Layered double hydroxide modified biochar combined with sodium alginate: A powerful biomaterial for enhancing bioreactor performance to remove nitrate

Carbon slow-release and enhanced nitrogen removal performance of plant residue-based composite filler and ecological mechanisms in constructed wetland application

Stable carbon release and coupled microbial efficacy of external carbon source solid fillers are the keys to enhanced nitrogen removal in constructed wetlands. The constructed wetland plant residue Acorus calamus was cross-linked with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) to create composite solid carbon source fillers (Ac-BDPs). The study demonstrated the slow release of carbon sources from Ac-BDPs with 35.27 mg/g under an average release rate of 0.88 mg/(g·d). Excellent denitrification was also observed in constructed wetlands with Ac-BDPs. Moreover, the average removal rate of nitrate nitrogen (NO3--N) was increased by 1.94 and 3.85 times of the blank groups under initial NO3--N inputs of 5 and 15 mg/L, respectively. Furthermore, the relatively high abundances of nap, narG, nirKS, norB, qnorZ and nosZ guaranteed efficient denitrification performance in constructed wetlands with Ac-BDPs. The study introduced a reliable technique for biological nitrogen removal by using composite carbon source fillers in constructed wetlands.

Biochar inoculated with Rhodococcus biphenylivorans altered microecological regulation by promoting quorum sensing and electron transfer: Up-regulation of related genes and enhancement of phenol and ammonia degradation

Bioaugmentation is an efficient method for improving the efficiency of coking wastewater removal. Nevertheless, how different immobilization approaches affect the efficiency of bioaugmentation remains unclear, as does the corresponding mechanism. With the assistance of immobilized bioaugmentation strain Rhodococcus biphenylivorans B403, the removal of synthetic coking wastewater was investigated (drying agent, alginate agent, and absorption agent). The reactor containing the absorption agent exhibited the highest average removal efficiency of phenol (99.74 %), chemical oxygen demand (93.09 %), and NH4+-N (98.18 %). Compared to other agents, the covered extracellular polymeric substance on the absorption agent surface enhanced electron transfer and quorum sensing, and the promoted quorum sensing benefited the activated sludge stability and microbial regulation. The phytotoxicity test revealed that the wastewater's toxicity was greatly decreased in the reactor with the absorption agent, especially under high phenol concentrations. These findings showed that the absorption agent was the most suitable for wastewater treatment bioaugmentation.

Effect of biochars on the immobilization and form of Cadmium (Cd) in simulated Cd deposition of iron rich soils

Atmospheric deposition of Cd poses a serious threat to ecosystem security. Biochar is widely used for polluted soil remediation, however, whether biochar already applied to the soil can reduce the hazards of newly deposited Cd remains to be studied. Thus, an indoor cultural experiment and static adsorption method were conducted to study the isothermal and kinetic adsorption processes of three types of biochar (rice husk, rubber wood, and tobacco stem biochars) on Cd in iron rich soils and the effect of biochar on the morphological distribution of Cd in the soil and the soil pH. The results showed that the soil with biochar in our study could quickly fix "the new deposited Cd" in the soil in 3 h with the maximum adsorption capacity in rubber wood biochar-treated sample (3227.34 mg/kg）. The addition of all three biochar treatments significantly increased the soil pH and reduced the soil exchange state Cd content, with a 13.69-17.32% increase in the pH and a 13.22-54.39% reduction in the exchange state Cd content when contrasted with the control, which could promote those Cd converting into unavailable Cd (carbonate-bound form Cd, Fe-Mn oxide-bound form Cd, or residual form Cd) for crops. In summary, the addition of three kinds of biochar treatments could effectively reduce the ecological and environmental risk of soil that was contaminated by Cd and could provide a reliable theoretical basis for the effect of biochar on the improvement of the quality of soil that is contaminated by heavy metals.

Bacterial cellulose as a reinforcement material of alginate beads improves effectiveness and recycling potential of immobilized photosynthetic bacteria for cooking oil waste removal

The rapid degradation of alginate beads limits the lifespan of immobilized cells. In this study, bacterial cellulose (BC) incorporated in alginate was used to improve the mechanical properties, swelling ratio, and recycling time of the immobilized photosynthetic bacterium Rhodopseudomonas faecalis PA2 for the removal of cooking oil residues. Beads reinforced with 25 and 50% BC showed a higher Young's modulus and compressive strength and a lower swelling ratio than the control treatment (0% BC). The incorporation of 50% BC increased biomass production and oil removal. Field-emission scanning electron microscopy revealed several bacteria-infested internal pores in the reinforced beads, indicating bacterial growth in the presence of BC. Bacterial viability was verified by BC immersion in the bacterial culture broth and by injecting bacteria into the BC matrix. Without BC reinforcement, beads collapsed after reuse in two batches, whereas reinforced beads could be reused for five batches, resulting in an oil removal rate of up to 76.3 %. Our results show that BC can be used as an alginate reinforcing material to improve bead stability and prolong the effective recycling period of immobilized bacteria without negatively affecting bacterial growth or waste oil removal.

Recent progress in the production and application of biochar and its composite in environmental biodegradation

Over the past few decades, extensive research has been conducted to develop cost-effective and high-quality biochar for environmental biodegradation purposes. Pyrolysis has emerged as a promising method for recovering biochar from biomass and waste materials. This study provides an overview of the current state-of-the-art biochar production technology, including the advancements and biochar applications in organic pollutants remediation, particularly wastewater treatment. Substantial progress has been made in biochar production through advanced thermochemical technologies. Moreover, the review underscores the importance of understanding the kinetics of pollutant degradation using biochar to maximize its synergies for potential environmental biodegradation. Finally, the study identifies the technological gaps and outlines future research advancements in biochar production and its applications for environmental biodegradation.

Modified alginate materials for wastewater treatment: Application prospects

Sodium alginate is a natural macromolecule widely used because of its abundance, low cost of acquisition, and rich hydroxyl and carboxyl groups in the matrix. The physical modification of sodium alginate can be made by blending it with polymer materials. The so-yielded alginate complex is commonly unstable in an aqueous environment due to alginate backbones' high hydrophilicity. The chemical modification can remove its hydrophilic groups and introduce special functional groups or polymers onto the alginate backbones to provide excess reaction sites for specific reactions and effective complexation sites for accommodating antibiotics, dyes, heavy metal ions, and radioactive elements. Sodium alginate has been used in water treatment engineering under revised modification protocols. This article also reviews the latest modification protocols for sodium alginate and outlines the novel application of the modified materials. The limitations of modified sodium alginate materials are described, and research prospects are put forward.

The potential of biochar as a microbial carrier for agricultural and environmental applications

Biochar can be an effective carrier for microbial inoculants because of its favourable properties promoting microbial life. In this review, we assess the effectiveness of biochar as a microbial carrier for agricultural and environmental applications. Biochar is enriched with organic carbon, contains nitrogen, phosphorus, and potassium as nutrients, and has a high porosity and moisture-holding capacity. The large number of active hydroxyl, carboxyl, sulfonic acid group, amino, imino, and acylamino hydroxyl and carboxyl functional groups are effective for microbial cell adhesion and proliferation. The use of biochar as a carrier of microbial inoculum has been shown to enhance the persistence, survival and colonization of inoculated microbes in soil and plant roots, which play a crucial role in soil biochemical processes, nutrient and carbon cycling, and soil contamination remediation. Moreover, biochar-based microbial inoculants including probiotics effectively promote plant growth and remediate soil contaminated with organic pollutants. These findings suggest that biochar can serve as a promising substitute for non-renewable substrates, such as peat, to formulate and deliver microbial inoculants. The future research directions in relation to improving the carrier material performance and expanding the potential applications of this emerging biochar-based microbial immobilization technology have been proposed.

Efficient removal of tetracycline from aqueous solution by K2CO3 activated penicillin fermentation residue biochar

In this study, biochar was prepared using penicillin fermentation residue (PR) as the raw material by different methods. The adsorption behavior and adsorption mechanism of biochar on tetracycline (TC) in an aqueous environment were investigated. The results showed that K₂CO₃ as an activator could effectively make porous structures, and that biochar with mesoporous or microporous could be prepared in a controlled manner with two kinds of different activation methods, the dry mixing method and the impregnation method. The dry mixing method could create more mesopores, while the impregnation method could prepare more micropores. Microporous biochar (IKBCH) with a high specific surface area could be prepared by the impregnation method combined with HCl soaking, which has an excellent adsorption effect on tetracycline. When the concentration of tetracycline was 200 mg/L, the removal rate of 99.91% could be achieved with the dosage of microporous biochar at 1 g/L. The adsorption process was in accordance with the Langmuir model and the pseudo-second-order model, respectively. The maximum adsorption capacity of IKBCH was 268.55 mg/g (25°C). The adsorption mechanisms were pore filling, π-π interaction, electrostatic adsorption, and hydrogen bond. Its stable and wide applicability adsorption process does not cause ecological pollution in the aqueous environment, and it is a promising biochar adsorbent.

Application of biochar immobilized microorganisms for pollutants removal from wastewater: A review

Microbial immobilization technology (MIT) has been rapidly developed and used to remove pollutants from water/wastewater in recent years, owing to its high stability, rapid reaction rate, and high activity. Microbial immobilization carrier with low cost and high removal efficiency is the key of MIT. Biochar is considered to be an efficient carrier for microbial immobilization because of its high porosity and good adsorption effect, which can provide a habitat for microorganisms. The use of biochar immobilized microorganisms to treat different pollutants in wastewater is a promising treatment method. Compared with the other biological treatment technology, biochar immobilized microorganisms can improve microbial abundance, repeated utilization ratio, microbial metabolic capacity, etc. However, current research on this method is still in its infancy. Little attention has been paid to the interaction mechanisms between biochar and microorganisms, and many studies are only carried out in the laboratory. There are still problems such as difficult recovery after use and secondary pollution caused by residual pollutants after biochar adsorption, which need further clarification. To have comprehensive digestion and an in-depth understanding of biochar immobilized microorganisms technology in wastewater treatment, the wastewater treatment methods based on biochar are firstly summarized in this review. Then the mechanisms of immobilized microorganisms were explored, and the applications of biochar immobilized microorganisms in wastewater were systematically reviewed. Finally, suggestions and perspectives for future research and practical application are put forward.

Adsorption of nitrate from interflow by the Mg/Fe calcined layered double hydroxides

Nitrate loss in interflow caused serious nitrate pollution of neighboring water bodies in the purple soil region of China's Sichuan Province. In this study, Mg/Fe(Al)-calcined layered double hydroxides (Mg/Fe(Al)-CLDHs) with varied Mg/Fe(Al) ratios were synthesized for nitrate removal from interflow, and 3:1 Mg/Fe CLDH exhibited the best adsorption performance. The effects of initial pH, adsorbent dosage and co-existing anions on the adsorption performance were investigated by batch experiments. The best-fitting kinetic and isothermal models for nitrate adsorption were the pseudo-second-order model and Freundlich model, respectively, indicating that the adsorption process was a physical-chemical multilayer process. The maximum adsorption capacity of nitrate was 73.36 mg/g, which was higher than that of many other commonly used adsorbents. The adsorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) techniques, and the XRD and FT-IR results revealed that the adsorption mechanism involved original layered structure reconstruction and ion-exchange interaction. Under the coexistence of SO₄^2- and Cl^-, 75.63% nitrate in interflow could be removed after 6 h of adsorption. Overall, the synthesized Mg/Fe CLDH is an effective and low-cost nitrate adsorbent for in-situ nitrate removal.

Removal of phosphorus using biochar derived from Fenton sludge: Mechanism and performance insights

A phosphorus removal biochar adsorbent was prepared from Fenton sludge. The adsorption process was optimized, and its phosphorus adsorption mechanism was discussed. It was found that the phosphorus adsorption performance of biochar prepared from single Fenton sludge (FBC-400) was better than that of co-pyrolysis of Fenton sludge and bamboo powder. The optimum condition was that Fenton sludge pyrolyzed at 400°C (FBC-400). FBC-400 had a larger specific surface area than that prepared by co-pyrolysis with bamboo powder. And the high content of iron element could provide a higher surface charge of the biochar, thereby increasing the electrostatic adsorption of phosphorus onto FBC-400. The phosphorus adsorption was highly pH dependent by FBC-400, which can enhance electrostatic adsorption and increase adsorption capacity in acidic conditions. The effect of coexisting anion on adsorption performance was mainly affected by CO₃ ^2- , reducing the adsorption capacity by at least 49%, whereas other anions had no obvious interference. The adsorption process of FBC-400 accorded with the pseudo-second-order kinetic model and the Langmuir model, which indicated that the adsorption process was monolayer adsorption and mainly chemical adsorption, and the maximum saturated phosphorus adsorption capacity was 8.77 mg g^-1 . The mechanisms for phosphorus adsorption were electrostatic adsorption and inner-sphere complexing. 1 M NaOH was used for desorption, and the adsorption capacity remained at 81% in the fifth cycle. PRACTITIONER POINTS: The Fenton sludge biochar usage as an adsorbent could be a win-win strategy to convert waste biomass to valuable - product. The adsorption process accorded with the Langmuir model, the maximum phosphorus adsorption capacity was 8.77 mg/g at 25°C. The adsorption mechanisms were electrostatic adsorption and inner-sphere complexing. 1M NaOH was used for desorption, and the adsorption capacity remained at 81% in the fifth cycle.

Bioaugmented removal of 17β-estradiol, nitrate and Mn(II) by polypyrrole@corn cob immobilized bioreactor: Performance optimization, mechanism, and microbial community response

The coexistence of nitrate and endocrine substances (EDCs) in groundwater is of global concern. Herein, an efficient and stable polypyrrole@corn cob (PPy@Corn cob) bioreactor immobilized with Zoogloea sp. was designed for the simultaneous removal of 17β-estradiol (E2), nitrate and Mn(II). After 225 days of continuous operation, the optimal operating parameters and enhanced removal mechanism were explored, also the long-term toxicity and microbial communities response mechanisms under E2 stress were comprehensively evaluated. The results showed that the removal efficiencies of E2, nitrate, and Mn(II) were 84.21, 82.96, and 47.91%, respectively, at the optimal operating conditions with hydraulic retention time (HRT) of 8 h, pH of 6.5 and Mn(II) concentration of 20 mg L^-1. Further increased of initial E2 (2 and 3 mg L^-1) resulted in the inhibiting effect of denitrification and manganese oxidation, but excellent E2 removal efficiencies maintained, which were associated with the formation and continuous accumulation of biomanganese oxides (BMO). Characterization analysis of biological precipitation demonstrated that adsorption and redox conversion on the BMO surface played key roles in the removal of E2. In addition, different levels of E2 exposure are decisive factors in community evolution, and bioaugmented bacterial communities with Zoogloea as the core group can dynamically adapt to E2 stress. This study offers the possibility to better utilize microbial metabolism and to advance opportunities that depend on microbial physiology and material characterization applications.

A Comprehensive Review of Layered Double Hydroxide-Based Carbon Composites as an Environmental Multifunctional Material for Wastewater Treatment

As is well known, hydrotalcite-like compounds, such as layered-double-hydroxide (LDH) materials, have shown great potential applications in many fields owing to their unique characteristics, including a higher anion exchange capacity, a structure memory effect, low costs, and remarkable recyclability. While the lower surface area and leaching of metal ions from LDH composites reduce the process efficiency of the catalyst, combining LDH materials with other materials can improve the surface properties of the composites and enhance the catalytic performance. Among organic compounds, carbon materials can be used as synergistic materials to overcome the defects of LDHs and provide better performance for environmental functional materials, including adsorption materials, electrode materials, photocatalytic materials, and separation materials. Therefore, this article comprehensively reviews recent works on the preparation and application of layered double-hydroxide-based carbon (LDH–C) composites as synergistic materials in the field of environmental remediation. In addition, their corresponding mechanisms are discussed in depth. Finally, some perspectives are proposed for further research directions on exploring efficient and low-cost clay composite materials.

Lead adsorption and antibacterial activity using modified magnetic biochar/sodium alginate nanocomposite

Biochar is one of the most promising wastewater treatment materials. As shown in the Scanning Electron Micrograph, the magnetic biochar (BC) cross-linked glutaraldehyde (G) with sodium alginate (SA) (BC-G-SA) nanocomposite formed with uniform particle size without aggregation, and an X-Ray Diffraction study revealed that the BC-G-SA nanocomposite has an amorphous structure. The BC-G-SA nanocomposite enhanced the microwave adsorption process for Pb (II). The maximum metal capacity value was obtained using the microwave adsorption technique at pH 5.0 and contact time 20 s for Pb (II) at medium and low microwave power (940 and 1400 μmol g^-1, respectively). Pb (II) adsorption isotherm follows a pseudo-second-order model. Also, the BC-G-SA nanocomposite effectively inhibited bacterial growth throughout the growth kinetics experiment. BC-G-SA inhibited the growth of S. aureus at a MIC of 200 g mL^-1, whereas L. monocytogenes had a MIC of 200 g mL^-1. The MIC values for E. faecalis and E. faecium were significantly lower (50 and 100 g mL^-1, respectively).

Nitrate removal under low carbon to nitrogen ratio by modified corn straw bioreactor: Optimization and possible mechanism

ABSTRACTThe removal of nitrate (NO₃^--N) from water bodies under the conditions of poor nutrition and low carbon to nitrogen (C/N) ratio is a widespread problem. In this study, modified corn stalk (CS) was used to immobilize Burkholderia sp. CF6 with cellulose-degrading and denitrifying abilities. The optimal operating parameters of the bioreactor were explored. The results showed that under the hydraulic retention time (HRT) of 3 h and the C/N ratio of 2.0, the maximum nitrate removal efficiency was 96.75%. In addition, the organic substances in the bioreactor under different C/N ratios and HRT were analyzed by three-dimensional fluorescence excitation-emission mass spectrometry (3D-EEM), and it was found that the microorganisms have high metabolic activity. Scanning electron microscope (SEM) showed that the new material has excellent immobilization effects. Fourier transform infrared spectrometer (FTIR) showed that it has potential as a solid carbon source. Through high-throughput sequencing analysis, Burkholderia sp. CF6 was observed as the main bacteria present in the bioreactor. These research results showed that the use of waste corn stalks waste provides a theoretical basis for the advanced treatment of low C/N ratio wastewater.

Removal of heavy metals from wastewaters with biochar pyrolyzed from MgAl-layered double hydroxide-coated rice husk: Mechanism and application

This study reports a MgAl-LDH rice husk biochar composite (MgAl-LDH@RHB) with a regular hydrotalcite structure synthesized by a simple hydrothermal method, which was then used to remove Cd(II) and Cu(II) from water. The influencing factors on the adsorption performance were determined through batch adsorption experiments, and the adsorption characteristics and cycling capacity were evaluated with eight models and adsorption-desorption experiments. The results showed that the adsorption of Cd(II) and Cu(II) by MgAl-LDH@RHB conformed to the Langmuir-Freundlich model and PSO kinetics model, indicating single-layer chemical adsorption. In addition, the experimental maximum adsorption capacities for Cd(II) and Cu(II) were 125.34 and 104.34 mg g^-1, respectively. The adsorption of Cd(II) and Cu(II) by MgAl-LDH@RHB was dominated by surface precipitation and ion exchange. The findings reveal the mechanism for the heavy metal removal by MgAl-LDH@RHB and provide a theoretical reference for agricultural waste disposal and water pollution control.

Enhancement of denitrification in biofilters by immobilized biochar under low-temperature stress

Efficient removal of nitrate under low temperature is challenging because of the reduction of the microbial activity. This study successfully explored the promotion on the performance of denitrification utilizing the immobilized biochar in biofilters under low temperature (6 ± 2 °C). The results showed that the immobilized biochar increased the denitrification rate by 76.8% and decreased the nitrous oxide emissions by 82.5%. Mechanistic studies revealed that the immobilized biochar increased the activities of the denitrifying enzymes and three enzymes involved in glycolysis. Furthermore, the immobilized biochar elevated the activity of the electron transport system by 31.8%. Finally, structural equation model explained that the increase of nitrate reductase activity was a crucial factor to enhance the total nitrogen removal efficiency in biofilters with immobilized biochar. Overall, the use of immobilized biochar can be a novel strategy to enhance nitrogen removal and reduce greenhouse gas emissions in biofilters under low temperature.

Biochar/Mg-Al spinel carboxymethyl cellulose-La hydrogels with cationic polymeric layers for selective phosphate capture

Recently, biochar-related phosphate sorbents have been extensively investigated and achieved significant progress; however, there is still much room for enhancement on capturing performance and recovery of powdery ones after sorption. Herein, a new kind of adsorbent, in which biochar/Mg-Al spinel encapsulated in carboxymethyl cellulose-La hydrogels with cationic polymeric layers, was fabricated, aiming for integrating multi-advantages of each component for enhanced phosphate capture. Batch static experiments were correlated to the phosphate adsorption performance of the adsorbent. The maximum phosphate adsorption capacity of the adsorbent was 89.65 mg P/g at pH = 3. The Langmuir isotherm model and the pseudo-second-order kinetic model fitted well with the adsorption behavior of the adsorbent. More importantly, this composite adsorbent that integrated with biochar, Mg-Al spinel, cationic polymeric components exhibited favorable selectivity over coexisting anions (Cl^-, SO₄^2-, HCO₃^- and NO₃^-) and performed good reusability after five consecutive cycles. By virtue of the bead-like feature, fixed-bed column experiments demonstrated that the Thomas model fitted the breakthrough curves well under varied experimental conditions. The adsorption mechanism of phosphate on the designed composite adsorbent with multi-components could be described as the electrostatic attraction, ligand exchange and inner-sphere complexation, which might account for the efficient phosphate capturing performance.

Self-immobilized biochar fungal pellet combined with bacterial strain H29 enhanced the removal performance of cadmium and nitrate

A newly isolated strain Phoma sp. ZJ6, which could form fungal pellet (FP) by self-immobilization, was identified. A novel longan seed biochar embedded in FP (BFP) combined with strain H29 (BFP-H29) effectively improved the Cd(II) removal efficiency and simultaneously removed nitrate. The adsorption process of BFP was well fitted with the pseudo-second-order kinetics model and Langmuir isotherm model, which demonstrated that the adsorption process was favorable and mainly dominated by chemisorption. Compared with single FP, biochar, and strain H29, BFP-H29 significantly enhanced the Cd(II) removal and the removal ratio reached 90.47%. Meanwhile, the simultaneous removal efficiency of the BFP-H29 for nitrate could reach 93.80%. Characterization analysis demonstrated that the primary removal mechanisms of BFP-H29 were precipitation and surface complexation. BFP-H29 had excellent performance in simultaneous removal of Cd(II) and nitrate, indicating its potential as a promising composite in the removal of cadmium and nitrate in wastewater.

Application of layered double hydroxide-biochar composites in wastewater treatment: Recent trends, modification strategies, and outlook

In recent years, layered double hydroxide-biochar (LDH-BC) composites as adsorbents and catalysts for contaminants removal (inorganic anions, heavy metals, and organics) have received increasing attention and became a new research point. It is because of the good chemical stability, abundant surface functional groups, excellent anion exchange ability, and good electronic properties of LDH-BC composites. Hence, we offer an overall review on the developments and processes in the synthesis of LDH-BC composites as adsorbents and catalysts. Special attention is devoted to the strategies for enhancing the properties of LDH-BC composites, including (1) magnetic treatment, (2) acid treatment, (3) alkali treatment, (4) controlling metal ion ratios, (5) LDHs intercalation, and (6) calcination. In addition, further studies are called for LDH-BC composites and potential areas for future application of LDH-BC composites are also proposed.

Fungal pellets immobilized bacterial bioreactor for efficient nitrate removal at low C/N wastewater

In this study, fungal pellets immobilized denitrifying Pseudomonas stutzeri sp. GF3 was cultivated to establish a bioreactor. The denitrification effect of fixed bacteria with fungal pellets was tested by response surface methodology (RSM). Analysis of the bioreactor showed that the denitrification efficiency reached 100% under the optimal conditions and the denitrification efficiency of the actual wastewater treatment in the stable phase reached 95.91%. Moreover, the organic matter and functional groups in the bioreactor under different C/N conditions were analyzed by fluorescence excitation-emission matrix (EEM) spectra and Fourier transform infrared spectroscopy (FTIR), which revealed that metabolic activities of denitrifying bacteria were enhanced with the increase of C/N. The morphology and structure of bacteria immobilized by fungal pellets explored by scanning electron microscope (SEM) showed the filamentous porous fungal pellets loaded with bacteria. Community structure analysis by high-throughput sequencing demonstrated that strain GF3 might was the dominant strain in bioreactor.

Efficient removal of nitrate, manganese, and tetracycline by a polyvinyl alcohol/sodium alginate with sponge cube immobilized bioreactor

The co-existence of nitrate, manganese (Mn), and antibiotics are of a wide concern. In this study, a denitrifying and manganese-oxidizing Zoogloea Q7 bacterium was immobilized using polyvinyl alcohol/sodium alginate with sponge cube (PVA/SA@sponge cube) in the reactor. The optimal operation parameters of the bioreactor were explored. Maximum nitrate, Mn(II), and tetracycline (TC) removal efficiencies of 93.00, 72.34, and 57.32% were achieved with HRT of 10 h, pH of 6.5, Mn(II) concentration of 20 mg L^-1, and TC of 1 mg L^-1, respectively. Fluorescence excitation-emission matrix (EEM) proved that the microorganism in the bioreactor was greatly active. Scanning electron microscope (SEM) images demonstrated that Zoogloea Q7 was commendably immobilized on the novel material. X-ray diffraction (XRD) analysis suggested that the bioprecipitate was mainly composed of MnO₂ and MnCO_3. Through high-throughput analysis, Zoogloea sp. Q7 was considered to be the dominant bacteria present in the bioreactor.