Browsing by Author "Petrie, Bruce"

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    Assessing potential modifications to the activated sludge process to improve simultaneous removal of a diverse range of micropollutants
    (Elsevier Science B.V., Amsterdam., 2014-10-01T00:00:00Z) Petrie, Bruce; McAdam, Ewan J.; Lester, John N.; Cartmell, Elise
    It is proposed that wastewater treatment facilities meet legislated discharge limits for a range of micropollutants. However, the heterogeneity of these micropollutants in wastewaters make removal difficult to predict since their chemistry is so diverse. In this study, a range of organic and inorganic micropollutants known to be preferentially removed via different mechanisms were selected to challenge the activated sludge process (ASP) and determine its potential to achieve simultaneous micropollutant removal. At a fixed hydraulic retention time (HRT) of 8 h, the influence of an increase in solids retention time (SRT) on removal was evaluated. Maximum achievable micropollutant removal was recorded for all chemicals (estrogens, nonylphenolics and metals) at the highest SRT studied (27 days). Also, optimisation of HRT by extension to 24 h further augmented organic biodegradation. Most notable was the enhancement in removal of the considerably recalcitrant synthetic estrogen 17a-ethinylestradiol which increased to 65 analysis indicates that this enhanced micropollutant behaviour is ostensibly related to the concomitant reduction in food: microorganism ratio. Interestingly, extended HRT also initiated nonylphenol biodegradation which has not been consistently observed previously in real wastewaters. However, extending HRT increased the solubilisation of particulate bound metals, increasing effluent aqueous metals concentrations (i.e., 0.45± 19%. Regressionmm filtered) by > compliance. Consequently, identification of an optimum process condition for generic micropollutant removal is expected to favour a more integrated approach where upstream process unit optimisation (i.e., primary sedimentation) is demanded to reduce loading of the particle bound metal phase onto the ASP, thereby enabling longer HRT in the ASP to be considered for optimum removal of organic micropollutants.100%. This is significant as only the aqueous metal phase is to be considered for environmental
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    Enhancing the removal of a diverse range of hazardous chemicals from wastewaters
    (Cranfield University, 2014-01) Petrie, Bruce; Cartmell, Elise; McAdam, Ewan; Lester, John N.
    Due to increasingly stringent legislation covering the discharge of hazardous chemicals into the environment, existing wastewater treatment processes need to be upgraded for their removal. This thesis explores the removal of a diverse range of hazardous chemicals during secondary wastewater treatment with the overall aim of enhancing their removal simultaneously by activated sludge. Previous research in this field has made the broad comparison of full-scale activated sludge plants (ASPs) which receive varying influent sewage compositions and flow. Consequently, assessing the direct impact of process operation to hazardous chemical removal has been difficult. In this study, the independent impact of the process variables solids retention time (SRT) and hydraulic retention time (HRT) were examined using a pilot-scale ASP. To measure ASP resilience for the removal of a wide range of hazardous chemicals of varied chemistry and preferred removal pathways steroid estrogens, nonylphenolic surfactants and metals were monitored. Cont/d.
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    Influence of solids and hydraulic retention times on microbial diversity and removal of estrogens and nonylphenols in a pilot-scale activated sludge plant
    (Elsevier, 2023-08-30) Mensah, Lawson; Petrie, Bruce; Scrimshaw, Mark; Cartmell, Elise; Fletton, Mandy; Campo, Pablo
    The removal of EDCs in activated sludge processes can be enhanced by increasing solid and hydraulic retention times (SRT and HRT); it has been suggested that the improvement in removal is due to changes in microbial community structure (MCS). Though the influence of SRT and HRT on chemical removal and MCS has been studied in isolation, their synergistic impact on MCS and the removal of estrogens and nonylphenols in activated sludge remains unknown. Hence, we investigated how both parameters influence MCS in activated sludge processes and their ulterior effect on EDC removal. In our study, an activated sludge pilot-plant was fed with domestic sewage fortified with 100 and 1000 ng/L nonylphenols or 2 and 15 ng/L estrogens and operated at 3, 10 and 27 d SRT (constant HRT) and at 8, 16 and 24 h HRT (constant SRT). The MCS was assessed by phospholipid fatty acids (PLFA) analysis, and the archaeal and bacterial diversities were determined by 16S rRNA analysis. From the PLFA, the microbial abundance ranked as follows: Gram-negative > fungi > Gram-positive > actinomycetes whilst 16S rRNA analysis revealed Proteobacteria > Bacteroidetes > Others. Both PLFA and 16S rRNA analysis detected changes in MCS as SRT and HRT were increased. An SRT increment from 3 to 10 d resulted in higher estrone (E1) removal from 19 to 93% and nonylphenol-4-exthoxylate (NP4EO) from 44 to 73%. These findings demonstrate that EDC-removal in activated sludge plants can be optimised where longer SRT (>10 d) and HRT (>8 h) are suitable. We have also demonstrated that PLFA can be used for routine monitoring of changes in MCS in activated sludge plants.