracellular polymeric substances-related analysis suggested that Azospirillum plays a positive role in preserving the structural integrity of the biofilm carrier. The SMP-related analysis showed a positive correlation between Lentimircobium, Thauera, Pseudomonas, and the SMP content. These results suggested that these three bacterial genera significantly promoted the release of SMP under salt stress, which in turn led to severe membrane fouling.

Continuous manufacturing of lentiviral vectors using a stable producer cell line in a fixed-bed bioreactor

Continuous manufacturing of lentiviral vectors (LVs) using stable producer cell lines could extend production periods, improve batch-to-batch reproducibility, and eliminate costly plasmid DNA and transfection reagents. A continuous process was established by expanding cells constitutively expressing third-generation LVs in the iCELLis™ Nano fixed-bed bioreactor. Fixed-bed bioreactors provide scalable expansion of adherent cells and enable a straightforward transition from traditional surface-based culture vessels. At 0.5 VVD (vessel volumes per day), the short half-life of LVs resulted in a low total infectious titre at 1.36 x 104 TU cm-2. Higher perfusion rates increased titres, peaking at 7.87 x 104 TU cm-2 at 1.5 VVD. The supernatant at 0.5 VVD had a physical-to-infectious particle ratio of 659, whereas this was 166 ± 15 at 1, 1.5, and 2 VVD. Reducing the pH from 7.20 to 6.85 at 1.5 VVD improved the total infectious yield to 9.10 x 104 TU cm-2. Three independent runs at 1.5 VVD and a culture pH of 6.85 showed low batch-to-batch variability, with a coefficient of variation of 6.4% and 10.0% for total infectious and physical LV yield, respectively. This study demonstrated the manufacture of high-quality LV supernatant using a stable producer cell line that does not require induction.

Optimization of aeration strategies for intensified nitrogen and phosphorus removal in an aerated electrolysis-assisted submerged fixed bed reactor treating recirculating mariculture effluent

Nutrients such as nitrogen (N) and phosphorus (P) discharged from mariculture wastewater pose a serious threat to the environment. In this study, an electrochemically assisted submerged fixed bed bioreactor (E-SFBBR) with intermittent aeration was used to explore the effect of aeration strategies (aeration time, aeration rate and aeration position) on the removal of N and P. Phosphate (PO43--P) removal was maintained above 95% under different aeration strategies. Although PO43--P removal predominantly occurred in the cathode areas, the aeration position affected the main functional area for PO43--P removal by influencing the pattern of DO distribution within E-SFBBR; and chemical precipitation with iron ions was the main removal pathway as revealed by XPS analysis. E-SFBBR with upper aeration (i.e., UA-E-SFBBR), aerated for 6 h d−1 at 0.8 L min−1 showed the best N removal performance, i.e., 83.78 ± 4.67%. The cathode area mainly contributed to N removal through mixotrophic denitrification. Aeration position plays a greater role in affecting N removal compared to aeration time and rate. Upper aeration favored the growth of heterotrophic denitrification bacteria (f_Rhodobacteraceae and Marinicella) in the cathode through providing more anaerobic environment, resulting in a better N removal performance. Besides, results of N transformation pathway predicted by PICRUSt 2.0 revealed that upper aeration promoted the ammonia assimilation but inhibited ammonia oxidation and NO3--N reduction processes in the cathode area. This study provided a theoretical basis for the application of aerated E-SFBBR in mariculture wastewater treatment.

Removal of emerging micropollutants from nanofiltration retentate of municipal wastewater within biological fixed-bed reactors under nitrifying and denitrifying conditions.

Municipal water resource recovery facilities are not designed to eliminate micropollutants, leading to many pollutants entering the aquatic environment. Within this study, as part of the project MicroStop, the biological treatment of nanofiltration effluent (retentate) under pure aerobic (without nitrification) as well as nitrifying and denitrifying conditions has been investigated for micropollutant elimination. A potential of further biotransformation under increased hydraulic retention time (HRT) of 14 days was shown. Under both HRT of 7 and 14 days, eliminations below LOQ were achieved in the aerated bioreactor for gabapentin, iomeprol, and metoprolol, reaching > 95%, > 69 to > 92%, and > 72%, respectively. The reduction of diclofenac was positively influenced by longer HRT leading to an elimination of up to 67%. Sulfamethoxazole was reduced under denitrification, but accumulated under aeration, resulting in fluctuating results and an overall elimination of 78% under 14 days HRT. PRACTITIONER POINTS: The micropollutant elimination in fixed-bed bioreactors of highly concentrated nanofiltration retentate was studied. Pure aerobic (without nitrification), nitrifying, and denitrifying conditions were investigated under hydraulic retention times (HRT) of 7 and 14 days. Higher initial pollutant concentrations enhanced the biological degradability in attached growth for substances being moderately degradable in activated sludge systems. 4A potential of further biological micropollutant elimination was shown for gabapentin, iomeprol, metoprolol, and diclofenac.

Continuous biocatalytic production of trehalose in a fixed-bed bioreactor using immobilized trehalose synthase from Pseudomonas stutzeri

The integrated approach of biocatalytic conversion coupled with purification using selective enzyme was developed to achieve continuous trehalose production. The activity of trehalose synthase (TS) derived from three different bacteria—Deinococcus radiodurans, Pseudomonas stutzeri, and Thermus thermophillus—immobilized with chitin-binding domain (ChBD-DrTS, ChBD-PsTS, and ChBD-TtTS, respectively) was compared for the production of trehalose from maltose syrup. The trehalose production yield using ChBD-PsTS was 2.4 and 1.7-fold higher than those using ChBD-DrTS and ChBD-TtTS, respectively, after 24 h at 30 °C and pH 7.0. In this study, a continuous bioconversion system was developed for trehalose production using ChBD-PsTS in a fixed-bed bioreactor, resulting in an approximate yield of 72%, and a productivity of 4 g/L/h. Additionally, residual maltose was converted into glucose using glucoamylase, and the 37% of bioethanol was produced. The integrated approach demonstrated remarkable biocatalytic performance, biocatalyst reusability, and high production yield.

Biooxidation of hydrogen sulfide to sulfur by moderate thermophilic acidophilic bacteria.

The copper industry utilizes significant amounts of sulfuric acid in its processes, generating sulfate as waste. While sulfate-reducing bacteria can remove sulfate, it produces hydrogen sulfide (H2S) as a byproduct. This study examined the capability of a consortium consisting of Sulfobacillus thermosulfidooxidans and Sulfobacillus acidophilus to partially oxidize H2S to S° at a temperature of 45°C. A fixed-bed bioreactor, with glass rings as support material and sodium thiosulfate as a model electron donor, was inoculated with the consortium. Formation of biofilms was crucial to maintain the bioreactor's steady state, despite high flow rates. Afterward, the electron donor was changed to H2S. When the bioreactor was operated continuously and with high aeration, H2S was fully oxidized to SO42-. However, under conditions of low aeration and at a concentration of 0.26g/L of H2S, the consortium was able to oxidize H2S to S° with a 13% yield. S° was discovered attached to the glass rings and jarosite. The results indicate that the consortium could oxidize H2S to S° with a 13% yield under low aeration and at a concentration of 0.26g/L of H2S. The findings highlight the capability of a Sulfobacillus consortium to convert H2S into S°, providing a potential solution for addressing environmental and safety issues associated with sulfate waste generated by the mining industry.

Effect of dissolved oxygen on the degradation activity and consumption capacity of white-rot fungi

In recent decades, bioremediation using white rot fungi (WRF) has become an attractive alternative for the removal of xenobiotics from water. However, WRF are aerobic microorganisms whose degradative capacity may be reduced when operating in oxygen-restricted environments. This work determines the limiting dissolved oxygen level of Trametes versicolor in terms of degradation of two target micropollutants: bentazon and tributyl phosphate. When the dissolved oxygen concentration was set below 15 % saturation (1.3 mg O2·L−1), the results revealed a considerable decrease in degradation capacity and laccase synthesis. Hence, 15 % dissolved oxygen was established as a reference value of aerobic conditions to assess dissolved oxygen profiles in both a rotating drum bioreactor (RDB) and a fixed-bed bioreactor (FBB). Restrictive oxygen conditions were achieved after an operating period of 24 h in the RDB and an empty bed contact time of 44 min in the FBB. In addition, growth kinetics on Q. ilex wood and organic matter removal (in terms of COD) were studied, obtaining 0.059 mg ergosterol·g wood DW−1·day−1 and 16.23 mg O2·L−1·h−1, respectively. Therefore, T. versicolor has demonstrated a remarkable ability to assimilate complex carbon sources and a high micropollutant degradation activity, especially when operating in non-limiting oxygen regimes.

Improved simultaneous nitrification–denitrification in fixed-bed baffled bioreactors treating mariculture wastewater: Performance and microbial community behaviors

As mariculture develops, wastewater treatment becomes crucial. In this study, fixed-bed baffled reactors (FBRs) packed with carbon fiber (CFBR) or polyurethane (PFBR) as biofilm carriers were used for mariculture wastewater treatment. Under salinity shocks between 0.10 and 30.00 g/L, the reactors showed efficient and stable nitrogen removal capacities, and the maximum NH4+-N removal rates were 107.31 and 105.42 mg/(L·d) for CFBR and PFBR, respectively, with an initial NH4+-N concentration of 120.00 mg/L. Further, in the independent aerobic chambers of the FBRs for nitrogen removal, taxa enrichment varied depending on the biofilm carrier, and the assembly process was more deterministic in CFBR than in PFBR. Two distinct clusters representing the spatial distribution of the adhering and deposited sludge in CFBR and the front and rear compartments in PFBR were noted. Furthermore, microbial interactions were more numerous and stable in CFBR. These findings improve the application prospects of FBRs in mariculture wastewater treatment.

Bio-precipitation of arsenic and antimony in a sulfate-reducing bioreactor treating real acid mine drainage water.

Arsenic (As) and antimony (Sb) from mining sites can seep into aquatic ecosystems by acid mine drainage (AMD). Here, the possibility of concomitantly removing As and Sb from acidic waters by precipitation of sulfides induced by sulfate-reducing bacteria (SRB) was investigated in a fixed-bed column bioreactor. The real AMD water used to feed the bioreactor contained nearly 1 mM As, while the Sb concentrations were increased (0.008 ± 0.006 to 1.01 ± 0.07 mM) to obtain an Sb/As molar ratio = 1. Results showed that the addition of Sb did not affect the efficiency of As bio-precipitation. Sb was removed efficiently (up to 97.9% removal) between the inlet and outlet of the bioreactor, together with As (up to 99.3% removal) in all conditions. Sb was generally removed as it entered the bioreactor. Appreciable sulfate reduction occurred in the bioreactor, which could have been linked to the stable presence of a major SRB operational taxonomic unit affiliated with the Desulfosporosinus genus. The bacterial community included polymer degraders, fermenters, and acetate degraders. Results suggested that sulfate reduction could be a suitable bioremediation process for the simultaneous removal of Sb and As from AMD.