Water Science and Technology最新文献

Human activities are intricately linked to entropy changes, inevitably impacting the ecological environment. The initial transportation of urban pipe network systems plays a critical role in this process. These systems involve processes such as fermentation, hydrogen production, acetic acid production, and methane production, generating gases, such as methane and carbon dioxide. Despite their importance, the mechanisms underlying entropy changes during organic matter degradation remain underexplored. This study establishes a 1,200-m-long urban sewer pilot system to analyze pollutant degradation through reaction equations. A novel method, based on standard molar reaction enthalpy changes, is developed to calculate entropy changes, revealing distinct stages of entropy increase. Results indicate that environmental entropy rises primarily during sugar degradation and acetic acid production, while entropy decreases during glucose degradation and methanogenesis. During sewage transport, the heat released from pollutant degradation exceeds that associated with greenhouse gas emissions, leading to a general increase in entropy in the external environment. The findings of this study could help to predict the actual influent quality of wastewater treatment plants and facilitate the optimization of wastewater treatment.

Dark fermentation has the potential to produce biohydrogen using raw material waste, such as wastewater from the corn industry (cornWW), which is characteristically alkaline and improperly discharged. This study aimed to assess the impact of different hydraulic retention times (HRT) on hydrogen production in a sequencing batch reactor system using raw cornWW as feedstock. Different HRTs were evaluated (4, 2, and 1 day(s)). Higher biohydrogen productivity was observed in HRT value of 1 day (893.6 ± 10.1 NmL H₂/L_reactor/day), indicating its favorable metabolic pathways leading to the generation of hydrogen, carbon dioxide, acetate, butyrate, and caproate. Microbial analysis revealed that the Atopobium and Clostridium (genera) played key roles in hydrogen and organic acid production. Additionally, during the fermentation of cornWW, lactic acid in the feedstock facilitated the production of caproic and propionic acids, further enriching the range of valuable byproducts obtained through this process.

Life cycle assessment (LCA), coupled with process modeling to develop the life cycle inventory, is a valuable tool to assess differences in environmental performance when evaluating alternatives based on sustainability (triple-bottom-line) principles. Coupled with a whole plant process model (SUMO21), an LCA assessed the environmental performance of options to upgrade biosolids management for the Great Lakes Water Authority water resource recovery facility. All five alternatives evaluated (composting plus four anaerobic digestion alternatives) were able to meet the core objectives of the biosolids management system upgrade: (1) address ageing incinerators, (2) minimize the mass of biosolids landfilled, and (3) reduce greenhouse gas emissions, compared to the existing (baseline) system. The mass of solids to be managed was reduced for the anaerobic digestion alternatives but not for the composting alternatives. Environmental impacts were reduced for the composting alternative for all six impact categories considered (global warming, eutrophication, carcinogenics, ecotoxicity, respiratory effects, and fossil fuel depletion) relative to the baseline, and further reduced for all four anaerobic digestion alternatives evaluated. The results allowed a phased implementation plan to be developed, which could be evaluated based on other factors, such as costs and operational factors.

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.

Naphthenic acids are the most significant environmental pollutants created by the extraction of oil from oil sand deposits. Since the diffusion coefficient of naphthenic acid has a direct effect on the modeling of diffusion and advection and determining its behavior and movement in water, this number is needed for modeling work and future studies. In this study, the diffusion coefficient of this substance in water was determined experimentally and in a laboratory. The researchers used the device of the Armfield company, known as the device for determining the diffusion coefficient in liquids. In this research, after examining different methods of determining the concentration of naphthenic acid in the water, including UV-vis, chemical oxygen demand (COD), crystal violet, oxidation reduction potential, pH meter, and electrical conductivity meter, the COD method was the best method in determining the concentration at different times, which provided a suitable numerical range for the concentrations and a device was built for heavy oil pollutants with poor solubility in water to specify the diffusion coefficient, and for the first time, the diffusion coefficient of naphthenic acid in water was obtained with experiments and experimental equations as 0.69 × 10^-9 m²/s which indicates the weak diffusion of this substance in water.

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.