Water Environment Research最新文献

This study evaluates the performance of three constructed wetland (CW) configurations: horizontal flow (HFCW), vertical flow (VFCW), and hybrid vertical-horizontal flow (HVHCW)-for the treatment of domestic wastewater in a decentralized context in India. A pilot-scale system was operated under real wastewater loading for 8 weeks, with weekly sampling (n = 8 per system) and triplicate analysis per sample. Key water quality parameters assessed included biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), ammonia nitrogen (NH₃-N), nitrate nitrogen (NO₃-N), and total phosphorus (TP). Analytical protocols followed APHA (2017) standard methods. The HVHCW configuration achieved the highest removal efficiencies, with mean values of 94.4% for BOD and 96.8% for TSS, outperforming both single-stage systems. One-way ANOVA revealed statistically significant differences (p < 0.05) across systems for most parameters, and Tukey's HSD post hoc test confirmed HVHCW's superiority. Nitrate removal, while observed, was not statistically significant (p > 0.05), indicating the need for design enhancements to support denitrification. These results underscore the potential of hybrid CWs as low-cost, eco-sustainable solutions for decentralized wastewater management in developing regions.

Achieving decoupling between water pollution and economic growth is a critical governance challenge in resource-based economies (RBEs). The classic environmental Kuznets curve (EKC) hypothesis often fails in such regions due to "policy trade-offs," such as the conflict between energy security and environmental protection goals. Simultaneously, existing methodologies tend to bifurcate the analysis of long-term structures and short-term shocks. This paper, using data from China's Shanxi Province (2010-2024) as a typical case, constructs a "multi-scalar diagnostic framework" that integrates principal component analysis (PCA), the EKC, and the Tapio decoupling model. Empirical results show the following: (1) During the study period, the relationship between water pollution and economic growth in Shanxi was predominantly in a state of weak decoupling. However, the Tapio model also revealed recent "expansive negative decoupling" events, indicating that short-term pressures persist. (2) The EKC analysis reveals a "differentiated path": industrial pollution indicators, including industrial wastewater, COD, and ammonia nitrogen, exhibit an inverted U-shape, suggesting industrial governance is aligning with economic growth. (3) In contrast, the EKC curve for domestic ammonia nitrogen shows a distinct N-shape, indicating that pressure from domestic wastewater discharge continues unabated. (4) Notably, this N-shaped curve appears to have passed its second turning point, with domestic ammonia nitrogen emissions showing a downward trend after peaking. This study's theoretical contribution is the revelation that the N-shaped curve is the cumulative consequence of "policy trade-offs" in RBEs. These short-term policy shocks, captured by the Tapio model, constitute the micro-foundations for the distortion of the long-term (N-shaped) EKC structure, reflecting a governance model that prioritizes industrial and energy objectives while relatively neglecting municipal environmental governance.

Replacing conventional filter media with recycled filters can enhance treatment efficiency and reduce the operational cost of vertical subsurface flow constructed wetlands (VSF CWs). This study evaluated the feasibility of using oyster shells (Crassostrea gigas) and polyethylene plastic waste as substitutes for traditional gravel media in VSF CWs treating swine wastewater. Seven media configurations were designed: CP1 (sand, small gravel [1 × 2 cm], and large gravel [3 × 5 cm]); CP2 and CP3 replaced small gravel with oyster shells and plastic waste, respectively; CP4, CP5, and CP6 used mixtures of oyster shells and plastics in varying volume ratios (1:3, 1:1, and 3:1, respectively); CP7 was a control system with no media. Four-month experiments were conducted at a laboratory scale, monitoring different hydraulic retention times (HRTs) (1, 2, 3, and 4 days) under two conditions: planted with Cyperus alternifolius and unplanted. Importantly, replacing conventional filter media with oyster shells and plastic waste did not adversely affect the growth of C. alternifolius in any of the experimental systems. The results showed that planted systems achieved 0.8%-28.7% higher removal efficiencies than unplanted ones (p < 0.05), with an optimal HRT of 2-3 days to meet QCVN 62-MT:2016/BTNMT Column B. CP1 consistently demonstrated the highest treatment efficiency. Meanwhile, CP2 and CP6 exhibited slightly lower removal efficiencies than CP1 but still achieved outstanding TP removal rates of over 70%. CP3 showed the lowest treatment performance. However, its effectiveness could be improved by blending with oyster shells at appropriate ratios. Among all experiments using recycled filter media, CP6 exhibited the most promising performance, with removal efficiencies for TSS, COD, TN, NH₄ ⁺, and TP ranging from 62.6% to 87.6%, 36.1% to 77.2%, 30.8% to 74.0%, 33.6% to 85.3%, and 29.6% to 69.0%, respectively. Substituting small gravel with recycled plastic waste and oyster shells reduces material costs by three to four times, mitigates environmental pollution, and promotes solid waste recycling toward a circular economy.

Green manure as phytoremediation can help with the technical feasibility of growing vegetables irrigated with dairy effluent treated by an anaerobic system (ANE). The objective of this study was to evaluate the production of lettuce cultivated in conjunction with table beet following the irrigation of green manure with treated effluent from a dairy processing plant and its impact on the chemical characteristics of the soil. The experimental design utilized a randomized blocks, factorial scheme, employing two water sources (tap water [TW], dairy effluent treated by an ANE) and four green manures, with four replicates. At the 45-day transplantation (DAT) mark, lettuce plants were analyzed, and at the 73-day DAT, the table beet. Lettuce demonstrated enhanced productivity in succession to pigeon pea, irrespective of water source, with productivity values of 2.28 kg m^-2 for TAP and 2.76 kg m^-2 for ANE. The nutrient supply by the effluent had a positive influence on the production of table beet roots when in succession to jack bean, Crotalaria juncea, and pigeon pea, with values of 3.76, 3.50, and 3.50 kg m^-2, respectively. Furthermore, the cultivation of lettuce and table beet in succession to green manures led to a reduction in sodium levels, resulting in a decrease in the exchangeable sodium percentage of irrigated soil treated with dairy effluent from 4.33% to 1.97%.

Membrane fouling is widely recognized as a significant drawback of membrane technology, as it reduces filtration flux and impairs the overall efficiency of wastewater treatment systems. Accurate prediction of membrane fouling, therefore, offers a crucial pathway to optimizing system operation and developing proactive mitigation strategies. This study developed machine learning models-including linear regression, support vector regression, and decision tree regression-to predict transmembrane pressure, a key indicator of fouling severity. Input descriptors such as pH, ammonium, nitrate, and alkalinity, measured at multiple stages of the anoxic-aerobic membrane bioreactor system, were used to train and evaluate the models. Among the tested approaches, nonlinear models-particularly decision tree regression-demonstrated superior performance, achieving high prediction accuracy (R² = 0.99). Moreover, machine learning helped identify the most influential input descriptors and uncover hidden patterns within the collected data. This study presents a promising alternative approach for predicting membrane fouling in wastewater treatment systems.

The temporal variation of 2-Methylisoborneol (2-MIB) and Geosmin (GSM) production in two filamentous cyanobacteria species, Pseudanabaena galeata and Phormidium ambiguum, was tested under three temperature regimes (20°C, 30°C, and 40°C). The 20°C is considered the ideal cultural temperature for both species. The 2-MIB, GSM, cellular H₂O₂, pigmentation, and total protein were quantified every other day for a 10-day period. Both species showed temporal variation in the measured parameters, but the variations were distinct between the two species. P. galeata showed significant changes in odor compound production at 40°C compared with 20°C and 30°C, recording a maximum 2.4-fold increase of 2-MIB and an 8.2-fold increase of GSM. P. ambiguum showed significant changes at 30°C and 40°C. 2-MIB of P. ambiguum increased a maximum of 13-fold at 30°C and 19-fold at 40°C, and GSM increased by 17-fold at 30°C and 4.6-fold at 40°C. The total chlorophyll content, H₂O₂ contents, and protein contents were also recorded with significant changes. No significant relationships were observed between odor compounds and other parameters.

Continuous bioaugmentation is widely employed across the pulp and paper industry in attempts to improve the resilience of wastewater treatment systems or the performance of undersized (in terms of volume, aeration, or nutrient supply) systems. Bench and field scale research into bioaugmentation has shown that success is often unpredictable. A field scale trial at an aerated lagoon system treating pulp and paper mill wastewater was completed over a 6-month period. The system consisted of two nearly identical trains of aerated stabilization basins (ASBs), one operated as a control and the other treated with a commercially available bioaugmentation product. The control and treated basins were then switched to minimize train-specific effects. Throughout the trial, changes in soluble or total biochemical oxygen demand (sBOD5 and TBOD5, respectively) or total suspended solids (TSS) at the first of the two ponds in series were not associated with bioaugmentation. In the second set of ponds, bioaugmentation was associated with 6.0 ± 2.6 mg/L higher TBOD5 and 12.4 ± 5.2 mg/L higher TSS. Further, 16S rRNA gene sequencing identified high levels of Thiothrix in the bioaugmented train, whereas TSS data between the trains diverged. This provided evidence that the significant difference in BOD and TSS was likely due to a microbial community dominated by a filamentous bacterial bloom rather than bioaugmentation.

Poly- and perfluoroalkyl substances (PFAS), commonly known as "forever chemicals," are highly persistent environmental contaminants widely present in municipal wastewater due to their extensive use in consumer products and industrial applications. This study quantitatively tracks PFAS occurrence, transformation, and fate across three municipal wastewater treatment plants (WWTPs A, B, and C; design capacities: 3, 0.8, and 13 MGD). Composite sampling revealed that influent ∑PFAS ranged from 186 to 365 ng/L, while effluent ∑PFAS ranged from 247 to 361 ng/L, reflecting increases of 4%-23% attributable to precursor transformation during treatment. For grab samples, influent ∑PFAS spanned 157-234 ng/L, with effluent values of 189-322 ng/L, representing site-specific variation from -13% to +25%. The total oxidizable precursor (TOP) assay results indicated substantially higher ∑PFAS due to precursor oxidation: influent values increased to 424-882 ng/L (2.1-3 times higher than target analysis) and effluent rose to 565-901 ng/L (up to 4 times higher). Sludge samples contained ∑PFAS of 3282-5324 ng/kg, an order of magnitude above aqueous samples and dominated by short-chain PFCAs (70%-85%). However, incineration demonstrated an approximate 99% reduction in PFAS content in sludge-derived ash, confirming its potential as an effective destruction method. The results thus emphasize WWTPs as secondary sources of PFAS contamination and the critical need for enhanced regulatory monitoring and advanced treatment strategies to mitigate their environmental and public health risks.

Groundwater contamination poses a growing threat to environmental quality and human health, particularly in regions affected by mining and agricultural activities. This study evaluated groundwater quality and associated carcinogenic and noncarcinogenic health risks in coal mining regions of Pakistan. We quantified bacterial contamination (nutrient and MacConkey agars), physicochemical properties (pH, temperature, EC, and TDS), heavy metals (Cd, Cr, Ni, Pb, Cu, and Fe), and major ions (Na⁺, Mg²⁺, Cl^-, F^-, SO₄ ^2-, and NO₃ ^-); benchmarked values against WHO limits; and estimated health risk exposure using EDD, THQ, HI, and cancer risk (CR/TCR) for adults and children. Widespread bacterial growth was detected. EC, temperature, Cd, Cr, Ni, Pb, Na⁺, SO₄ ^2-, Cl^-, and NO₃ ^- varied significantly across sites, and several parameters (Cd, Pb, Cr, Fe, NO₃ ^-, SO₄ ^2-, Na⁺, TDS, and temperature) exceeded WHO guidelines. Correlation analysis showed strong positive associations among several metals and ions. Noncarcinogenic risk exceeded safety thresholds (HI: adults 4.85-8.01; children 7.76-10.95). Carcinogenic risk from Cd, Cr, and Pb surpassed acceptable levels (TCR: adults 1.06 × 10^-3-2.19 × 10^-3; children 2.16 × 10^-3-4.49 × 10^-3). Groundwater is chemically and microbially compromised, posing unacceptable risks particularly to children necessitating urgent monitoring and mitigation.