Browsing by Author "Claveau, Leila"

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    Automated Drinking Water Quality Assessment: New Insights into Flow Cytometry Fluorescent Fingerprinting without Cell Gating
    (Cranfield University, 2024-02-16 09:05) Hassard, Francis; Claveau, Leila; Jeffrey, Paul
    Dataset for peer review paper from EngD EPSRC funded thesis L. Claveau - Chapter 2 and Chapter 3
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    From source to tap: tracking of drinking water bacteria using flow cytometry
    (Cranfield University, 2024-04) Claveau, Leila; Hassard, Francis; Jeffrey, Paul
    Understanding how water microbial quality changes occur in distributed water is crucial for ensuring water quality, safeguarding public health, optimizing treatment processes, and predicting the impacts of environmental and anthropogenic changes on microbial ecosystems. However, current monitoring tools, such as heterotrophic plate count, have limitations due to their inability to capture the full diversity of microbial communities, low sensitivity to non- culturable microorganisms, and delayed results that hinder real-time decision- making. Flow Cytometry (FCM) has emerged as a promising alternative offering high- throughput and real-time analysis of microbial cells. Through metrics such as Total Cell Count (TCC), Intact Cell Count (ICC)High Nucleic Acids (HNA), Low Nucleic Acids (LNA), and Bray and Curtis Dissimilarity Index (BCDI) resulting from the CHIC analysis of cell’s fluorescence histogram, FCM provides valuable insights into microbial abundance, viability, and metabolic activity. Despite its potential, the application of these metrics lacks standardised guidance, with metrics such as HNA and LNA not fully comprehended leading to risks of incorrect application potentially resulting in misinterpretation of water quality data and suboptimal treatment decisions. Therefore, there is a need for addressing the research question of how to appropriately use these metrics to monitor water microbial quality. This EngD study aimed to address this gap by identifying the conditions under which the FCM metrics are most valuable and evaluating their potential as early warning indicators for unwanted water microbial quality. A mixed-methods approach was employed, combining the monitoring of 35 Water Treatment Works (WTW)s and 231 associated Service Reservoirs (SR) with in-depth interstage monitoring of one individual WTW. The first case evaluated the relevance of the metrics across different WTW designs, while the second focused on their relevance at different treatment process stages within a single WTW. The findings revealed that cell counts are most effective in high-cell environments, BCDI is particularly useful in low-cell ones, and HNA/LNA metrics are most relevant in treatment stages involving chemicals. These results highlight the need for a standardised framework to guide FCM users in selecting and interpreting metrics to prevent misinterpretations and support effective water quality management.
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    Linking bioavailability and toxicity changes of complex chemicals mixture to support decision making for remediation endpoint of contaminated soils
    (Elsevier, 2018-09-27) Cipullo, Sabrina; Negrin, I.; Claveau, Leila; Snapir, Boris; Tardif, S.; Pulleyblank, C.; Prpich, George; Campo Moreno, Pablo; Coulon, Frederic
    A six-month laboratory scale study was carried out to investigate the effect of biochar and compost amendments on complex chemical mixtures of tar, heavy metals and metalloids in two genuine contaminated soils. An integrated approach, where organic and inorganic contaminants bioavailability and distribution changes, along with a range of microbiological indicators and ecotoxicological bioassays, was used to provide multiple lines of evidence to support the risk characterisation and assess the remediation end-point. Both compost and biochar amendment (p = 0.005) as well as incubation time (p = 0.001) significantly affected the total and bioavailable concentrations of the total petroleum hydrocarbons (TPH) in the two soils. Specifically, TPH concentration decreased by 46% and 30% in Soil 1 and Soil 2 amended with compost. These decreases were accompanied by a reduction of 78% (Soil 1) and 6% (Soil 2) of the bioavailable hydrocarbons and the most significant decrease was observed for the medium to long chain aliphatic compounds (EC16–35) and medium molecular weight aromatic compounds (EC16–21). Compost amendment enhanced the degradation of both the aliphatic and aromatic fractions in the two soils, while biochar contributed to lock the hydrocarbons in the contaminated soils. Neither compost nor biochar affected the distribution and behaviour of the heavy metals (HM) and metalloids in the different soil phases, suggesting that the co-presence of heavy metals and metalloids posed a low risk. Strong negative correlations were observed between the bioavailable hydrocarbon fractions and the ecotoxicological assays suggesting that when bioavailable concentrations decreased, the toxicity also decreased. This study showed that adopting a combined diagnostic approach can significantly help to identify optimal remediation strategies and contribute to change the over-conservative nature of the current risk assessments thus reducing the costs associated with remediation endpoint.
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    Microbial water quality investigation through flow cytometry fingerprinting: from source to tap
    (Oxford University Press, 2024-01-01) Claveau, Leila; Hudson, Neil; Jarvis, Peter; Jeffrey, Paul; Hassard, Francis
    Ensuring the quality of treated drinking water is crucial for preventing potential health impacts, regulatory fines, and reputation damage. Traditional culture-based microbiological methods often fail to capture the heterogeneity of the bacterial communities in drinking water. This study employed daily interstage monitoring and flow cytometry (FCM) analysis over a period of one year to investigate the dynamics of water treatment processes and service reservoirs. The objective of this study was to test the utility of FCM fingerprints for aiding in microbial event detection. We found that the chlorine concentration contact time was pivotal for microbial log reduction across the treatment works. FCM fingerprints exhibited significant deviations during operational events, such as process interruptions, but did not correlate with the presence of bacterial indicator organisms in the distributed and tap water. Furthermore, the diversity of bacterial fingerprints, quantified by the Bray–Curtis dissimilarity index, served as an indicator for identifying potentially poor microbial water quality. In chlorinated waters with low cell counts, the background signal shows potential as a metric to differentiate between different water sources, thereby offering the possibility to characterize breakthrough events in these circumstances that challenge most other microbial analytical methods. Interestingly, groundwater from simpler treatment works showed a higher occurrence of bacterial indicators, whereas surface water works had a lower incidence. These findings underpin the importance of appropriate disinfection even for “low-risk” source waters and the added value that the statistical interpretation of FCM data can offer objective decision making.
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    To gate or not to gate: revisiting drinking water microbial assessment through flow cytometry fingerprinting
    (Elsevier, 2024-02-20) Claveau, Leila; Hudson, Neil; Jeffrey, Paul; Hassard, Francis
    Flow cytometry has been utilized for over a decade as a rapid and reproducible approach to assessing microbial quality of drinking water. However, the need for specialized expertise in gating—a fundamental strategy for distinguishing cell populations—introduces the potential for human error and obstructs the standardization of methods. This work conducts a comprehensive analysis of various gating approaches applied to flow cytometric scatter plots, using a dataset spanning a year. A sensitivity analysis is carried out to examine the impact of different gating strategies on final cell count results. The findings show that dynamic gating, which requires user intervention, is essential for the analysis of highly variable raw waters and distributed water. In contrast, static gating proved suitable for more stable water sources, interstage sample locations, and water presenting a particularly low cell count. Our conclusions suggest that cell count analysis should be supplemented with fluorescence fingerprinting to gain a more complete understanding of the variability in microbial populations within drinking water supplies. Establishing dynamic baselines for each water type in FCM monitoring studies is essential for choosing the correct gating strategy. FCM fingerprinting offers a dynamic approach to quantify treatment processes, enabling options for much better monitoring and control. This study offers new insights into the vagaries of various flow cytometry gating strategies, thereby substantially contributing to best practices in the water industry. The findings foster more efficient and reliable water analysis, improving of standardizing methods in microbial water quality assessment using FCM.