Search Results (131)

Effective management of wastewater treatment plants often requires real-time measurements of Biochemical Oxygen Demand (BOD). Conventional methods for determining Biochemical Oxygen Demand (BOD) are often time-consuming, labor-intensive and prone to inaccuracies. Microbial Fuel Cells (MFCs) have emerged as a viable alternative technology for BOD measurement, offering real-time monitoring capability. However, challenges remain in its validity for testing different types of wastewater. This study developed a cost-effective dual-chamber MFC with graphite felt electrodes and a CMI-7000 membrane, inoculated with a microbial consortia grown from anaerobic sludge at optimal conditions (35 °C, pH 7, 1000 Ω external resistance). After one month of biofilm formation, the MFC produced 600 mV. Voltage outputs were measured at six BOD₅ concentrations (36 to 583 mg/L) in synthetic wastewater, showing a strong linear correlation between BOD₅ concentrations and voltage outputs. The MFC was also tested with five domestic wastewater samples with BOD₅ values ranging between 81 and 405 mg/L. The output voltages were inserted into the derived voltage–BOD correlation to obtain BOD₅ values within 2.5% to 11% of conventional laboratory results. These findings confirm the potential of MFC-based biosensors as an efficient and accurate tool for real-time wastewater monitoring. Full article

In recent years, the simultaneous partial nitrification, anammox, and denitrification (SNAD) process has attracted considerable attention due to its advantages such as low energy consumption and low sludge production. This study investigated the long-term performance and microbial mechanisms of a single-stage moving bed biofilm reactor (MBBR) employing the SNAD process for treating real domestic sewage at room temperature. A pre-carbon adsorption unit (reactor A) reduced the influent C/N ratio from 5.68:1 to 3.13:1, enabling efficient nitrogen removal in reactor B. Results demonstrated that dissolved oxygen (DO) and C/N ratio critically influenced system performance. At DO ~0.3 mg/L, stable SNAD operation achieved 65% total nitrogen (TN) removal, with synergistic contributions from partial nitrification, anammox, and heterotrophic denitrification. Elevated C/N ratios (4.71:1) reduced TN removal by ~30%, linked to decreased abundances of anammox bacteria. Microbial analysis revealed Candidatus Brocadia as key anammox bacteria, Nitrospirae as dominant ammonia-oxidizing bacteria and Denitratisoma as main denitrifying bacteria to drive nitrogen conversion. This study confirms the feasibility of SNAD-MBBR for real domestic sewage under ambient conditions, highlighting optimal DO and C/N control for microbial synergy and process stability. Full article

Increasing domestic sewage production associated with urban population growth poses environmental challenges. Biosolids from wastewater treatment can recycle nutrients in agriculture, while plant growth-promoting rhizobacteria (PGPR) enhance nutrient availability and plant performance. This study evaluated the effects of the combined application of sewage sludge–derived biosolid and Bacillus aryabhattai on sunflower growth, biomass production, physiological traits, and nutrient status during the early growth stage under greenhouse conditions. We hypothesized that this combined treatment would enhance plant performance compared with biosolid application alone. Four treatments were established: control (T1), 5 g of biosolid alone (T2), 5 g biosolid + 3.2 mL B. aryabhattai (T3), and 5 g biosolid + 6.4 mL B. aryabhattai (T4). The formulation contains B. aryabhattai strain CMAA 1363 (1 × 10⁸ CFU mL⁻¹) as the active microbial component, together with humic substances and other formulation agents (thickener, preservative, and water). The Plants were grown for 44 days. The data were analyzed using one-way ANOVA followed by mean comparison among treatments. Shoot dry mass was significantly higher in T4 compared with the T1 and T2 (p < 0.001), while no significant difference was observed between T3 and T4 (p > 0.05). Biosolid application increased the photosynthetic rate, and its combination with B. aryabhattai further enhanced photosynthetic performance, with significant difference detected between bacterial doses only at the end of growth period. Substomatal CO₂ concentration was lower in inoculated treatments, indicating greater CO₂ assimilation efficiency. Total chlorophyll increased with the addition of sludge and further increased by inoculation with 6.4 mL. Leaf N, Mn, and Zn contents were highest in T4. Overall, the combined application of biosolid and B. aryabhattai improved photosynthetic efficiency and biomass accumulation, highlighting the potential of integrating biosolids and beneficial rhizobacteria as a sustainable approach for nutrient recycling and improved crop productivity in agricultural systems. Full article

The rapid growth of synthetic textile production has intensified the release of micro- and nanoplastics (MPs/NPs) into aquatic environments, primarily through industrial effluents and domestic laundering. Textile-derived microplastics, especially polyester fibers and polymeric coating fragments, constitute a significant fraction of plastic contamination in wastewater systems. Although wastewater treatment plants (WWTPs) can remove a large proportion of MPs, substantial quantities accumulate in sewage sludge, raising concerns about long-term environmental persistence and secondary release pathways. This review critically examines the sources, classification, and release mechanisms of textile-based micro- and nanoplastics, including fibrous debris and coating-derived fragments. Then it focuses on current identification and removal technologies, such as sedimentation, coagulation/flocculation, electrocoagulation, flotation, membrane filtration, adsorption, and biodegradation, and on the emerging strategy of converting recovered microplastics into value-added porous carbon materials via hydrothermal treatment and pyrolysis. Carbonized microplastics exhibit high surface area and adsorption capacity for dyes, heavy metals, and organic pollutants, offering a circular approach that simultaneously mitigates plastic pollution and enhances wastewater treatment efficiency. By integrating source control, optimized removal technologies, and carbonization-based valorization, this review proposes a dual-benefit framework that transforms textile-derived microplastic waste from an environmental liability into a functional resource for sustainable water purification. Full article

Microplastics (MPs) persist in wastewater treatment systems owing to their durability and mobility. As critical interception points, wastewater treatment plants (WWTPs) receive MPs from diverse domestic and industrial sources. This review synthesizes peer-reviewed studies (2009–2026) to evaluate MP mass flux, in-plant transformation, and elimination across primary, secondary, and tertiary stages. While conventional processes typically remove 60–90% of MPs, advanced tertiary technologies, such as membrane bioreactors and rapid sand filtration, can achieve efficiencies exceeding 95%. The fate of MPs is governed by density-driven settling and biological aggregation; however, the significant accumulation of MPs in sewage sludge represents a critical pathway for environmental re-entry. This review highlights key knowledge gaps, including inconsistent analytical methodologies, evidence of in-plant fragmentation generating nanoplastics (NPs), and uncertainties regarding full-scale mass flows. Furthermore, the review synthesizes mass flux data to clarify the partitioning of MPs between the effluent and sludge, identifying biosolids as a primary sink. The review concludes by proposing a transition from physical separation to elimination technologies (e.g., AOPs), alongside standardized monitoring and regulatory frameworks, to achieve sustainable reductions in MP emissions. Full article

Wastewater treatment systems retain a significant proportion of microplastics (MPs) derived from domestic and industrial discharges; however, these emerging pollutants are not completely removed and tend to accumulate in the biological sludge generated during the treatment process. In this study, three biological-type wastewater treatment plants (WWTPs) located in Acapulco, Mexico, were analyzed. The concentrations of MPs in the biological sludge ranged from 830 to 9300 particles/L. Using differential scanning calorimetry (DSC), the predominant polymers identified were high-density polyethylene (HDPE), polyethylene terephthalate (PET), and polypropylene (PP). It was estimated that the monthly concentrations of MPs in the sludge could reach up to 5.36 × 10⁹ particles/L, while the annual concentrations could rise to 3.55 × 10¹⁰ particles/L. These findings highlight the urgent need to review and update the regulatory framework related to the use of residual sludge for agricultural purposes, since high loads of MPs and their transfer pose a potential risk to soil quality, ecosystem health, and long-term environmental sustainability. Full article

In this study, we investigated the impact of varying iron (Fe) and aluminum (Al) contents on the adsorption of phosphonates to activated sludge. Phosphonates originating from household applications account for up to 40% of the non-reactive dissolved phosphorus in domestic sewage treatment plants and thus can contribute to the eutrophication of water bodies. Although these substances are not readily degradable, substantial quantities, ranging from 40% to more than 90%, are removed by sludge adsorption. The results demonstrate a strong correlation between the adsorption of aminophosphonates and the Fe³⁺ content of the sludge. The maximum phosphonate loadings were 5.94 mmol g⁻¹ Fe³⁺ for ATMP, 4.94 mmol g⁻¹ Fe³⁺ for EDTMP, 4.74 mmol g⁻¹ Fe³⁺ for DTPMP, and 2.25 mmol g⁻¹ Fe³⁺ for glyphosate. In contrast to pure ferric hydride flocs, the adsorption of phosphonates was approximately threefold higher when the hydroxides were located within activated sludge flocs. It is concluded that native sludge flocs provide larger iron surfaces than ferric hydroxide alone. Based on the weight of the adsorbents, aluminum salts were four times less efficient than ferric salts. In sludge without ferric or aluminum hydroxides, phosphonate adsorption was negligible. Full article

The study investigates the performance of polyethersulfone (PES) ultrafiltration (UF) membranes modified with a coating of polymerizable bicontinuous microemulsion (PBM) for membrane bioreactor (MBR) applications. Two types of PBM-modified PES membranes—casting-coated and spray-coated—were compared with a commercial PES membrane. A laboratory side-stream MBR (ssMBR) was employed to treat model wastewater (MW) with activated sludge under aerobic conditions. The fouling propensity of the membranes in ssMBR was evaluated through the implementation of two protocols: (i) flux-step test to treat low-strength domestic model wastewater (DMW) and (ii) constant flux test to treat high-strength olive mill model wastewater (OMW). The findings indicated that both the commercial PES and PBM spray-coated PES membranes started to critically foul at 36 L m⁻² h⁻¹. The PBM spray-coated membranes showed enhanced fouling resistance in comparison to the PBM casting-coated membranes. The deposition of the biofouling layer was the thinnest on PBM spray-coated membranes, which can be attributed to the low surface charge and high hydrophilicity of the modified membrane surface. In contrast, deposition of a thicker fouling layer was found on the commercial PES membrane, which can be attributed to the relatively higher surface charge promoting organic adsorption. A comparison of the fouling trends exhibited by commercial PES and PBM spray-coated membranes in OMW treatment revealed that they have similar fouling tendencies. However, a notable distinction emerged when the PBM spray-coated membrane was observed to demonstrate a lower fouling propensity accompanied by comparatively thinner fouling layers. The results demonstrate that the PBM spray-coated membranes have enhanced fouling resistance and filtration efficacy in MBRs treating wastewater with diverse strengths, thereby affirming their potential for application in wastewater treatment systems. Full article

Advanced control systems have been recently implemented in wastewater treatment plants (WWTPs) to optimize activated sludge processes, reduce operational costs, and decrease energy consumption, with the aim of moving toward sustainable operation. Real-time dynamic control of NH₄⁺-N and NO₃⁻-N concentrations is important for the optimization of biological nitrogen removal (BNR) processes. This study presents an advanced control strategy based on continuous monitoring of NH₄⁺-N and NO₃⁻-N concentrations at 22.8–25.1 °C to enhance nitrogen removal performance. Specifically, the control performance of an intermittently aerated and fed activated sludge (IAF-AS) system treated with domestic wastewater was evaluated using a controller under two different scenarios: (i) normal conditions at constant ammonium nitrogen loading rate (ALR) and (ii) varied conditions with a sudden increase in ALR. The effect of temperature changes on BNR efficiency was not analyzed. In both scenarios, the optimal duration ratio of the nitrification and denitrification phases was determined, which depended on the ALR. In the first scenario, at a constant ALR of 0.2 g L⁻¹ d⁻¹, the controller kept the duration of nitrification and denitrification at a low level, succeeding in complete nitrogen removal in less than 60 min. In the second scenario, when the ALR exceeded 0.3 g L⁻¹ d⁻¹, the controller dynamically extended these phases to achieve the effluent endpoints of 2 mg L⁻¹ NH₄⁺-N and 1 mg L⁻¹ NO₃⁻-N. The results show that the use of real-time dynamic control is of great importance, as the nitrogen removal efficiency is maximized by minimizing the anoxic/aerobic duration ratio, thus significantly reducing the aeration energy requirement and operating cost. Full article

Linear alkylbenzene sulfonates (LAS) are one of the organic pollutants of most concern in sewage sludge due to their widespread occurrence in domestic sewage. In this work, the occurrence of LAS was assessed in 15 wastewater treatment plants (WWTPs), with different sludge stabilization treatments, from September 2023 to March 2024. Samples were analyzed by ultrasound-assisted extraction and LC-MS/MS. In primary sludge, LAS homologues displayed the typical fingerprint of laundry detergents, suggesting these products are a primary source in influent wastewater. There was no clear correlation between the population served and the LAS concentrations in the studied WWTPs. The highest concentrations of LAS (sum of the homologues C10–C13) were found in anaerobic lagoons, followed by aerobically (6438 mg/kg) and anaerobically digested (5521 mg/kg) sludge. The lower levels were observed in composted sludge (215 mg/kg). 100% of the composted samples showed concentrations lower than 2600 mg/kg (concentration limit currently proposed by the EU for LAS), while these percentages were reduced to 25 and 13% in the case of aerobically and anaerobically digested sludges. These results showed that composting could be an effective method for ensuring compliance with a future EU Directive on sludge application to the soil. Full article

High-molecular-weight polycyclic aromatic hydrocarbons (PAHs), such as pyrene, are persistent environmental pollutants that threaten soil health and agricultural productivity due to their resistance to degradation. This study evaluated the efficacy of domesticated bacteria isolated from contaminated farmland soil and activated sludge, used alone and in combination with corn (Zea mays L.), to remove pyrene from soil, enhance plant growth, improve tolerance, and ensure crop safety. Six bacterial strains were isolated: three from polluted farmland soil (WB1, WB2, and WF2) and three from activated sludge (WNB, WNC, and WH2). High-throughput 16S rRNA amplicon sequencing profiled bacterial communities after 30 days of treatment. Analytical tools, including LEfSe, random forest, and ZiPi analyses, identified biomarkers and core bacteria associated with pyrene degradation, assessing their correlations with plant growth, tolerance, and pyrene accumulation in corn straw. Bacteria from activated sludge (WNB, WNC, and WH2) outperformed farmland soil-derived strains and the inoculant strain ETN19, with WH2 and WNC achieving 65.06% and 87.69% pyrene degradation by days 15 and 30, respectively. The corn–bacteria consortium achieved up to 97% degradation. Activated sewage sludge (ASS)-derived bacteria were more effective at degrading pyrene and enhancing microbial activity, while soil-derived bacteria better promoted plant growth and reduced pyrene accumulation in straw. Microbial communities, dominated by Proteobacteria, exhibited high species richness and resilience, contributing to xenobiotic degradation. The corn-domesticated bacteria consortia effectively degraded pyrene, promoted plant growth, and minimized pollutant accumulation in crops. This remediation technology offers a promising strategy for rapid and sustainable bioremediation of agricultural soils contaminated with organic compounds such as PAHs or other complex pollutants, while promoting the development of efficient bacterial communities that enhance crop growth. Full article

Sludge bulking in wastewater treatment is often caused by massive filamentous bacteria. This study aimed to turn such bacteria into a stable system dominated by filamentous biofilms (FBs) by using a continuous flow reactor (CFR) fed with simulated domestic wastewater; to address FBs’ poor solid–liquid separation and uncontrollable sludge retention time (SRT), string carriers were added, SRT was controlled at 30 days, and parameters like mixed liquid suspended solids (MLSS) and sludge volume index (SVI) were monitored. Results showed filamentous Sphaerotilus (68–93% of FBs) self-aggregated as FBs’ reticular skeleton (loose, porous, stable, max 8 cm) with non-filamentous bacteria anchoring; FBs achieved >80% COD/NH₄⁺-N removal despite low MLSS (<1000 mg/L) and SVI > 350 mL/g. The application of carriers increased the proportion of non-filamentous microorganisms to over 80%, reduced SVI to 150–400 mL/g, and increased MLSS to over 2700 mg/L, enabling stable operation. This study challenges the traditional negative perception of filamentous bacteria and opens new prospects for wastewater treatment technology. Full article

The filtration behaviors of dynamic membrane (DM) under gravity-driven and pump-driven modes were investigated in a pilot-scale DM bioreactor (DMBR) for domestic wastewater treatment. After DM formation, both modes achieved effective solid–liquid separation, producing effluent with turbidity below 1 NTU, with the gravity-driven module exhibiting marginally lower turbidity than the pump-driven system. Although the flux in the gravity-driven mode (30–48 L/m²·h) was approximately half that of the pump-driven mode, the transmembrane pressure (TMP) required was only 10–20% of that under the pump-driven operation. The DM formed under pump-driven conditions was thicker and more compact, leading to more frequent and rapid TMP increases. Inorganic content accounted for 85% of the pump-driven DM mass, significantly higher than that in the gravity-driven DM (50%) and activated sludge (15%), indicating a pronounced accumulation of inorganic solids on the mesh filter surface, particularly under the pump-driven operation. This accumulation increased filtration resistance and elevated TMP. Therefore, enhancing the removal of inorganic solids prior to the DMBR can improve system stability and facilitate broader application of the DMBR technology. Full article

This study investigates the operational performance and optimization of a real greywater treatment system utilizing aluminum (Al)-based electrocoagulation (EC). The EC process was systematically evaluated and optimized through Response Surface Methodology (RSM) using the Box–Behnken Design (BBD), focusing on three critical parameters: pH, current density, and electrolysis time. Greywater samples collected from domestic sources were characterized by key physicochemical parameters including pH, COD, TSS, turbidity-ty, and electrical conductivity. The electrochemical treatment was conducted using a batch reactor equipped with Al electrodes in a monopolar configuration. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), and Fourier-Transform Infrared Spectroscopy (FTIR) were employed to characterize both the electrodes and the generated sludge. Results revealed a maximum COD removal efficiency of 86.34% under optimized conditions, with current density being the most influential factor, followed by its significant interaction with pH. The developed quadratic model exhibited high predictive accuracy (R² = 0.96) and revealed significant nonlinear and interaction effects among the parameters. Sludge characterization confirmed the presence of amorphous aluminum hydroxide and oxyhydroxide phases, indicating effective coagulant generation and pollutant capture. The treated greywater met physicochemical criteria for non-potable reuse, such as agricultural irrigation, supporting resource recovery objectives. These findings demonstrate that EC is a low-waste, chemically efficient, and scalable process for decentralized wastewater treatment, aligning with the goals of sustainable chemical engineering. Full article

Resource utilization of water treatment residuals (WTRs) has emerged as a significant focus in environmental engineering research. In this study, waste iron sludge from a groundwater de-ironing plant was used as the raw material. Ferric salts were recovered via sulfuric acid leaching and subsequently polymerized into polyferric sulfate (PFS) with varying basicity (B = 0.1–0.4) using the alkalization–aging method. The optimal leaching conditions were determined as a liquid–solid ratio of 10:1, a sulfuric acid concentration of 3 mol·L⁻¹, a reaction temperature of 70 °C, and a reaction time of 30 min, yielding a ferric leaching amount of 0.45 g Fe/g dry sludge. Characterization results revealed that the synthesized PFS exhibited similar ferric polymer species, functional group structures, and polymeric crystal structures to those of commercial PFS (CPFS). Coagulation performance tests demonstrated that at a dosage of 30 mg Fe/L, the prepared PFS achieved turbidity and UV₂₅₄ removal efficiencies of 96.88% and 81.87%, respectively, outperforming CPFS. In domestic wastewater treatment, combining the synthesized PFS with magnetic nanoparticles Fe₃O₄@C yielded a magnetic coagulant that further enhanced the removal of turbidity, chemical oxygen demand (COD), and total phosphorus (TP) to maximum efficiencies of 94.66%, 81.97%, and 98.08%, respectively. This study confirms the technical feasibility and environmental–economic benefits of preparing magnetic PFS coagulants from waste iron sludge for wastewater treatment. Full article