Water Environment Research最新文献

In this study, the pollution levels of Alibeykoy Dam Lake were assessed by examining phytoplankton distribution, physicochemical parameters, nutrient content, and heavy metal concentrations. Alibeykoy Dam is a critical drinking water source for the Istanbul metropolitan area. Water samples were collected from the lake and six influent streams (Cebeci, Pirincci, Sidan, Bolluca, Gulgen, and Kocaman) in January, February, May, and September of 2021. A total of 36 taxa from seven divisions were identified, including Bacillariophyta (14), Charophyta (2), Chlorophyta (9), Cryptophyta (1), Cyanobacteria (3), Euglenozoa (4), and Miozoa (3). Diatoms were found to be the dominant group in terms of species richness and abundance. The dominant species recorded in each site were as follows: Microcystis aeruginosa in Alibeykoy Dam and Sidan Creek, Cyclotella ocellata in Cebeci and Gulgen Creeks, Scenedesmus sp. in Pirincci Creek, Navicula cryptocephala in Bolluca Creek, and Sphaerocystis planctonica in Kocaman Creek. Mesotrophic and eutrophic phytoplankton species suggested that the lake is nearing eutrophic conditions. This conclusion was further supported by high concentrations of heavy metals and nutrients detected in the water samples. This research is significant because it provides a comprehensive understanding of the ecological status of Alibeykoy Dam Lake, a critical resource for drinking water in Istanbul. The study highlights potential risks associated with eutrophication and heavy metal accumulation by identifying pollution levels and dominant species. These findings are vital for implementing effective water resource management strategies, ensuring the lake's sustainability, and protecting public health. PRACTITIONER POINTS: The pollution rate of Alibeykoy Dam Lake was determined. The presence of mesotrophic and eutrophic species of phytoplankton indicated the lake's trophic structure. The measurements were done to estimate the lake's heavy metal and nutrient contents.

Microalgal-bacterial aggregates are promising for wastewater treatment because they remove organic matter, nitrogen, and phosphorus while producing biomass that settles quickly. This review details the development of microalgal-bacterial aggregates, identifies key challenges, and proposes future research directions. While many studies have been performed in the laboratory with synthetic wastewater and artificial lighting, more research is needed to better understand how to form and sustain aggregates at larger scales with real wastewater and natural lighting. While it appears that microalgal-bacterial aggregates are unlikely to replace or augment conventional activated sludge, they have the potential to improve resource recovery in existing microalgae-based wastewater treatment processes (e.g., high-rate algal ponds). Alternatively, attached-growth bioreactors utilizing microalgal-bacterial consortia may be able to compete directly with conventional activated sludge while providing the benefits that microalgae offer, although additional research is needed. PRACTITIONER POINTS: More pilot and full-scale research on microalgal-bacterial processes is needed. Microalgae cultivation with short retention times is challenging. Attached-growth processes may allow for competitive footprint requirements.

The effluent produced from treating landfill leachate via biological methods still contains a large amount of refractory organic matter and needs to be further treated. In this study, we used a microwave-enhanced zero-valent iron/peroxydisulfate (MW/Fe⁰/PDS) system for the further treatment of biotreated landfill leachate effluent (BTLE). We investigated the efficiency and mechanism of removing refractory organic matter from BTLE. The results show that under the conditions of MW = 240 W, [PDS]₀ = 40 mM, [Fe⁰]₀ = 10 mM, and t = 12 min, the MW/Fe⁰/PDS system best removed organic matter in the BTLE. The removal rates of UV absorbance at 254 nm, color number, and total organic carbon reached 76.94%, 93.50%, and 63.08%, respectively. The aromaticity, degree of humification, molecular weight, and degree of polymerization of the organic matter decreased significantly. The surface morphology and elemental valence analysis of Fe⁰ before and after the reaction revealed that iron-based oxides (i.e., Fe₂O₃, Fe₃O₄, FeOOH, and Fe (OH)₃) formed on the surface of Fe⁰. The refractory organic matter was removed by homogeneous and heterogeneous Fenton-like reactions and the adsorption-precipitation of iron-based colloids. The thermal and nonthermal effects of MW promoted direct PDS decomposition, accelerated the formation of Fe²⁺ on the surface of Fe⁰, promoted the redox cycle of Fe³⁺/Fe²⁺, and generated more sulfate radicals (SO₄ ^•-). Together, these effects improved the removal efficiency  of refractory organic matter. The results of this study can serve as a theoretical basis for the use of the MW/Fe⁰/PDS system to treat refractory organic matter in BTLE. PRACTITIONER POINTS: A microwave-enhanced Fe⁰/PDS system is effective for removing organic matter from landfill leachate. Colored and fluorescent organic matter in the landfill leachate was efficiently degraded. Heterogeneous and homogeneous effects Fenton reactions are involved in the system.

Practitioners often use specific UV₂₅₄ absorption (SUVA) as an indicator of hydrophobic (HPO) dissolved organic carbon (DOC) to evaluate removal efficiency and estimate trihalomethane formation potential (THMFP). However, current fractionation methods, such as solid-phase extraction (SPE), primarily focus on recovering sorbed compounds, and assume that treatment impacts only the quantity, not the characteristics, of DOC fractions. Additionally, varying recovery rates and inconsistent fractionation pH definitions complicate cross-study comparisons of hydrophilic and HPO DOC composition. To address these issues, we tested three pH fractionation approaches (pH 3, pH 7, and sequential adjustment) and observed significant differences in DOC content, SUVA, and specific THMFP (STHMFP) between SPE filtrates at pH 3 and pH 7, which were most likely because of ionizable acidic DOC compounds becoming HPO at lower pH levels. Based on these findings, we developed a new fractionation method to estimate the quantity and characteristics of major DOC fractions-hydrophilic neutral (HPIN), total acidic (TA = HPOA + HPIA), and hydrophobic neutral (HPON)-without the need to recover sorbed fractions. Applying this method in a conventional coagulation/softening plant revealed HPON decreased while the relative amounts of HPI and TA increased after the treatment. However, the treated water HPI exhibited significantly higher STHMFP and contained approximately twice the proportion of low-molecular-weight compounds than raw water HPI, highlighting significant changes in both the content and properties of DOC fractions throughout the treatment process. Our study indicates that the contribution of HPI DOC fraction to SUVA and STHMFP in treated water is greater than that of HPO DOC. PRACTITIONER POINTS: A two-stage ENV to estimate major DOC fractions without recovering sorbed compounds. One ENV cartridge at pH 3 can effectively isolate HPI DOC, replacing sequential ENV. Coagulation and lime/soda softening altered characteristics of DOC fractions. HPI DOC in treated water contributes to SUVA and STHMFP more than HPO fraction.

Increasing nutrient concentrations in fish culture systems over time can reduce water quality. However, the nutrient increase can be remediated by pairing organisms at lower trophic levels with a mechanical filtration system to improve nutrient removal efficiency and water quality for fish culture. This research uses the RAS system to determine the performance of integrating living organisms as biofilters in rearing juvenile rainbow trout (Oncorhynchus mykiss) for 56 days. Duckweed (Lemna minor) was added to replicate tanks at three treatment levels: T1 (100 g wet weight and 20% area coverage), T2 (200 g wet weight and 40% area coverage), and T3 (300g wet weight and 60% area coverage). The duckweed in each treatment tank was supplemented with 20 freshwater mussels (Anodonta cygnea) with an average body weight of 56 ± 1.0 g. Physical and chemical water quality parameters were measured in fish tanks and all ponds in the RAS system. Fish from the rearing tanks were weighed every two weeks. Duckweed biomass was measured weekly; the mussels were weighed at the beginning and end of the study, and the mussels were measured at the beginning and end of the rearing period. The fish was partially harvested every two weeks to maintain constant fish biomass. Using duckweed (L. minor) with different biomass weights and areal coverage, coupled with the freshwater mussels (A. cygnea) as living biofilters, had a significant effect (P < 0.05) on water quality parameters. Ammonium (NH₄), nitrite (NO₂), and nitrate (NO₃) concentrations decreased throughout the study. During the study period, juvenile trout experienced growth with an SGR of 2.62-2.72%/gram with a survival rate of 100%. Partial harvesting during the rearing period positively impacted the average body weight of fish growth and duckweed biomass. The best duckweed growth performance was found in treatment T1 (cover area 20% with wet weight 100 g) with a productivity of 9.4 (g/m²/day). PRACTITIONER POINTS: Twenty percent duckweed coverage with freshwater mussels achieves optimal nutrient removal in RAS systems, improving water quality efficiently and growth better than other treatments. Combined biofilters (duckweed-mussel) and filtration units reduce operational costs while maintaining high fish survival rates in RAS systems. Integration of living biofilters provides sustainable water treatment without chemical additives, suitable for small-scale aquaculture operations.

The Fenton-like process, utilizing zero-valent iron (Fe⁰) and hydrogen peroxide (H₂O₂), is employed to degrade refractory organic matter in membrane bioreactor (MBR) effluent derived from landfill leachate. However, the rate-limiting Fe²⁺/Fe³⁺ redox step diminishes treatment efficacy and generates substantial iron sludge. This study elucidates the mechanism by which ultraviolet (UV) irradiation augments the Fe⁰/H₂O₂ process for the removal of refractory organic matter in MBR effluent. The results show that the UV- enhanced H₂O₂ process effectively disrupts the aromatic structure of organic compounds, reducing molecular weight, degree of polymerization, and humification. Compared with the Fe⁰/H₂O₂ process, the removal efficiency of UV₂₅₄, color number, and total organic carbon in the effluent treated by the UV/Fe⁰/H₂O₂ process increased by 24.16%, 14.62%, and 57.46%, respectively. Concurrently, the generation of iron sludge was reduced by 21.6%. This enhancement is primarily attributed to UV's ability to intensify the Fe²⁺/Fe³⁺ redox cycle and expedite the surface corrosion of Fe⁰, yielding more iron oxides. This accelerates the decomposition of H₂O₂, generating a higher quantity of ^•OH through both homogeneous and heterogeneous Fenton-like reactions. The refractory organic matter is removed through the oxidation by ^•OH, as well as the adsorption and precipitation facilitated by iron-based colloids. PRACTITIONER POINTS: UV promotes Fe⁰/H₂O₂ process to degrade refractory organic matter in MBR effluent. UV promotes Fe⁰ to dissolve more Fe²⁺ and the redox cycle of Fe²⁺ and Fe³⁺. The dosage of H₂O₂ or Fe⁰ influences the treatment effect of the process.

Plastics pollutants, especially microplastics (MPs, <5 mm in diameter) and levofloxacin hydrochloride (Lev-HCl) often co-exist in the aquatic environment. To explore the adsorption processes and mechanisms of Lev-HCl by non-degradable MPs, in this study, H₂O₂ oxidation was used to age polyvinyl chloride (PVC), polystyrene (PS), and polyethylene terephthalate (PET) MPs. The results demonstrated that the equilibrium adsorption capacity increased significantly after aging, as H₂O₂-PET (1.167 mg/g) > PET (0.995 mg/g), H₂O₂-PS (1.057 mg/g) > PS (0.957 mg/g), H₂O₂-PVC (1.107 mg/g) > PVC (0.975 mg/g). After H₂O₂ aging, the hydrogen bond (-OH) was more obvious, and π-π interactions were significantly enhanced. These non-degradable MPs mainly adsorbed Lev-HCl by micropore filling (contributions: PVC 65.9%, PS 56%, PET 63.5%). The current study highlights the potential of non-degradable MPs to act as a vector for Lev-HCl in the aquatic environment, especially after H₂O₂ aging. PRACTITIONER POINTS: Adsorption behavior of Lev-HCl onto three non-degradable MPs was elucidated. The adsorption capacity increased significantly after aging for PVC, PS, and PET MPs. The hydrogen bonding and π-π interactions of H₂O₂-aged MPs were more significant. Multi-layer adsorption on non-homogeneous surfaces via micropore filling was revealed.

Macrophyte extracts inhibit cyanobacteria growth, offering a sustainable solution for bloom control. The present study aimed to evaluate the response of Microcystis aeruginosa to aqueous extracts obtained from the dried biomass of Pistia stratiotes L. and Pontederia crassipes Mart. Solms. The parameters analyzed were cyanobacterial growth, photosynthesis, generation of reactive oxygen species, and antioxidative response. The chemical profile of the aqueous extracts upon incubation was also analyzed. Both extracts (4.0 g.L^-1) inhibited cyanobacterial growth in 6 days: 100% inhibition for P. stratiotes and 60% inhibition for P. crassipes. Photosynthetic activity was also inhibited: 99% inhibition for P. stratiotes and 12% inhibition for P. crassipes. This was related to the downregulation of the psbA gene (coding for the photosystem II protein D1). Exposure to both extracts increased the concentration of intracellular reactive oxygen species in cyanobacterial cultures. Superoxide dismutase( SOD) enzymatic activity increased in cultures exposed to P. stratiotes extracts. The transcription of the sod gene was not altered but the transcription of the peroxiredoxin gene (prxA) increased. Upon incubation of the macrophyte extracts with M. aeruginosa cultures, phenol concentrations decreased, and their metabolic profile changed. Thus, P. stratiotes extract outperformed P. crassipes in inhibiting M. aeruginosa growth. P. stratiotes extracts obtained from the plant dry biomass present allelopathic activity on cyanobacteria and can be used as a sustainable alternative to mitigate blooms. PRACTITIONER POINTS: Aqueous extracts from dried biomass of P. stratiotes and P. crassipes inhibited M. aeruginosa growth. P. stratiotes extract suppressed photosystem II activity, while P. crassipes did not. Both extracts elicited reactive oxygen species (ROS) production in cells. Peroxiredoxin gene expression upregulated by extract exposure. P. stratiotes extract increased superoxide dismutase (SOD) activity in cells.

Microplastic (MPs) pollution has engulfed global aquatic systems, and the concerns about MPs translocation and bioaccumulation in fish, crabs, and other marine organisms are now an unpleasant truth. In the past few years, MPs pollution in freshwater systems, particularly rivers, and subsequently in freshwater organisms, especially in crabs, has caught the attention of researchers. Rivers provide livelihood to approximately 40% of the global population through food and potable water. Hence, assessment of emerging contaminants like MPs in waterways and the associated fauna is crucial. This study assessed MPs in crab S. serrata across the largest riverine system of south India, the Kaveri River. The MPs were characterized by optical microscopy, and field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX) analysis for their number, shape, size, and color. Polymer composition was analyzed using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and Raman spectroscopy. Polypropylene (PP), polystyrene (PS), polyamide (PA), and polyvinyl chloride (PVC) were the dominant plastic polymers in the crab intestine. Additionally, the FE-SEM analysis revealed that the MPs have differential surface morphology with rough surfaces, porous structures, fissures, and severe damage. Most MPs comprised Na, Si, Mg, Cl, K, and Ca, according to EDX analyses. The findings might provide insight into the status of MPs in S. serrata at Kavery river that could help in formulating regulations for MPs reduction and contamination in rivers eventually to protect the environment and human health. PRACTITIONER POINTS: The first findings on the identity and properties of MPs in crabs from the Kaveri River at Mettur Dam. A simple and cost-effective approach for extracting microplastics from crab samples from Mettur Dam, Kaveri River, Salem District, Tamil Nadu, India. Microplastics were detected using optical microscopy, ATR-FTIR, and FE-SEM.

A Cu-Ce@γ-Al₂O₃ catalyst was developed for the efficient treatment of chemical reverse osmosis (RO) membrane concentrate wastewater. The working conditions and reaction mechanisms of Cu-Ce@γ-Al₂O₃ catalytic ozonation were systematically investigated, and its application in the catalytic ozonation of chemical RO membrane concentrate wastewater was explored. The catalyst was comprehensively characterized using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), and Fourier-transform infrared (FTIR) spectroscopy, revealing its microstructure, elemental composition, and crystal structure. The optimal reaction conditions were identified as follows: ozone dosage of 8 mg/L/min, initial pH of 9.0, catalyst filling ratio of 10%, and a reactor height-to-diameter ratio of 5:1. Under these conditions, the catalytic ozonation achieved a chemical oxygen demand (COD) removal rate of 63.4%. Free-radical quenching experiments confirmed that hydroxyl radicals (·OH) played a dominant role in the catalytic ozonation system. Kinetic analysis revealed that the catalytic ozonation of chemical RO membrane concentrate wastewater with Cu-Ce@γ-Al₂O₃ followed second-order kinetics. The degradation mechanisms of organic matter in the wastewater were further analyzed using ultraviolet-visible (UV-Vis) spectroscopy and three-dimensional fluorescence spectroscopy. Additionally, a weighted rank sum ratio (WRSR) evaluation model was developed to provide a comprehensive assessment of the process performance. PRACTITIONER POINTS: Cu-Ce@γ-Al₂O₃ catalysts with excellent catalytic performance were prepared. Efficient catalytic ozonation of chemical RO membrane concentrate with high salinity was realized. Degradation mechanism of organic pollutants by catalytic ozonation is clarified. Evaluation model for catalytic ozonation of chemical RO membrane concentrate was established.