Water Science and Technology最新文献

The transition from up-flow anaerobic sludge blanket (UASB) reactors to expanded granular sludge bed (EGSB) reactors presents challenges for traditional symmetric critical gas-liquid-solid (GLS) separators, including high spatial occupation, fluid-energy consumption, and reduced separation efficiency. This study introduced a novel GLS separation mechanism based on vortex circulation-induced deposition, agglomeration, and flowback of solid separation. Leveraging this mechanism, an innovative asymmetrical laboratory-scale GLS separator was developed and tested with both granular and flocculent sludge. The new prototype demonstrates superior solid separation performance, achieving 98.3% for granular sludge and 96.0% for flocculent sludge. It features a simple structure and optimized flow paths, resulting in approximately 30% reduction in height and 14.8% less material consumption compared to existing models. Flocculent sludge shows greater sensitivity to operational factors than granular sludge, with higher sludge concentration and smaller fragment size being preferable for high separation efficiency. This mechanism is validated by experimental observations and computational fluid dynamics (CFD) simulations, providing a new perspective on GLS separation and establishing the new model as a promising candidate for UASB/EGSB bio-reactors.

Flow measurement and water level control in open channels are vital to water management. Lateral intake structures are commonly used for different purposes in civil and environmental engineering applications. Flow characteristics of rectangular, triangular, and semi-circular shapes were experimentally investigated using 357 runs under subcritical flow conditions. Correlation analysis was conducted to determine the effect of various parameters on the discharge coefficient. Upstream Froude number (F₁), the ratio of the gate opening to the upstream flow depth, and the gate length to flow depth ratio are influential for all side gates. However, the ratio of the gate opening to the gate length is also influential for triangular side gates. Discharge coefficient of the semi-circular side gate is relatively higher than that of the other tested gates within the range of 0.051<0.40; the discharge coefficient of the triangular side gate is relatively higher than that of the other shaped gates for 0.401<0.98 and the efficiency of the triangular side gate decreases more than that of the other gates as the downstream Froude number value increases. A reliable equation for side gates was developed. Good agreements were obtained between the proposed equations and the experimental data.

Ultrafiltration membranes are widely used in the treatment of surface water. However, membrane fouling is a core issue that needs to be addressed in its application. Magnetotactic bacteria (MTB) show early film-forming and magnetotactic behaviour in the presence of external magnetic fields. The objective of this study was to alleviate membrane fouling in ultrafiltration membranes using MTB, which can prioritise film formation and show directional movement under external magnetic fields. The concentration of Cr⁶⁺ in the water was 10 mg/L, and the dosage of MTB was 10 mg/L. Results show that the transmembrane pressure of the ultrafiltration membrane decreased by 5 kPa following the application of a magnetic field of 33.71 mT for a period of 90 min, and the membrane fouling could therefore be effectively controlled. With the addition of MTB, the average removal of Cr⁶⁺ from water by the ultrafiltration system was 20.10%, which was 14.56% higher than that of the conventional ultrafiltration system. The average removal of chromaticity was 20.13%, which was 10% higher than that achieved by the conventional ultrafiltration system. Furthermore, MTB progressively developed into the predominant flora during the operational phase, thereby enhancing the efficiency of the ultrafiltration system.

One of the most costly stages of activated sludge wastewater treatment plants is the treatment and dewatering of waste sludge. Chemical conditioning of sludge, as one of the most widespread methods to enhance sludge dewaterability, accounts for a significant portion of operational expenses due to the consumption of expensive polymeric compounds. This research aims to assess the cost-effectiveness of ochre soil, modified with hydrochloric acid, as an affordable mineral for conditioning waste sludge in an activated sludge system. The optimal conditions for acid modifications are obtained using response surface methodology. Then, its performance is compared with conventional coagulants (ferric chloride and alum) and in combination with cationic polyacrylamide (CPAM). To assess the conditioning process efficiency, the specific resistance to filtration (SRF) parameter was employed. At an optimal dose of modified ochre soil (MOS) equal to 300 (mg/g dry solids), the SRF value decreased from 31.96 to 2.7 Tm/kg. The combination of 100 (mg/gDS) MOS with 0.5 (mg/gDS) CPAM showed as the most cost-effective among the coagulants tested, with a 31% greater SRF reduction compared to CPAM used alone. This study shows the practical efficacy of an eco-friendly natural mineral as a polymer alternative, with the potential for sludge dewatering.

Nowadays, performance studies on the amperometric total residual oxidant (TRO) sensor are only in the bench test stage and have not been conducted under specific maritime conditions with Ballast Water Management System (BWMS). In this study, the application of the amperometric TRO sensor in land-based biological efficacy (BE) testing, operation and maintenance (O&M) testing, as well as shipboard (SB) testing, was explored by comparing with the existing di-phenylene-diamine (DPD) TRO sensor. The results showed that the average TRO measurement deviation between the amperometric sensor and the DPD sensor was within ±10% in valid BE test cycles and the O&M testing exceeding 47 operating hours. The TRO value measured by amperometric sensor exhibited significant fluctuations, but the improved control logic could achieve smoothing out the fluctuation, with stability comparable to or even higher than that of the DPD sensor. The practicality and reliability of the amperometric sensor in electrochlorination-based BWMS were further verified through SB testing.

This work focused on the biotreatment of wastewater and contaminated soil in a used oil recycling plant located in Bizerte. A continuous stirred tank reactor (CSTR) and a trickling filter (TF) were used to treat stripped and collected wastewater, respectively. The CSTR was started up and stabilized for 90 days. Over the following 170 days, the operational organic loading rates of the TF and the CSTR were around 1,200 and 3,000 g chemical oxygen demand (COD) m^-3 day^-1, respectively. The treatment efficiency was 94% for total petroleum hydrocarbons (TPHs), 89.5% for COD, 83.34% for biological oxygen demand (BOD₅), and 91.25% for phenol. Treated industrial wastewater from the TF was used for bioaugmentation (BA) of contaminated soil. The assessment of the soil took 24 weeks to complete. The effectiveness of the soil BA strategy was confirmed by monitoring phenolic compounds, aliphatic and polycyclic aromatic hydrocarbons, heavy metals, and germination index. The biodegradation rate of contaminants was improved and the time required for their removal was reduced. The soil bacterial communities were dominated by species of the genera Mycobacterium, Proteiniphilum, Nocardioides, Luteimicrobium, and Azospirillum, which were identified as hydrocarbon and phenol-degrading bacteria.

Heavy metals pose a significant threat to human health, with contaminated water sources linked to severe conditions, including gastric cancer. Consequently, the effective remediation of heavy metals is crucial. This study employs a bibliographic analysis to examine key methodologies, leading organizations, and prominent countries involved in heavy metal remediation. By systematically reviewing around 1,000 records, the paper identifies the most critical remediation techniques and provides a comprehensive overview of current practices in the field. Additionally, the study explores prospects, emphasizing the potential of emerging technologies such as big data and machine learning to enhance remediation efforts. It highlights recent advancements, identifies significant trends, such as the growing use of bioremediation and nanotechnology, and addresses critical challenges in the remediation landscape, including regulatory hurdles and technological limitations. By making stronger connections between the identified trends and their implications for future research, this comprehensive analysis aims to provide valuable insights and guide the development of improved strategies for mitigating the impact of heavy metal contamination, ultimately safeguarding public health.

This review examines the potential for utilizing nuclear power plant (NPP) waste heat in hybrid desalination systems, focusing on Reverse Osmosis-Low-Temperature Evaporation (RO-LTE) driven by renewable energy sources and atomic waste heat. By employing a SOAR (Strengths, Opportunities, Aspirations, Results) analysis, the study evaluates the integration of NPP waste heat into various desalination technologies, emphasizing the environmental benefits and energy efficiency improvements. Fundamental aspirations include advancements in material science and heat exchanger designs, which enhance heat transfer and evaporation processes. The review also explores cost reduction strategies, such as integrating hydrogen production and mineral recovery from desalination by-products. Passive technologies and process optimization are proposed to minimize operational costs and energy consumption, supporting long-term sustainability. This review serves as a resource for decision-makers, offering insights into the strategic use of NPP waste heat in desalination to address water scarcity while promoting energy efficiency and sustainability.

Granular activated carbon (GAC) and GAC modified with anthraquinone-2-sulfonate (AQS) were used as conductive materials during the anaerobic digestion of swine wastewater (SW). The electron transfer capacity (ETC) in the GAC-AQS was 2.1-fold higher than the unmodified GAC. Despite the improvement in the ETC, the GAC-AQS cultures showed an inhibitory effect, evidenced by the lowest methane productivity. Indeed, the cultures with unmodified GAC achieved 236 mL CH₄/g COD_i (chemical oxygen demand, initial), representing an increment of 1.14- and 2.05-fold compared with the control (without conductive materials) and GAC-AQS, respectively. In addition, the methane production rate (R_max) and yield were also improved with unmodified GAC, but they decreased with GAC-AQS. The role of solid-phase AQS (GAC-AQS) as a terminal electron acceptor during microbial respiration competes with methanogenesis for the electrons instead of serving as an electron conduit.

The need for stringent phosphorus removal from domestic wastewater is increasing to mitigate eutrophication, while efficient phosphate reuse is critical due to the global phosphate crisis. Combining aluminum sulfate (ALS) with high molecular weight organic polymers achieved 95-99% removal of particles, turbidity, and phosphates, reducing ALS usage by 40%. We propose mechanisms to explain the enhanced treatment efficiency. Particle and turbidity removal is more influenced by polymer charge density than molecular weight, while orthophosphate (OP) removal is linked to a change in zeta potential from negative to positive, allowing additional OP binding through complex formation with hydrolysis products and polymers. Enhanced phospholipid (PL) removal likely results from adsorption and neutralization of micelle PL charges by intermediate positively charged aluminum hydroxyphosphate ions. Higher PL removal with low ALS doses is attributed to a two-stage dosing process that optimizes coagulant and polymer dosages. The combined removal of OP and PL improves phosphorus bioavailability, increasing the sludge's fertilizer value.