Bioaugmentation of Moving Bed Biofilm Reactor (MBBR) with Achromobacter JL9 for enhanced sulfamethoxazole (SMX) degradation in aquaculture wastewater

Metagenomic insights into effects of carbon/nitrogen ratio on microbial community and antibiotic resistance in moving bed biofilm reactor

This study investigated the effects of carbon/nitrogen (C/N) ratio on microbial community in moving bed biofilm reactor (MBBR) using metagenomic analysis, and the dynamic changes of relevant antibiotic resistance genes (ARGs) were also analyzed. The results showed that under low C/N ratio, MBBR exhibited average removal rates of 98.41 % for ammonia nitrogen and 75.79 % for total nitrogen. Metagenomic analysis showed low C/N ratio altered the structure of biofilm and water microbiota, resulting in the detachment of bacteria such as Actinobacteria from biofilm into water. Furthermore, sulfamethazine (SMZ)-resistant bacteria and related ARGs were released into water under low C/N ratio, which lead to the increase of SMZ resistance rate to 90%. Moreover, most dominant genera are potential hosts for both nitrogen cycle related genes and ARGs. Specifically, Nitrosomonas that carried gene sul2 might be released from biofilm into water. These findings implied the risks of antibiotic resistance dissemination in MBBR under low C/N ratio.

Cytoprotective alginate microcapsule serves as a shield for microalgal encapsulation defensing sulfamethoxazole threats and safeguarding nutrient recovery

Microalgal encapsulation technology is expected to broaden more possibilities for employing microalgae for upgrading conventional biological wastewater treatment. However, only limited and fragmented information is currently available on microalgal encapsulation and pollutant removal. It is ambiguous whether it hold potential for wastewater treatment. Particularly, it remains to be determined whether this technology can provide more possibilities in harsh sewage environments. Here, potential of encapsulated technology to recover nutrients from wastewater was examined, simultaneously compared with commonly adopted suspended system. Results indicate the encapsulated microalgal system showed outstanding advantages in nutrient recovery and defense against antibiotic threats. Moreover, by examining the cellular oxidative stress response and changes of the photosynthetic system, the encapsulated system exhibited potential cytoprotective advantages to microalgal cells for defensing antibiotic threats. Molecular dynamics simulation revealed that the differences among superficial aggregation between the nutrients' ions and molecular sulfamethoxazole on the cross-linked alginate microcapsule surface dominated the nutrient recovery and cytoprotective functions. Ultimately, the molecular nature of pollutants was found to be the most critical aspect for predicting application of this microalgal microcapsule. Cytoprotective systems created with alginate microcapsules can potentially handle more diverse threats with a single type of surface charge in their outermost layer.

New insights into bioaugmented removal of sulfamethoxazole in sediment microcosms: degradation efficiency, ecological risk and microbial mechanisms

BACKGROUND

Bioaugmentation has the potential to enhance the ability of ecological technology to treat sulfonamide-containing wastewater, but the low viability of the exogenous degraders limits their practical application. Understanding the mechanism is important to enhance and optimize performance of the bioaugmentation, which requires a multifaceted analysis of the microbial communities. Here, DNA-stable isotope probing (DNA-SIP) and metagenomic analysis were conducted to decipher the bioaugmentation mechanisms in stabilization pond sediment microcosms inoculated with sulfamethoxazole (SMX)-degrading bacteria (Pseudomonas sp. M2 or Paenarthrobacter sp. R1).

RESULTS

The bioaugmentation with both strains M2 and R1, especially strain R1, significantly improved the biodegradation rate of SMX, and its biodegradation capacity was sustainable within a certain cycle (subjected to three repeated SMX additions). The removal strategy using exogenous degrading bacteria also significantly abated the accumulation and transmission risk of antibiotic resistance genes (ARGs). Strain M2 inoculation significantly lowered bacterial diversity and altered the sediment bacterial community, while strain R1 inoculation had a slight effect on the bacterial community and was closely associated with indigenous microorganisms. Paenarthrobacter was identified as the primary SMX-assimilating bacteria in both bioaugmentation systems based on DNA-SIP analysis. Combining genomic information with pure culture evidence, strain R1 enhanced SMX removal by directly participating in SMX degradation, while strain M2 did it by both participating in SMX degradation and stimulating SMX-degrading activity of indigenous microorganisms (Paenarthrobacter) in the community.

CONCLUSIONS

Our findings demonstrate that bioaugmentation using SMX-degrading bacteria was a feasible strategy for SMX clean-up in terms of the degradation efficiency of SMX, the risk of ARG transmission, as well as the impact on the bacterial community, and the advantage of bioaugmentation with Paenarthrobacter sp. R1 was also highlighted. Video Abstract.

Triclocarban-contaminated wastewater treatment by innovative hybrid moving entrapped bead activated sludge reactor (HyMER): Continuous performance and computational dynamic simulation analysis

Triclocarban (TCC) has been used in consumer products and is a widespread contaminant in municipal wastewater treatment systems that ultimately accumulates in natural receiving water and soil. This work aims to apply an innovative hybrid moving entrapped bead activated sludge reactor (named "HyMER") that integrates entrapped TCC-degrading microbes and freely suspended activated sludge to treat TCC-contaminated wastewater. A previously isolated TCC-degrading bacterium (Pseudomonas fluorescens strain MC46, called MC46) and barium alginate entrapment were applied. The synthetic TCC-contaminated wastewater treatment (with TCC concentration of 10 mg/L) was performed using 20-cycle fed-batch reactor operation with feeding times of 12 and 24 h and cycle times of 13 and 25 h. The results indicated that the HyMER effectively reduced chemical oxygen demand by up to 80 and 95 % and TCC by up to 53 and 83 %, respectively, with feeding times of 12 and 24 h. Three TCC degradation intermediate products were found-3,4-dichloroaniline, 4-chloroaniline, and aniline. Scanning electron microscopic analysis revealed shorter cells and bacterial appendage development as cell adaptations against TCC and its intermediates. The live/dead assay indicated high survival of entrapped MC46 in toxic conditions, with up to 84 % viable cells. Based on computational fluid dynamic analysis, no entrapped cell agglomeration showed in the reactor, indicating the potential application of HyMER for real wastewater treatment. These results exhibit the feasibility of HyMER and its applicability for future toxic wastewater treatment.

Analysis of the Comparative Growth Kinetics of Paenarthrobacter ureafaciens YL1 in the Biodegradation of Sulfonamide Antibiotics Based on Substituent Structures and Substrate Toxicity

The high consumption and emission of sulfonamide antibiotics (SAs) have a considerable threat to humans and ecosystems, so there is a need to develop safer and more effective methods than conventional strategies for the optimal removal of these compounds. In this study, four SAs with different substituents, sulfadiazine (SDZ), sulfamerazine (SMR), sulfamethoxazole (SMX), and sulfamethazine (SMZ) were removed by a pure culture of Paenarthrobacter ureafaciens YL1. The effect of the initial SAs concentration on the growth rate of strain YL1 was investigated. The results showed that the strain YL1 effectively removed various SAs in the concentration range of 0.05–2.4 mmol·L−1. The Haldane model was used to perform simulations of the experimental data, and the regression coefficient of the model indicated that the model had a good predictive ability. During SAs degradation, the maximum specific growth rate of strain YL1 was ranked as SMX > SDZ > SMR > SMZ with constants of 0.311, 0.304, 0.302, and 0.285 h−1, respectively. In addition, the biodegradation of sulfamethoxazole (SMX) with a five-membered substituent was the fastest, while the six-membered substituent of SMZ was the slowest based on the parameters of the kinetic equation. Also, density functional theory (DFT) calculations such as frontier molecular orbitals (FMOs), and molecular electrostatic potential map analysis were performed. It was evidenced that different substituents in SAs can affect the molecular orbital distribution and their stability, which led to the differences in the growth rate of strain YL1 and the degradation rate of SAs. Furthermore, the toxicity of P. ureafaciens is one of the crucial factors affecting the biodegradation rate: the more toxic the substrate and the degradation product are, the slower the microorganism grows. This study provides a theoretical basis for effective bioremediation using microorganisms in SAs-contaminated environments.

Anammox process for aquaculture wastewater treatment: operational condition, mechanism, and future prospective

Treatment of ammonia- and nitrate-rich wastewater, such as that generated in the aquaculture industry, is important to prevent environmental pollution. The anaerobic ammonium oxidation (anammox) process has been reported as a great alternative in reducing ammoniacal nitrogen concentration in aquaculture wastewater treatment compared to conventional treatment systems. This paper will highlight the impact of the anammox process on aquaculture wastewater, particularly in the regulation of ammonia and nitrogen compounds. The state of the art for anammox treatment systems is discussed in comparison to other available treatment methods. While the anammox process is viable for the treatment of aquaculture wastewater, the efficiency of nitrogen removal could be further improved through the proper use of anammox bacteria, operating conditions, and microbial diversity. In conclusion, a new model of the anammox process is proposed in this review.

Construction and comparison of synthetic microbial consortium system (SMCs) by non-living or living materials immobilization and application in acetochlor degradation

The microbial degradation of pesticides by pure or mixed microbial cultures has been thoroughly explored, however, they are still difficult to apply in real environmental remediation. Here, we constructed a synthetic microbial consortium system (SMCs) through the immobilization technology by non-living or living materials to improve the acetochlor degradation efficiency. Rhodococcus sp. T3-1, Delftia sp. T3-6 and Sphingobium sp. MEA3-1 were isolated for the SMCs construction. The free-floating consortium with the composition ratio of 1:2:2 (Rhodococcus sp. T3-1, Delftia sp. T3-6 and Sphingobium sp. MEA3-1) demonstrated 94.8% degradation of acetochlor, and the accumulation of intermediate metabolite 2-methyl-6-ethylaniline was decreased by 3 times. The immobilized consortium using composite materials showed synergistic effects on the acetochlor degradation with maximum degradation efficiency of 97.81%. In addition, a novel immobilization method with the biofilm of Myxococcus xanthus DK1622 as living materials was proposed. The maximum 96.62% degradation was obtained in non-trophic media. Furthermore, the immobilized SMCs showed significantly enhanced environmental robustness, reusability and stability. The results indicate the promising application of the immobilization methods using composite and living materials in pollutant-contaminated environments.

Synergistic effect of chitosan-based sludge aggregates CS@NGS inoculum accelerated the start-up of biofilm reactor treating aquaculture effluent: Insights into performance, microbial characteristics, and functional genes

The moving bed bioreactor (MBBR) process has drawn more attention as a promising biological wastewater treatment process. Nevertheless, achieving quick start-up and microbial biofilm formation remains a significant challenge. Consequently, the present study investigated a novel chitosan-based natural sludge (CS@NGS) seeding strategy for the accelerated start-up of MBBR. Three identical bioreactors were employed; the first bioreactor was without sludge seed as the control (BR1), the second was inoculated only with sludge (BR2), and the third was inoculated with CS@NGS according to the proposed seeding method (BR3). All bioreactors were utilised to treat simulated recirculating aquaculture systems (RAS) effluent. Resultantly, the CS@NGS shortened the start-up period from over twenty to seven days due to the enhanced initial microbial adhesion and biofilm formation. Under optimal conditions, the ammonium removal in BR3 approached 100%, which was relatively higher than BR2 (96.35 ± 1.12%) and BR1 (92.56 ± 2.17%). Moreover, a low nitrite accumulation was exhibited in the effluents, approximately ≤0.03 mg L^-1. The process performance correlated positively with core bacteria from the genera Nakamurella, Hyphomicrobium, Nitrospira, Paenarthrobacter, Rhodococcus, and Stenotrophobacter. The quantitative polymerase chain reaction (qPCR) results demonstrated that the CS@NGS enhanced the expressions of amoA, nxrB, nirK, nirS, narG, and napA nitrogen metabolism-related functional genes to varying degrees. The present study findings can assist the rapid start-up of aquaculture biofilters utilised to solve high nitrite and ammonia accumulation in recirculated water from industrial RAS.

Enhanced denitrification of sewage via bio-microcapsules embedding heterotrophic nitrification-aerobic denitrification bacteria Acinetobacter pittii SY9 and corn cob

In this work, bio-microcapsules were prepared by embedding heterotrophic nitrification and aerobic denitrification (HN-AD) bacteria (Acinetobacter Pittii SY9) and corn cob. Bio-microcapsules (20 g/L of corn cob and 30% v/v suspension of strain SY9) were porous (pore size 2579.74-3725.44 nm; porosity 53.6%-79.9%). Under the appropriate conditions (C/N > 2, temperature of 20-35 ℃, rotation speed of 100-120 rpm, pH of 7-9), TN removal efficiency of bio-microcapsules reached 94.4%, and 74.0% of nitrogen was converted into N₂. The results of kinetics fitting indicated that aerobic denitrification was the limiting step during HN-AD process. Bio-microcapsules could slow the carbon release of corn cob for 120 days, which ensuring high HN-AD performance even at low C/N of 2.8. Bio-microcapsule SBR could stably run for 88 days with TN removal efficiency > 90% for synthetic sewage. Bio-microcapsules embedding strain SY9 and corn cob have prospective applications for enhancing denitrification of sewage.

Effects and mechanisms of aged polystyrene microplastics on the photodegradation of sulfamethoxazole in water under simulated sunlight

Pharmaceutical and microplastics (MPs) have been frequently detected in aquatic environment. In this study, the effects of polystyrene MPs (PS MPs) with different aging degrees on the photolysis of sulfamethoxazole (SMX) in simulated sunlit water were investigated. The results showed that the presence of PS MPs inhibited the photodegradation of SMX, and the photodegradation rate (k_obs) of SMX was negatively correlated with the aging degree of PS MPs (R² = 0.998). The aged PS MPs would cause light-screening effect, thereby reducing the photodegradation of SMX in sunlit water. Further, the free radical quenching experiment showed that the mechanism for inhibiting the photolysis of SMX was the reduction of the triplet excited state SMX (³SMX*). According to sample characterization, aging PS MPs formed more unsaturated chromophores and produced organic intermediates that enhanced photon absorption. Additionally, aged PS MPs also decreased the types and yields of degradation products of SMX via product analysis. This study provides an insight into the environmental behaviors of SMX and the photochemical roles of aged MPs in sunlit surface waters.

Enriched microbial communities for ammonium and nitrite removal from recirculating aquaculture systems

The aim of this study was the enrichment of high-performance microbial communities in biofilters for removal of ammonium and nitrite from aquaculture water. Ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were enriched from different environmental water samples. The microbial communities with higher ammonium and nitrite removal activity were selected and adapted to different temperatures [9 °C, 15 °C, room temperature (25 °C), and 30 °C]. The expression of genes involved in nitrification including ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) were measured in temperature-adapted AOB and NOB microbiomes. The microbial species present in the selected microbiomes were identified via 16s rRNA sequencing. The microbial communities containing Nitrosomonas oligotropha and Nitrobacter winogradskyi showed the highest ammonium and nitrite removal activity at all temperatures used for adaptation. Furthermore, the microbial communities do not contain any pathogenic bacteria. They also exhibited the highest expression of AMO and NXR genes. Using the enriched microbial communities, we achieved a 288% and 181% improvement in ammonium and nitrite removal over the commonly used communities in biofilters at 9 °C, respectively. These results suggest that the selected microbiomes allowed for a significant improvement of water quality in a recirculating aquaculture system (RAS).

Effective photocatalytic degradation of sulfamethoxazole using tunable CaCu3Ti4O7 perovskite

Sulfamethoxazole (SMX) is largely prescribed for bacterial infections but raises a major concern over generation of antibiotic-resistant bacteria in the environment. This study employed various perovskite-type photocatalysts, made by two-step synthesis procedures, to remove SMX. The as-synthesized CaCu₃Ti₄O₇ (CCTO) perovskites were characterized by XRD, SEM-EDX, and DLS. Complete degradation (∼99%; k_obs = 0.0279 min^-1) of SMX was recorded under UV-light irradiation for 90 min in the presence of CCTO. SMX removal rate was investigated under various reaction conditions including pH, catalyst dose, electrolyte (NaCl and NaBr). The astonishing rate of SMX removal (k_obs = 0.0614 min^-1) was observed with the addition of 50 mM NaBr electrolytes in the reaction, which might imply that the appearance of halogen reactive species. CCTO-MS particles were aggregated in traces when the electrolytes concentration increases, resulting in reduced rate of SMX. The SMX concentration abatement and the formation of possible intermediates during photocatalytic reaction were analyzed. The upshot of this study reveals that the inexpensive and environmentally benign CCTO perovskite photocatalyst could be applied for the treatments of emerging contaminants in the future.

Biofilm-mediated bioremediation is a powerful tool for the removal of environmental pollutants

Biofilm-mediated bioremediation is an attractive approach for the elimination of environmental pollutants, because of its wide adaptability, biomass, and excellent capacity to absorb, immobilize, or degrade contaminants. Biofilms are assemblages of individual or mixed microbial cells adhering to a living or non-living surface in an aqueous environment. Biofilm-forming microorganisms have excellent survival under exposure to harsh environmental stressors, can compete for nutrients, exhibit greater tolerance to pollutants compared to free-floating planktonic cells, and provide a protective environment for cells. Biofilm communities are thus capable of sorption and metabolization of organic pollutants and heavy metals through a well-controlled expression pattern of genes governed by quorum sensing. The involvement of quorum sensing and chemotaxis in biofilms can enhance the bioremediation kinetics with the help of signaling molecules, the transfer of genetic material, and metabolites. This review provides in-depth knowledge of the process of biofilm formation in microorganisms, their regulatory mechanisms of interaction, and their importance and application as powerful bioremediation agents in the biodegradation of environmental pollutants, including hydrocarbons, pesticides, and heavy metals.

Bibliometric analysis of microbial sulfonamide degradation: Development, hotspots and trend directions

Microbial sulfonamide degradation (MSD) is an efficient and safe treatment in both natural and engineered ecosystems. In order to systematically understand the research status and frontier trends of MSD, this study employed CiteSpace to conduct a bibliometric analysis of data from the Web of Science (WoS) and the China National Knowledge Infrastructure (CNKI) published from 2000 to 2021. During this time, China, Germany, Spain, the United States and Australia played leading roles by producing numerous high impact publications, while the Chinese Academy of Sciences was the leading research institution in this interdisciplinary research category. The Chemosphere was the top journal in terms of the number of citations. MSD research has gradually progressed from basic laboratory-based experiments to more complex environmental microbial communities and finally to deeper research on molecular mechanisms and engineering applications. Although multi-omics and synthetic community are the key techniques in the frontier research, they are also the current challenges in this field. A summary of published articles shows that Proteobacteria, Gammaproteobacteria, Burkholderiales and Alcaligenaceae are the most frequently observed MSD phylum, class, order and family, respectively, while Bacillus, Pseudomonas and Achromobacter are the top three MSD genera. To our knowledge, this study is the first to investigate the development and current challenges of MSD research, put forward future perspective, and form a relatively complete list of sulfonamide-degrading microorganisms for reference.

Effect of sulfamethoxazole on nitrate removal by simultaneous heterotrophic aerobic denitrification

The increase in mariculture activities worldwide has not only led to a rise of nitrogen compounds in the ecosystem but has also intensified the accumulation of antibiotics in both terrestrial and marine environments. This study focused on the effect of typical antibiotics, specifically sulfamethoxazole (SMX) on nitrate removal from mariculture wastewater by aerobic denitrification process; an aerobic denitrification system feeding with 148.2 mg/L COD, 8.59 mg/L nitrate, 0.72 mg/L nitrite, and 4.75 mg/L ammonium was set up. The hydraulic retention time (HRT) was 8 h. As the aerobic bioreactor started up successfully without SMX dosage, an excellent removal of ammonium, nitrite, and nitrate was achieved at 91.35%, 93.33%, and 88.51%, respectively; the corresponding effluent concentrations were 0.41 mg/L, 0.048 mg/L, and 0.96 mg/L. At the influent SMX doses of 0, 1, 5, and 10 mg/L, the COD removal reached 96.91%, 96.27%, 88.69%, and 85.89%, resulting in effluent concentrations of 4.53, 5.45, 17.38, and 20.6 mg/L, respectively. Nitrification was not inhibited by SMX dosage. However, aerobic denitrification was inhibited by 10 mg/L SMX. Proteobacteria was the most abundant phylum, and surprisingly its abundance increased with the increase in SMX concentration. An excellent SMX degradation was noted at initial SMX dosages of 1, 5, and 10 mg/L; the removal rate was 100%,100%, and 99.8%, respectively. The SMX degrading genera Comamonas sp., Acinetobacter sp., and Thauera sp. are of great validity to wastewater engineers because they have demonstrated efficiency in simultaneous heterotrophic aerobic denitrification and antibiotic degradation as well as COD removal. PRACTITIONER POINTS: Nitrification was not inhibited by increase in SMX dosage. An increase in SMX dosage inhibited aerobic denitrification. COD removal was not affected by increased SMX dosage. Comamonas, Acinetobacter, and Thauera had high efficiency in COD removal and SMX degradation.

Performance and mechanism of simultaneous nitrification-denitrification and denitrifying phosphorus removal in long-term moving bed biofilm reactor (MBBR)

The long-term moving bed biofilm reactor (MBBR) with carrier-attached biofilm was successfully operated for simultaneous removal of nitrogen, phosphorus, and COD at various C/N ratios. Results indicated that 99.60%, 63.58%, 78.94%, and 59.64% of NH₄⁺-N, NO₃^--N, TN, and TP were removed at C/N ratio, hydraulic retention time (HRT), and carrier film amount of 5, 40 h, and 1.2 mg·g^-1. Nitrogen balance analysis showed that more than 89% of nitrogen (C/N = 20, 15, 10, 5) was converted to gas products. Extracellular polymeric substances (EPS), electron transport system activity (ETSA), and enzyme activity of biofilm were evaluated. Protein (PN)/polysaccharose (PS) values and ETSA decreased with the decrease of C/N ratios. Metagenomics sequencing further revealed that the prominent phyla for nitrogen and phosphorus removal were identified including Proteobacteria, Acidobacteria, Nitrospirae, and Chloroflexi. Proteobacteriaand Gammaproteobacteria were identified as the dominant denitrifying phosphate accumulating organisms (PAO) at the phylum and class level, respectively.

Effects of various antibiotics on aerobic nitrogen removal and antibiotic degradation performance: Mechanism, degradation pathways, and microbial community evolution

Little information about the selective stress of various antibiotics and how they influence different stages of aerobic nitrogen removal is available. A long-term aerobic nitrogen removal-moving bed biofilm reactor was established by the inoculation of Achromobacter sp. JL9, capable of heterotrophic nitrification and aerobic denitrification, and aerobic activated sludge. The nitrogen removal and antibiotic degradation performances of various antibiotics were then measured. High total nitrogen (91.83% and 91.51%) removal efficiencies were achieved with sulfamethoxazole or no antibiotics, and lower efficiencies were observed with other antibiotics (trimethoprim, teicoplanin, and ciprofloxacin). These results suggest that various antibiotics have different selective inhibitory effects on aerobic nitrogen removal. Additionally, all antibiotics were partly degraded; proposed degradation pathways according to the detected intermediates included ring-opening, S-N bond cleavage, amination, hydroxylation, and methylation. High-throughput sequencing indicated that aerobic denitrifying, recalcitrant pollutant degrading, and antibiotic-resistant bacteria dominate during the community evolution process.

Application oriented bioaugmentation processes: Mechanism, performance improvement and scale-up

Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.

Characteristics of size-segregated aerosols emitted from an aerobic moving bed biofilm reactor at a full-scale wastewater treatment plant

Aerosol emissions from wastewater treatment plants (WWTPs) have been associated with health reverberation but studies about characteristics of size-segregated aerosol particulate matter (PM) are scarce. In this study, the measurement of particulate number size distribution in the range of < 10 µm, and the collection of PM_10-2.5, PM_2.5-1.0 and PM_1.0, were conducted from an aerobic moving bed biofilm reactor (MBBR) at a full-scale WWTP. MBBR aerosols showed a unimodal number size distribution, with the majority of particles (>94%) in the ultrafine size range (<100 nm). For toxic metal(loid)s or potential pathogens, significant differences were found within MBBR aerosols (PM_10-2.5, PM_2.5-1.0, and PM_1.0), and also between MBBR aerosols and wastewater. Both wastewater and ambient air had important source contributions for MBBR aerosols. The compositions of toxic metal(loid)s in PM_1.0, and the populations of potential bacterial or fungal pathogens in PM_10-2.5 and PM_2.5-1.0, were dominated by that from wastewater. Compared to PM_10-2.5 and PM_2.5-1.0, PM_1.0 had the highest aerosolization potential for the toxic metal(loid)s of As, Cd, Co, Cr, Li, Mn, Ni, U, and Zn, and the genera of Acinetobacter, Pseudomonas and Fusarium. Due to the size-segregated specialty, targeted measures should be employed to reduce the health risks. CAPSULE: The compositions of toxic metal(loid)s in PM_1.0, and the populations of potential pathogens in PM_10-2.5 and PM_2.5-1.0, were dominated by that from wastewater.

Enhancement of mariculture wastewater treatment using moving bed biofilm reactors filled with modified biocarriers: Characterisation, process performance and microbial community evaluation

This research investigated two proposed modified biofilm carriers' performances in treating recirculating aquaculture systems (RAS) wastewater under different salinities (12‰, 26‰, and 35‰) for about 92 days. Three moving bed biofilm reactors (MBBRs; R1, R2, and R3) were filled with unmodified novel sponge biocarriers (SB) served as a control, modified novel SB with ferrous oxalate (C₂FeO₄@SB), and modified novel SB with combined ferrous oxalate and activated carbon (C₂FeO₄-AC@SB), respectively. Under the highest saline condition, a significantly higher ammonia removal efficiency of 98.86 ± 0.7% (p ˃ 0.05) was obtained in R3, whereas R2 and R1 yielded 95.18 ± 2.8% and 91.66 ± 1.5%, respectively. Microbial analysis showed that Vibrio, Ruegeria, Formosa, Thalassospira, and Denitromonas were predominant genera, strictly halophilic heterotrophic nitrifying bacteria involved in nitrogen removal. In conclusion, the synergistic effects of novel sponge, C₂FeO₄ and AC accelerated biofilm formations and stability, subsequently enhanced the removal of ammonia from the mariculture RAS wastewater by the C₂FeO₄-AC@SB carriers in R3.