Application of membrane bioreactor for sulfamethazine-contained wastewater treatment

Strategy for improvement of molecular oxygen activation capacity of PPECu by chlorine doping for water decontamination

The activation of molecular oxygen and generation of reactive oxygen species (ROS) play important roles in the efficient removal of contaminants from aqueous ecosystems. Herein, using a simple and rapid solvothermal process, we developed a chlorine-doped phenylethynylcopper (Cl/PPECu) photocatalyst and applied it to visible light degradation of sulfamethazine (SMT) in aqueous media. The Cl/PPECu was optimized to have a 2.52 times higher steady-state concentration of O2•- (3.62 × 10-5 M) and a 28.87 times higher degradation rate constant (0.2252 min-1) for SMT compared to pure PPECu. Further, the effectiveness of Cl/PPECu in treating sulfonamide antibiotics (SAs) in real water systems was verified through an investigation involving natural water bodies, SAs, and ambient sunlight. The energy band structure, DFT calculation and correlation heat map indicated that the addition of chlorine modulated the local electronic structure of PPECu, leading to an improvement in the electron-hole separation, enhanced the O2 activation, and promoted the generation of ROSs. This study not only puts forward innovative ideas for the eco-compatible remediation of environmental pollution using PPECu, but also sheds new light on the activation of oxygen through elemental doping.

Responses of the microbial community and the production of extracellular polymeric substances to sulfamethazine shocks in a novel two-stage biological contact oxidation system

Introduction

The biological contact oxidation reactor is an effective technology for the treatment of antibiotic wastewater, but there has been little research investigating its performance on the sulfamethazine wastewater treatment.

Methods

In this study, a novel two-stage biological contact oxidation reactor was used for the first time to explore the impact of sulfamethazine (SMZ) on the performance, microbial community, extracellular polymeric substances (EPS), and antibiotic-resistant genes (ARGs).

Results

The chemical oxygen demand (COD) and ammonia nitrogen (NH 4 + -N) removal efficiencies kept stable at 86.93% and 83.97% with 0.1-1 mg/L SMZ addition and were inhibited at 3 mg/L SMZ. The presence of SMZ could affect the production and chemical composition of EPS in the biofilm, especially for the pronounced increase in TB-PN yield in response against the threat of SMZ. Metagenomics sequencing demonstrated that SMZ could impact on the microbial community, a high abundance of Candidatus_Promineofilum, unclassified_c__Anaerolineae, and unclassified_c__Betaproteobacteria were positively correlated to SMZ, especially for Candidatus_Promineofilum.

Discussion

Candidatus_Promineofilum not only had the ability of EPS secretion, but also was significantly associated with the primary SMZ resistance genes of sul1 and sul2, which developed resistance against SMZ pressure through the mechanism of targeted gene changes, further provided a useful and easy-implement technology for sulfamethazine wastewater treatment.

Mechanism for biodegradation of sulfamethazine by Bacillus cereus H38

Degradation of sulfonamides (SAs) by microorganisms has become a focus of current research. Sulfamethazine (SMZ) is a type of SA widely used in the livestock and poultry industry. However, understanding the intermediate products, degradation pathways and mechanism of SMZ biodegradation is limited at present. In this study, a SMZ degrading bacterium Bacillus cereus H38, which can use SMZ as its only carbon source, was isolated from farmland soil. The bacterium was gram-positive with rod-shaped cells. The effects of initial SMZ concentration, pH, temperature and amount of inoculation on the biodegradation of SMZ were investigated by a single factor experiment. The results showed that the maximum degradation rate of SMZ was achieved in the environmental conditions at an initial SMZ concentration of 5 mg/L, pH of 7.0, temperature of 25 °C and inoculation amount of 5%. Under these optimum degradation conditions, strain H38 can completely degrade SMZ within 3 days. The effects of intracellular enzymes, extracellular enzymes and periplasmic enzymes on the SMZ degradation process were compared. It was found that intracellular enzymes contributed the most to the biodegradation of SMZ, and the degradation rate approached 70%. Three possible intermediates were identified by LC-MS/MS, and two degradation pathways were proposed. Whole genome sequencing results showed that the genome size of strain H38 was 5,477,631 bp, including 5599 coding sequences (CDSs), and the GC content was 35.21%. In addition, functional annotation of CDSs was performed to analyze the metabolic pathways of nitrogen and sulfur in strain H38 combining genomics and bioinformatics. This study proposes new insights into the mechanism for biodegradation of SAs and will inform future research.

Effects of pharmaceuticals on membrane bioreactor: Review on membrane fouling mechanisms and fouling control strategies

Pharmaceuticals have become contaminants of emerging concern due to their toxicity towards aquatic life and pseudo persistent nature in the environment. Membrane bioreactor (MBR) is one such technology that has the potential to act as a barrier against the release of pharmaceuticals into the environment. Fouling is the deposition of the constituents of the mixed liquor on the membrane surface and it limit the world-wide applicability of MBRs. To remove foulant layer, aggressive chemicals and extra cost consideration in terms of energy are required. Extracellular polymeric substances (EPS) and soluble microbial products (SMP) are recognized as principal foulants. Presence of pharmaceuticals has been found to increase the fouling in MBRs. Fouling aggravates in proportion to the concentration of pharmaceuticals. Pharmaceuticals exert chemical stress in microbes, hence forcing them to secrete more EPS/SMP. Pharmaceuticals alter the composition of the foulants and affect microbial metabolism, thereby inflicting direct/indirect effects on fouling. Pharmaceuticals have been found to increase or decrease the size of sludge flocs, however the exact mechanism that govern the floc size change is yet to be understood. Different techniques such as coupling advanced oxidation processes with MBR, adding activated carbon, bioaugmenting MBR with quorum quenching strains have shown to reduce fouling in MBRs treating pharmaceutical wastewater. These fouling mitigation techniques work on reducing the EPS/SMP concentration, thereby alleviating fouling. The present review provides a comprehensive understanding of the effects induced by pharmaceuticals in the activated sludge characteristics and identifying the fouling mechanism. Furthermore, significant knowledge gaps and recent advances in fouling mitigation strategies are discussed. This review has also made an effort to highlight the positive aspect of the foulant layer in retaining pharmaceuticals and antibiotic resistance genes, thereby suggesting a possible delicate trade-off between the flux decline and enhanced removal of pharmaceuticals.

Microalgal-based removal of contaminants of emerging concern

The presence of contaminants of emerging concern (CECs) in the environment has been recognized as a worldwide concern. In particular, water pollution by CECs is becoming a major global problem, which requires ongoing evaluation of water resources policies at all levels and the use of effective and innovative wastewaters treatment processes for their removal. Microalgae have been increasingly recognized as relevant for wastewater polishing, including CECs removal. These microorganisms are commonly cultivated in suspension. However, the use of planktonic microalgae for wastewater treatment has limitations in terms of microbiological contamination, process effectiveness and sustainability. The use of consortia of microalgae and bacteria represents a significant advance for sustainable wastewater polishing, particularly when the microorganisms are associated as biofilms. These immobilized mixed cultures can overcome the limitations of suspended-microalgae systems and improve the performance of the involved species for CECs removal. In addition, microalgae-bacteria based systems can offer a relevant combined effect for CECs removal and biomass production enhancement. This study reviews the advantages and advances on the use of microalgae for wastewater treatment, highlighting the potential on the use of microalgae-bacteria biofilms for CECs removal and the further biomass valorisation for third-generation biofuel production.

Pyophage cocktail for the biocontrol of membrane fouling and its effect in aerobic microbial biofilm community during the treatment of antibiotics

Membrane bioreactor systems face an inevitable challenge that is biofouling, which not only hinders the operation of the system, but also poses an environmental and medical concern caused by the increased antibiotic resistance in bacterial biofilms. This study investigates the disruption of membrane fouling using bacteriophage cocktail (Pyophage) in an aerobic membrane bioreactor for treatment of wastewater containing high non-lethal concentration of erythromycin, tetracycline and sulfamethoxazole, while also considering the effect of the cocktail on performance. The results indicate that Pyophage cocktail contributes significantly to the decrease (45%) in transmembrane pressure while also suppressing biofilm-producing bacteria compared to the control reactors. It also reconstructed biodegradation mechanism of antibiotics especially increasing the relative abundance of gram-negative bacteria by enhancement the removal rate of erythromycin and sulfamethoxazole from the aerobic system to 99%.

Degradation of azo dyes under visible light with stable MOF based on tetrastyrene imidazole ligand

In the present work, a new 3D metal-organic framework (MOF) has been synthesized and characterized. The MOF exhibits good chemical stability in aqueous solutions with the pH scale ranging from 3 to 11. Interestingly, the MOF shows high catalytic activities for the degradation of azo dyes (MO, CR and CBR) under visible light without H2O2. The Ea values of the MOF for MO, CR and CBR degradation are obtained to be 23.49, 52.68 and 15.19 kJ mol-1, respectively. In addition, the MOF can be reused in the catalytic process without the catalytic activity decreasing obviously.

Contaminants of Emerging Concern Removal in an Effluent of Wastewater Treatment Plant under Biological and Continuous Mode Ultrafiltration Treatment

This work presents a case study of a wastewater treatment plant (WWTP), located in Biscay (Spain), in which the removal of high-occurrence contaminants of emerging concern (CEC) was studied. The existing biological treatment in the WWTP was complemented with a continuous ultrafiltration (c-UF) pilot plant, as a tertiary treatment. Thus, the effect on CEC removal of both treatments could be analyzed globally and after each operation. A total of 39 CEC were monitored, including pharmaceutical products, industrial additives, food additives, herbicides and personal care products. For evaluation of the efficiencies, the removal rates of the biological and of the c-UF treatments, including their variability over a day and a week in relation to the ammonium content, were examined in the influent of the WWTP. In the biological treatment, a wide range of different removal rates was obtained due to the different CEC’s biodegradability and concentration. In UF, lower, but more constant removal rates, were achieved. In addition, the reduction of the general toxicity by the UF treatment in terms of the Microtox® toxicity assay was also evaluated. After UF, all of the samples yielded values of TU50 lower than 1, confirming this result the UF effectiveness for toxicity removal.

Comparative Study of the Oxidative Degradation of Different 4-Aminobenzene Sulfonamides in Aqueous Solution by Sulfite Activation in the Presence of Fe(0), Fe(II), Fe(III) Or Fe(VI)

This study is focused on advanced oxidation technologies (AOTs) using the combined effect of Fe(0–VI)/sulfite systems, that produce mainly SO4•− radicals, to remove different 4-aminobenzene sulfonamides (SAs), namely sulfamethazine, sulfadiazine, sulfamethizole, from aqueous solutions. Results obtained showed that neither sulfite nor iron alone is able to degrade SAs; however, the combined effect depends on the oxidation state of iron species whose effectiveness to activate sulfite to promote the degradation of SAs increased following this order: Fe(III) < Fe(II) < Fe(0) < Fe(VI). Using Fe(VI)/sulfite, the complete removal of SAs was obtained in 5 min largely surpassing the effectiveness of the other three systems. The sulfonamides’ removal percentage was markedly influenced by sulfite concentration and dissolved oxygen, which improved the generation of oxidant radicals. Response surface methodology was applied, and a quadratic polynomial model was obtained, which allowed us to determine the percentage of SAs degradation as a function of both the iron species and sulfite concentrations. The study of the influence of the water matrix on these AOTs revealed an inhibition of SAs’ removal percentage when using ground water. This is probably due to the presence of different anions, such as HCO3−, Cl−, and SO42− in relatively high concentrations. According to the byproducts identified, the proposed degradation pathways include hydroxylation, SO2 extrusion, and different bond-cleavage processes. Cytotoxicity of degradation byproducts, using MTS assay with HEK 293 and J774 cell lines for the first time, did not show an inhibition in cell proliferation, sustaining the safety of the process.

Hospital wastewater treatment by sponge membrane bioreactor coupled with ozonation process

Herein, a sponge membrane bioreactor (Sponge-MBR) combined with ozonation process was performed to remove the antibiotics which frequently existed in the hospital wastewater. Whilst seven antibiotics i.e., norfloxacin, ciprofloxacin, ofloxacin, sulfamethoxazole, erythromycin, tetracycline and trimethoprim were widely used in medications, this integration was applied for the evaluation of treatment performance under different fluxes. As the results, whilst the antibiotics were eliminated about 45-93%, the tetracycline was completely removed (100%) using Sponge-MBR operated at the flux of 10 LMH. For enhancement of antibiotics removal, the ozonation process was introduced to treat the membrane permeate. Overall efficiencies were 97 ± 2% (trimethoprim), 92 ± 4% (norfloxacin), 90 ± 1% (erythromycin), 88 ± 4% (ofloxacin), 83 ± 7 (ciprofloxacin) and 66 ± 1% (sulfamethoxazole). These results demonstrated Sponge-MBR coupled with ozonation could be a prospective technology for the hospital wastewater treatment.

Insights into the Fate and Removal of Antibiotics in Engineered Biological Treatment Systems: A Critical Review

Antibiotics, the most frequently prescribed drugs of modern medicine, are extensively used for both human and veterinary applications. Antibiotics from different wastewater sources (e.g., municipal, hospitals, animal production, and pharmaceutical industries) ultimately are discharged into wastewater treatment plants. Sorption and biodegradation are the two major removal pathways of antibiotics during biological wastewater treatment processes. This review provides the fundamental insights into sorption mechanisms and biodegradation pathways of different classes of antibiotics with diverse physical-chemical attributes. Important factors affecting sorption and biodegradation behavior of antibiotics are also highlighted. Furthermore, this review also sheds light on the critical role of extracellular polymeric substances on antibiotics adsorption and their removal in engineered biological wastewater treatment systems. Despite major advancements, engineered biological wastewater treatment systems are only moderately effective (48-77%) in the removal of antibiotics. In this review, we systematically summarize the behavior and removal of different antibiotics in various biological treatment systems with discussion on their removal efficiency, removal mechanisms, critical bioreactor operating conditions affecting antibiotics removal, and recent innovative advancements. Besides, relevant background information including antibiotics classification, physical-chemical properties, and their occurrence in the environment from different sources is also briefly covered. This review aims to advance our understanding of the fate of various classes of antibiotics in engineered biological wastewater treatment systems and outlines future research directions.

Overview of sulfonamide biodegradation and the relevant pathways and microorganisms

Sulfonamide antibiotics have aroused increasing concerns due to their ability to enhance the resistance of pathogenic bacteria and promote the spread of antibiotic resistance. Biodegradation plays an important role in sulfonamide dissipation in both natural and engineered ecosystems. In this article, we provided an overview of sulfonamide biodegradation in different systems and summarized the relevant sulfonamide-degrading species and metabolic pathways. The removal of sulfonamides depends on a variety of factors, such as the type and initial concentration of sulfonamides, the properties of water or soil, and treatment process. The removal efficiency of sulfonamides by engineered ecosystems can be improved by optimizing their operating conditions. Much higher sulfonamide removal was also observed in upgraded or advanced treatment systems than in conventional activated sludge systems. Ammonia oxidation might promote sulfonamide biodegradation. In addition, sulfonamide-degraders from different bacterial genera have been isolated and classified, but no bioaugmentation practice has been reported. Different pathways have been detected in sulfonamide biodegradation. Further efforts will be necessary to elucidate in-situ degraders and the metabolic pathways and functional genes of sulfonamide biodegradation.

New insights into the treatment of realN,N-dimethylacetamide contaminated wastewater using a membrane bioreactor and its membrane fouling implications

Treatment of N,N-dimethylacetamide (DMAC) wastewater is an important step in achieving the sustainable industrial application of DMAC as an organic solvent. This is the first time that treatment of a high concentration of DMAC in real wastewater has been assessed using membrane bioreactor technology. In this study, an anoxic–oxic membrane bioreactor (MBR) was operated over a month to mineralize concentrated DMAC wastewater. Severe membrane fouling occurred during the short-term operation of the MBR as the membrane flux decreased from 11.52 to 5.28 L (m² h)⁻¹. The membrane fouling was aggravated by the increased amount of protein fractions present in the MBR mixed liquor. Moreover, results from the excitation–emission matrix analysis identified tryptophan and other protein-like related substances as the major membrane-fouling components. Furthermore, analysis of the DMAC degradation mechanism via high performance liquid chromatography (HPLC) and ion chromatography (IC) revealed that the major degradation products were ammonium and dimethylamine (DMA). Although the MBR system achieved the steady removal of DMAC and chemical oxygen demand (COD) by up to 98% and 80%, respectively at DMAC₀ ≤ 7548 mg L⁻¹, DMA was found to have accumulated in the treated effluent. Our investigation provides insight into the prospect and challenges of using MBR systems for DMAC wastewater degradation.

Treatment of N,N-dimethylacetamide (DMAC) wastewater is an important step in achieving the sustainable industrial application of DMAC as an organic solvent.