Wastewater Treatment Processes Research Articles

Alginate-like exopolysaccharides extracted from different waste sludges exhibit varying physicochemical and material properties

This study examined the influence of different wastewater treatment processes on the physicochemical properties of Alginate-Like Exopolymers (ALE) extracted from waste sludge. Sludge samples were collected from wastewater treatment plants (WWTPs) processing both combined industrial and domestic wastewater, as well as domestic wastewater alone. Among the processes studied, aerobic granular sludge (AGS) produced the highest ALE yield (352 ± 50 mg/g-VSsludge), significantly exceeding that from membrane bioreactor (170 ± 41 mg/g-VSsludge) and conventional activated sludge (<130 mg/g-VSsludge). AGS-derived ALE also had the highest uronic acid content (224 ± 14.5 mg/g-VSsludge), with mannuronic acids playing a critical role in enhancing hydrogel cohesion and stability. The results showed that the distinct microbial consortium in the AGS system, including the presence of Pseudomonas alcaligenes, was strongly associated with increased ALE production. This establishes a novel link between microbial community composition and ALE yield. These insights are crucial for optimizing resource recovery in AGS systems and underscore the potential of ALE for various industrial applications.

Z-Scheme Enabled 1D/2D Nanocomposite of ZnO Nanorods and Functionalized g-C3 N4 Nanosheets for Sustainable Degradation of Terephthalic Acid.

The urgent need to mitigate water pollution and achieve Sustainable Development Goal 14 (SDG 14)-Life below water, necessitates developing efficient and eco-friendly wastewater treatment technologies. This research addresses this challenge by photocatalytic degradation of terephthalic acid, a precursor for PET bottles using environment-friendly and biocompatible photocatalysts. The 1D/2D nanocomposite comprising zinc oxide (ZnO) nanorods and functionalized graphitic carbon nitride (Zn-TG) nanosheets were synthesized and thoroughly characterized. The nanocomposite effectively mitigated the individual drawbacks of Zn-TG agglomeration and the wide band gap of ZnO as confirmed through zeta potential and Tauc's plot studies, respectively. The synthesized nanocomposite achieved ~100 % degradation within 60 minutes, exhibiting superior kinetics (~2.5 times) compared to pristine samples. The enhanced degradation efficiency was elucidated by efficient charge carrier transfer (~5 times faster) and separation (~2 times improved) as confirmed through electrochemical impedance spectroscopy and time-resolved photoluminescence studies. The proposed Z-scheme pathway provides mechanistic insights. This proposed mechanism is supported by extensive electron paramagnetic resonance (EPR) and scavenger studies. The liquid chromatography-mass spectrometry (LC-MS) analysis confirms the formation of less toxic byproducts for ensuring that the wastewater treatment process is efficient and environmentally friendly. This research helps in developing a highly effective and sustainable wastewater treatment technology.

Associative analysis of sludge microbiota and wastewater degradation efficacy within swine farm sludge systems

Industrial wastewater management is a significant global challenge. Sludge microbiota from swine farms may play a crucial role in enhancing wastewater treatment processes, thereby reducing water pollution from industrial activities. A deeper understanding of this complex community could lead to innovative approaches for improving wastewater treatment methods. Sludge samples were collected from the anaerobic, sedimentation, and thickening tanks of ten swine farms. The microbiota communities were analyzed using 16S rRNA full-length sequencing on the PacBio platform, with subsequent data analysis conducted on the QIIME2 platform utilizing the SILVA database. Compared to anaerobic and thickening tanks, the sedimentation tanks exhibited a unique profile of sludge microbiota, with higher abundances of the phyla Proteobacteria, Bacteroidota, and Caldatribacteriota. Additionally, sludges from farms already utilized in processing industrial water—specifically farms B, G, and J—contained higher concentrations of bacteria (> 20 ng/μL), indicating the robustness of the bacterial load for practical industrial use. Furthermore, sludge from farms with higher alpha diversity, such as E, G, I, and J, exhibited enriched degradation profiles, including the degradation of aromatic compounds, polymers, industrial compounds, toluene, and vanillin. The farms were categorized based on wastewater ammonia nitrogen degradation levels, revealing a clustering effect of the microbiota from the sedimentation tanks in the Principal Coordinates Analysis (PCoA) plot. A higher relative abundance of the families Rhodocyclaceae, AKYH767, and Comamonadaceae, and a lower abundance of the families Anaerolineaceae and Christensenellaceae, were found in groups with high ammonia nitrogen reduction, suggesting potential targets for bioaugmentation strategies. In conclusion, this study underscores the critical role of microbial abundance, composition, and biodiversity in optimizing wastewater treatment and advocates for comprehensive microbiota analysis to identify suitable sludge for industrial applications.

Toxicological and environmental risks of enalapril and their possible transformation products generated under phototransformation reactions

Pharmaceutical active compounds (PACs) in the concentration range of hundreds of ng/L to μg/L have been identified in urban surface water, groundwater, and agricultural land where they cause various health risks. These pollutants are classified as emerging and cannot be efficiently removed by conventional wastewater treatment processes. The use of nano-enabled photocatalysts in the removal of pharmaceuticals in aquatic systems has recently received research attention owing to their enhanced properties and effectiveness. In the current study, toxicological and environmental risks of enalapril (ENL) and their possible transformation products (TPs) generated under phototransformation processes (e.g., photolysis and photocatalysis reactions) were assessed. In photolysis reaction, removal of ENL was incomplete (< 16%), while mineralization degree was negligible. In contrast, total removal of ENL was achieved through the photocatalytic process and its maximum mineralization ratio was 66% by using natural radiation. Proposed transformation pathways during the phototransformation of ENL include hydroxylation and fragmentation reactions generating transformation products (TPs) such as hydroxylated TPs (m/z 393) and enalaprilat (m/z 349). Potential environmental risks for aquatic organisms were not observed in the concentrations of both ENL and enalaprilat contained in surface water. However, the acute and chronic toxicities prediction of TPs such as m/z 409, 363, and 345 showed toxic effects on aquatic organisms. Thus, more studies regarding TPs monitoring for both ENL and PhACs with highest occurrence worldwide are necessary for the creation of a database of the concentrations contained in surface water and groundwater for the assessment of the potential environmental risk for aquatic organisms.

Wastewater Treatment through Sequencing Batch Reactor: Adaptation of a Hydro-cyclone Decanter to Enhance Particle Segregation

Objectives:This study investigates the integration of a hydro-cyclone decanter into Sequencing Batch Reactor (SBR) systems to enhance particle segregation during the decanting phase, aiming to improve removal efficiencies of suspended particles in SBR. Methods:A hydro-cyclone separator was designed for the SBR reactor, optimizing particles separation using centrifugal forces without extensive process modifications. Experiments were conducted to evaluate the performance with synthetic and actual wastewater at different concentrations and flow rates.Results and Discussion:The hydro-cyclone decanter achieved removal efficiencies of up to 32.3% for synthetic wastewater and approximately 73.2% for actual wastewater, demonstrating significant particle segregation capabilities. However, its impact on dissolved pollutants like total nitrogen (T-N) and total phosphorus (T-P) was limited.Conclusion:Integrating a hydro-cyclone decanter in SBR systems significantly enhances particle segregation, particularly for larger particles, while moderately improving COD removal, suggesting its effective use in wastewater treatment processes.

Promotion of Single-Electron Transfer by Low-Coordinated Co Single Atoms to Facilitate Advanced Oxidation Processes in Wastewater Treatment.

Heterogeneous catalysts are fascinating for advanced oxidation processes (AOPs) in wastewater treatment to reduce cost, metal contamination, and pH operation limitations. However, they usually encounter low catalytic efficiency because of the difficult single-electron-transfer (SET) pathway during AOPs. Herein, an efficient heterogeneous catalyst for AOPs is realized through the rational regulation of N coordination around Co single-atom (SA) centers in favor of SET. As guided by calculations, low N coordination enables a high density of electronic states at the Fermi energy level of SA Co to facilitate SET activation of peroxomonosulfate (PMS). A special oxide-compounding method is further applied to decrease the N coordination of SA Co on the carbon carriers from common Co1-N3/4 to the desired Co1-N2. Co1-N2 shows a delightful activity for AOP degradation of various organic pollutants with kinetic rate and turnover frequency values up to 0.862 min-1 and 389 h-1, respectively, greatly outperforming those of Co1-N3/4. It is also superior in a wide pH operation range and has strong resistance to environmental disturbances. Detailed mechanistic investigations confirm the generation of singlet oxygen (1O2) instead of common radical O species from the SET between PMS and Co1-N2, corroborating the calculated results and accounting for the enhanced AOP activity.

Settling model to predict microplastics removal efficiency in wastewater treatments

AbstractMicroplastics (MPs) are plastic particles less than 5 mm and become a good carrier and vectors for contaminants in the environment. Current wastewater treatment technologies, including preliminary treatment, primary treatment, secondary treatment, and tertiary treatment, have a certain removal efficiency for MPs or nano‐scale plastic particles. The settling treatment is employed in several wastewater treatment processes. This work built a settling model based on the Reynolds number, drag coefficient, and settling mechanism to predict the microplastics removal efficiency. Microplastics with larger density difference with wastewater, larger size, and CSF closer to 1 are easily captured and have a higher removal efficiency. The calculated removal efficiency according to density, size distribution, different shapes, and the surface loading rate in the operation of wastewater treatment is in a reasonable removal efficiency range. The removal efficiency increases when the surface loading rate decreases.

Comparative Analysis of Pharmaceutical Persistence in Canadian Wastewater Treatment Plants Utilizing Molecularly Imprinted Polymers and Commercial Solid Phase Extraction Sorbents

In this study, the performances of a synthesized Molecularly Imprinted Polymer (MIP) and a commercial Solid Phase Extraction (SPE) cartridge were compared in terms of the removal efficiency and quantification of pharmaceutical compounds in wastewater samples. Concentration analysis of Emtricitabine, Tenofovir, Naproxen, Diclofenac, Ibuprofen, and Efavirenz was conducted in influent, primary effluent, secondary effluent, and post-chlorination water samples using liquid chromatography-UV detection. Regressions analysis revealed high linearity (R2 values from 0.9980 to 0.9999) for the compounds, alongside recoveries ranging from 90.9% to 100%. The method detection limits (MDLs) were also determined. Removal efficiencies were computed, with Naproxen and Ibuprofen demonstrating complete removal (100%), while other compounds displayed different of removal efficiency levels. The MIP was found to perform slightly better than traditional SPE cartridges in terms of selectivity, efficiency, and overall performance. This study provides valuable insights into the concentrations of target compounds at various treatment stages, emphasizing the importance of choosing extraction cartridges in wastewater treatment processes.

Improvement of Phosphorus Removal from Wastewater Through Fermentation of Low-Concentrated Wastewater Sludge and Increased Production of Volatile Fatty Acids

This article presents the results of a two-stage study: the first stage involved assessing the dependence of the increase or decrease in the concentration of volatile fatty acids (VFAs) on external factors and then assessing the relationship between the VFA concentration in the supernatant after fermentation and the processing characteristics (temperature, mixing mode, alkalinity, pH, nitrogen and phosphorus content). The greatest increase in VFAs (content up to 285 mg/L in the supernatant) was achieved at a temperature in the range of 28 to 38 °C with constant mixing of the sludge. Based on the results of the second stage, a conclusion was made on the efficiency of using a particular substrate depending on the concentration of phosphorus phosphates in the incoming wastewater. The study results showed that 7.54 mg/L of phosphorus can be removed with a given probability (for activated sludge, raw sludge and wastewater). It is recommended to compensate for the excess of this concentration by dosing the acetic acid solution at a rate of 3800 meq/L of VFA per 1 mg/L of phosphorus phosphates. The literature does not contain any results of parallel studies of the operation of a controlled bioreactor with artificial external feeding and acidified VFA. The results of the study can be applied in planning sludge acidification systems in the technological scheme of wastewater treatment and sludge processing.

Removal of contaminants in paper dyeing wastewater by Fenton and photo-Fenton processes with biological treatment

Due to the production of huge quantity of potentially toxic and recalcitrant pollutants, which cannot be completely decomposed with conventional biological wastewater treatment processes, in the paper industry, reliable treatment processes are highly required. This study conducted effective experiments of different series of processes to decompose persistent contaminants in the paper wastewater under controlled conditions of the used processes to meet the effluent quality standards of Korea Ministry of Environment in terms of CODMn (< 130 mg/L). For Biological treatment, Fenton, and photo-Fenton processes, various operational parameters were adjusted to determine the optimal conditions for CODMn value. Due to large quantity of refractory contaminants in the wastewater, single treatment process was not enough to meet the requirement of CODMn. Herein, we achieved the goal with two approaches: (1) secondary Fenton oxidation after biological and primary Fenton treatments, and (2) photo-Fenton treatment after biological treatment alone. The secondary Fenton oxidation process is an additional process operated under the same condition of the primary Fenton treatment to treat the effluent from the primary Fenton treatment. Ultimately, the residual CODMn concentrations of the secondary Fenton and single photo-Fenton treatment were 62.7 and 85.3 mg/L, respectively. However, the secondary Fenton required larger amounts of reagents and produced significant amounts of sludge, which require post-treatment, compared to single photo-Fenton treatment. Therefore, it suggests that the application of photo-Fenton was more efficient than the secondary Fenton in terms of economic feasibility and post-treatment requirement.

Introducing a prediction method for the photodegradation of p-cresol, a phenolic contaminant of emerging concern, in wastewater effluent.

Despite extensive efforts to understand the photodegradation of phenolic contaminants of emerging concern (PhCECs) in aquatic systems, prediction methods, especially in waters containing effluent organic matter (EfOM), remain underdeveloped. This study introduces a prediction method for p-cresol, a representative PhCECs, based on correlations between EfOM optical parameters and p-cresol kinetic parameters. We examined p-cresol photodegradation in various EfOM samples, characterized by their optical properties, and used the reaction rate coefficient between EfOM and p-cresol, α3EfOM⁎, to quantify and predict p-cresol degradation in different wastewater effluent samples. Results showed significant correlations between p-cresol's photodegradation rate constant (0.144 to 0.441 h-1) and EfOM characteristics, with α3EfOM⁎ values ranging from 4 × 1011 to 10 × 1011 M-1 s-1. The method was validated with p-cresol at concentrations ranging from 25 to 100 μM and multiple EfOM samples. The method's applicability was further evaluated using propranolol, a pharmaceutical contaminant of emerging concern, demonstrating its versatility for predicting the degradation behavior of other contaminants in different wastewater samples. The method accurately predicted p-cresol and propranolol degradation across diverse wastewater samples, suggesting its potential for expansion to other classes of contaminants, aiding in water quality management, improving wastewater treatment processes, and enhancing environmental risk assessments.

Potensi Batang Pisang sebagai Media Filter pada Pengolahan Air Limbah Laundry

Banana stems have the potential to be used as filter media in the laundry wastewater treatment process. Laundry wastewater will contain hazardous substances that have the potential to pollute the environment if it is not treated adequately before disposal. Considering the fact that banana stems have a high hygroscopic capacity and cellulose content which is capable of absorbing inorganic chemicals, the use of banana stems as a filter media is considered a realistic option. The research method used is the filtration reactor method, and there are differences in the amount of time invested and the thickness of the banana stem, which can range from 20 to 40 centimeters. There were differences in the decrease in the parameter values of pH, COD, TSS, phosphate, and MBAS with variations in the thickness of the banana stem media. The largest decrease in pH observed occurred at a media thickness of 40 centimeters. Based on the research results, it was found that there was variation in the extent to which parameters were reduced overall. A one-day soak is the most effective way to reduce the severity of these properties. In addition, research findings show that banana stems are not effective enough in processing laundry wastewater.

Photocatalysis coupled electro-Fenton process for treatment of acrylamide wastewater: an optimised study

ABSTRACT Electro-Fenton is a commonly used approach for pollutant removal from different wastewater that requires high energy consumption. Coupling electro-Fenton with solar energy could potentially overcome high power consumption. Thus, this study combined photocatalysis with three-dimensional electro-Fenton to treat acrylamide (AM) wastewater. The removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH3−N), and total organic carbon (TOC) in photocatalysis-coupled electro-Fenton were studied. The effects of current density, iron powder dosage, plate spacing, and photocatalyst dosage on COD and NH3−N removal were also optimised using response surface methodology (RSM). The photocatalysis coupled three-dimensional electro-Fenton reduced energy consumption compared to single photocatalysis or electro-Fenton technology. The COD and NH3−N removal rates were 82.444% and 92.810%, respectively, at the current density of 16.000 mA/cm2, iron powder dosage of 1.330 g, plate spacing of 16.643 mm, photocatalyst dosage of 0.2 g. This study demonstrated that organic pollutants can be degraded efficiently at a low concentration of catalysts coupled with the electro-Fenton process, offering a low-energy consumption treatment of wastewater.

Simultaneous degradation of pharmaceuticals and personal care products in hospital wastewater using ozone under ultraviolet irradiation

The discharge of Pharmaceuticals and personal care products (PPCPs) from industries and hospitals are responsible for the contamination of water body with slow or non-degradable toxic compounds. The removal of these contaminants required advanced treatment process because of unable to treat by conventional wastewater treatment process. In this study, the degradation of PPCP compounds, including caffeine (CAF), atenolol (ATL), carbamazepine (CBZ), sulfamethoxazole (SMX), trimethoprim (TMP), and acetaminophen (ACT) was evaluated under exposure to 1.0 and 1.5 mg/L dissolved ozone (O3), both with and without ultraviolet (UV) irradiation (254 nm). Using liquid chromatography with tandem mass spectrometry, we determined that the removal efficiency for the targeted contaminants exceeded 95 % within just 20 min of exposure to both 1.0 and 1.5 mg/L O3. However, when treated with UV light alone, the removal efficiency was limited at 3 %–11 %. A combination treatment involving dissolved 1.5 mg/L O3 and UV light led to over 97 % removal within 7 min. This outcome was attributed to hydroxylation reactions, aromatic ring opening, oxidation, and mineralization facilitated by the HO and peroxide generated through the photolysis of O3. The degradation rate of PPCP compounds followed pseudo-first-order kinetics and showed a decrease in the presence of humic acid and hospital wastewater further decreased it. Moreover, O3/UV treatment generated lower-weight degradation products. The toxicity analysis revealed that these transformation products exhibited environmental benignity and minimal health risks which O3/UV treatment potentially minimizes the presence of harmful byproducts. These findings provide a foundation for developing combined hybrid systems for PPCP containing wastewater, containing membrane filtration with ozonation system.

Comparative analysis and application of soft sensor models in domestic wastewater treatment for advancing sustainability

ABSTRACT This study focuses on the development and evaluation of soft sensor models for predicting NH3-N values in a wastewater treatment process. The study compares the performance of linear regression (LR), neural networks (NN) and random forest regression (RFR) models. The proposed methodology involves optimizing the sequencing batch reactor process using artificial intelligence and an automatic control system. Real-time NH3-N values are obtained by inputting data from electronic conductivity and temperature sensors into the prediction models. Once the predicted NH3-N value falls below the effluent standard, the cycle ends, improving energy efficiency and sustainability by cutting down the agitator and aerator. The research results demonstrate that the RNN-based NH3-N soft sensor built in this study exhibits the best performance, which is promising for wastewater treatment process optimization and evaluation. The results show that sensor model NNR[0.5Y]H exhibits exceptional performance, utilizing recurrent neural network with 5-step input delays. Sensor NNR[0.5Y]H exhibits an R2 of 0.921, an RMSE of 6.110, and an MAE of 4.558. Based on the findings, recurrent neural network (RNN) variants emerge as the most effective modeling technique due to their ability to capture temporal dependencies and handle variable-length sequences. This study provides satisfied performance results for the NNR[0.5Y]H soft sensor model in NH3-N monitoring and process optimization in wastewater treatment, highlighting the effectiveness of recurrent neural networks and their contribution to improving interpretability, accuracy, and adaptability of soft sensor models.

Preparation of Microelectrolysis Filler Using Coal Slag for the Removal of Hazardous Substances in Contaminated Water.

Presently, the utilization of gasification slag in the context of wastewater treatment is constrained. Furthermore, the presence of dye wastewater and wastewater containing hazardous metals represents a significant threat to human health. Accordingly, the present study prepared a microelectrolytic filler (MF) from gasification slag via a high-temperature roasting method and evaluated its degradation performance in water containing organic matter and harmful metal ions. The impact of varying preparation conditions, including initial solution pH and MF dose, on the degradation process was examined. The removal of methyl blue was found to be 92.21% at an initial pH of 2, a reaction time of 300 min and a dosage of 40 g L-1. The removal of Cu(II), Cd(II), and Pb(II) metal ions was 97.32, 96.58, and 99.38%, respectively, at an initial pH of 4, a reaction time of 180 min, and a dosage of 10 g L-1. Following five cycles, the MF process demonstrated continued efficacy in the removal of dyes and heavy metals from the wastewater. A mechanistic analysis revealed that the water treatment process is not a single adsorption process. Instead, it was found that organic macromolecules undergo chain-breaking reactions, while heavy metal ions undergo redox reactions. The wastewater treatment process comprises a number of distinct strategies, including electrochemical reactions, adsorption, flocculation, and precipitation. These findings illustrate the potential of a gasification slag green recycling approach to treat waste with waste, in alignment with the principles of sustainable development.

Chromium speciation from tannery wastewater using spectroscopic techniques

The toxicity and reactivity of chromium (Cr) depend on its chemical form or oxidation state which directs the significance of chromium speciation. Cr(VI) is a ‘Class A’ carcinogen whereas Cr(III)) is considered as essential for metabolism. In this work, concentrations of Cr species in different sampling sites of a tannery effluent have been spectroscopically determined. Cr(VI) was determined by UV-visible spectrophotometer through azo dye formation. Total Cr was determined by FAAS while Cr(III) was through subtraction. The Cr(IV) concentration before and after treatment was found in close proximity since the wastewater treatment process was evidently not effective at reducing the level of Cr(IV) in the waste stream (i.e., 3.34 mg/ L versus 3.15 mg/L). The Cr(VI) concentration after treatment (3.15 mg/L) is more than 31 times higher than the permissible limit of WHO (0.1 mg/L). Furthermore, the concentration of Cr(VI) in the downstream of the receiving river (0.59 mg/L) is more than 12 times higher than the upstream (0.046 mg/L) while Cr(III) in the downstream (25.73 mg/L) is more than 50 times higher than the upstream concentration (0.51 mg/L), confirming that the pollution of the river is from the tannery effluent.

Sustainability Strategies in Municipal Wastewater Treatment

The European Parliament adopted a legislative resolution of 10 April 2024 on the proposal for a directive of the European Parliament and of the Council concerning urban wastewater treatment. The reduction in pollution in discharged treated wastewater in the parameters of BOD5, total nitrogen, and total phosphorus was emphasized. Based on these results, it stated that the impacts on the quality of lakes, rivers, and seas in the EU are visible and tangible. At the same time, it was emphasized that the sector of urban wastewater removal and treatment is responsible for 0.8% of total electricity consumption and about 0.86% of all greenhouse gas emissions in the entire EU. Almost a third of these emissions could be prevented by improving the treatment process, better use of sewage sludge, and increasing energy efficiency, as well as a higher rate of use of renewable resource technologies. It is also necessary to integrate treatment processes into the circular economy. Sludge management and water reuse are suboptimal as too many valuable resources are still being wasted. This article focuses on sustainable municipal wastewater treatment, innovative and new wastewater treatment processes and technologies (combined and hybrid processes, ANAMMOX, etc.) and their use in practice with the aim of increasing environmental and energy efficiency and reducing the carbon footprint. The research is focused on the possibilities of increasing the efficiency of energy processing of sludge, reuse of nitrogen and phosphorus, sludge, and reuse of treated wastewater.

Enhanced methylene blue degradation and miniralization through activated persulfate coupled with magnetic field

In this work, for the first time, the effectiveness of the degradation and mineralization process of methylene blue) MB) was investigated using activated persulfate (PS) with a magnetic field. The effect of various operating parameters, including pH, PS (5–20 mg/L), intensity of the magnetic field (1–4 A), initial concentration of methylene blue dye (25–100 mg/L), and contact time (30–120 min), was evaluated. Process optimization was conducted via the Taguchi model, and the optimal values of these factors were found to be pH = 5, PS = 10 mg/L, MFs = 4 A, reaction time = 30 min, and the initial concentration of methylene blue dye = 50 mg/L. Under optimal conditions, the methylene blue removal efficiency and TOC destruction efficiency reached 91.8% and 88%, respectively. The kinetics of the process followed pseudo-second order (R2 = 0.9723). According to the promising results of the research, the efficiency of dye purification using a magnetic field has increased by about three times compared to the state without this factor. It can be suggested that this system be used as a wastewater treatment process for the textile industry to reduce the toxicity of wastewater and total organic carbon (TOC).

Exploring the effects of polyethylene and polyester microplastics on biofilm formation, membrane Fouling, and microbial communities in Modified Ludzack-Ettinger-Reciprocation membrane bioreactors

Microplastics (MPs) inevitably enter wastewater treatment plants (WWTPs), yet their impacts remain poorly understood. This study investigates the effects of MPs on system performance and membrane fouling in a Modified Ludzack-Ettinger (MLE)-Reciprocation Membrane Bioreactor (rMBR), an energy-efficient alternative to conventional membrane bioreactors. Additionally, the study examines changes in microbial community induced by different types and shapes of MPs—polyethylene (PE) pellets and polyester (PES) fibers— as well as biofilm formation on MPs, using next-generation sequencing. Results revealed that transmembrane pressure (TMP) increased 2–3 times faster in the presence of PE pellets, while TMP remained stable during the PES stage, implying that MP type and shape could influence biofouling behaviors. Furthermore, enhanced nitrate removal was observed in the aerobic tank due to denitrifying biofilm formation on MPs. However, PES MPs reduced nitrate removal efficiency from 99.6 ± 0.3 % to 90.9 ± 7.9 % and decreased the relative abundance of denitrifying bacteria. Numerous taxa showed affinity to PE pellets, including some pathogens, e.g., Norcadia and Mycobacterium. Notably, an uncultured phylum Candidatus Saccharibacteria dominated in membrane biofilm and MPs, reaching up to 37 % relative abundance. This study is the first to explore how different types and shapes of MPs affect membrane bioreactor systems, particularly with respect to microbial community structure and biofilm formation. The findings offer new insights into the influence of MPs on wastewater treatment processes and highlight the significance of the uncultured phylumCandidatus Saccharibacteriain membrane fouling.