Browsing by Author "Upton, Andrew"

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    Comparing flow cytometry with culture-based methods for microbial monitoring and as a diagnostic tool for assessing drinking water treatment processes
    (Elsevier, 2019-06-18) Cheswick, Ryan Ashley; Cartmell, Elise; Lee, Susan; Upton, Andrew; Weir, Paul; Moore, Graeme; Nocker, Andreas; Jefferson, Bruce; Jarvis, Peter
    Flow cytometry (FCM) and the ability to measure both total and intact cell populations through DNA staining methodologies has rapidly gained attention and consideration across the water sector in the past decade. In this study, water quality monitoring was undertaken over three years across 213 drinking water treatment works (WTW) in the Scottish Water region (Total n = 39,340). Samples subject to routine regulatory microbial analysis using culture-based methods were also analysed using FCM. In addition to final treated water, the bacterial content in raw water was measured over a one-year period. Three WTW were studied in further detail using on-site inter-stage sampling and analysis with FCM. It was demonstrated that there was no clear link between FCM data and the coliform samples taken for regulatory monitoring. The disinfectant Ct value (Ct = mg·min/L) was the driving factor in determining final water cell viability and the proportion of intact cells (intact/total cells) and the frequency of coliform detections in the water leaving the WTW. However, the free chlorine residual, without consideration of treatment time, was shown to have little impact on coliform detections or cell counts. Amongst the three treatment trains monitored in detail, the membrane filtration WTW showed the greatest log removal and robustness in terms of final water intact cell counts. Flow cytometry was shown to provide insights into the bacteriological quality of water that adds significant value over and above that provided by traditional bacterial monitoring.
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    Methods, measurements, and novel materials for improving depth filtration processes used in drinking water treatment.
    (Cranfield University, 2021-06) Upton, Andrew; Jarvis, Peter; Jefferson, Bruce
    Rapid media filtration is used to treat most surface water sources for municipal drinking water supply. This thesis presents results of an investigation into how media filters in Scottish Water, built decades ago to different standards, can meet increasingly stringent water quality requirements. A new method for efficient assessment of filter performance and diagnosis of issues using online data were developed. A recursive partitioning algorithm applied to operationally relevant predictor variables was shown to efficiently and effectively characterise the conditions associated with elevated turbidity over an extended period of operation. Tree models can then be used to communicate a diagnosis in operational terms to aid the efficient management of individual pathogen barriers in a multi-barrier system. Robust rapid filtration requires effective coagulation. An investigation was conducted at a water treatment works (WTW) to understand the influence of zeta potential. The effective zeta potential window was modelled & observed to change with conditions. The online measurement of zeta potential was shown to be useful for process optimisation by providing a quantitative measurement with a mechanistic basis for coagulation conditions. This provides advantages over jar testing which may poorly represent the system under investigation. Pilot and full-scale trials of an alternative expanded aluminosilicate media show that the additional bed expansion achieved by replacing sand with the lower density material can, at comparatively low cost, improve the performance of rapid gravity filters with a common design limitation. The effective application of new finer grade expanded aluminosilicate was shown at pilot and full scale. This thesis presents a suite of efficient solutions to ensure aging 20th century filters robustly meet challenges in 21st century. This is achieved by improving understanding of how and why specific constraints limit the performance of existing RGFs and developing strategic solutions to overcome common limitations to process performance.
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    Rapid gravity filtration operational performance assessment and diagnosis for preventative maintenance from on-line data
    (Elsevier, 2016-12-16) Upton, Andrew; Jefferson, Bruce; Jarvis, Peter
    Rapid gravity filters, the final particulate barrier in many water treatment systems, are typically monitored using on-line turbidity, flow and head loss instrumentation. Current metrics for assessing filtration performance from on-line turbidity data were critically assessed and observed not to effectively and consistently summarise the important properties of a turbidity distribution and the associated water quality risk. In the absence of a consistent risk function for turbidity in treated water, using on-line turbidity as an indicative rather than a quantitative variable appears to be more practical. Best practice suggests that filtered water turbidity should be maintained below 0.1 NTU, at higher turbidity we can be less confident of an effective particle and pathogen barrier. Based on this simple distinction filtration performance has been described in terms of reliability and resilience by characterising the likelihood, frequency and duration of turbidity spikes greater than 0.1 NTU. This view of filtration performance is then used to frame operational diagnosis of unsatisfactory performance in terms of a machine learning classification problem. Through calculation of operationally relevant predictor variables and application of the Classification and Regression Tree (CART) algorithm the conditions associated with the greatest risk of poor filtration performance can be effectively modelled and communicated in operational terms. This provides a method for an evidence based decision support which can be used to efficiently manage individual pathogen barriers in a multi-barrier system.
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    THM and HAA formation from NOM in raw and treated surface waters
    (IWA Publishing, 2017-01-29) Golea, Dan; Upton, Andrew; Jarvis, Peter; Judd, Simon J.
    The disinfection by-product (DBP) formation potential (FP) of natural organic matter (NOM) in surface water sources has been studied with reference to the key water quality determinants (WQDs) of UV absorption (UV254), colour, and dissolved organic carbon (DOC) concentration. The data set used encompassed raw and treated water sampled over a 30-month period from 30 water treatment works (WTWs) across Scotland, all employing conventional clarification. Both trihalomethane (THM) and haloacetic acid (HAA) FPs were considered. In addition to the standard bulk WQDs, the DOC content was fractionated and analysed for the hydrophobic (HPO) and hydrophilic (HPI) fractions. Results were quantified in terms of the yield (dDBPFP/dWQD) and the linear regression coefficient R2 of the yield trend. The NOM in the raw waters was found to comprise 30–84% (average 66%) of the more reactive HPO material, with this proportion falling to 18–63% (average 50%) in the treated water. Results suggested UV254 to be as good an indicator of DBPFP as DOC or HPO for the raw waters, with R2 values ranging from 0.79 to 0.82 for THMs and from 0.71 to 0.73 for HAAs for these three determinants. For treated waters the corresponding values were significantly lower at 0.52–0.67 and 0.46–0.47 respectively, reflecting the lower HPO concentration and thus UV254 absorption and commensurately reduced precision due to the limit of detection of the analytical instrument. It is concluded that fractionation offers little benefit in attempting to discern or predict chlorinated carbonaceous DBP yield for the waters across the geographical region studied. UV254 offered an adequate estimate of DBPFP based on a mean yield of ∼2600 and ∼2800 μg per cm−1 absorbance for THMFP for the raw and treated waters respectively and ∼3800 and2900 μg cm−1 for HAAFP, albeit with reduced precision for the treated waters.