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Title: Influence of the microbial community structure and operational parameters on the degradation of estrogens in activated sludge processes
Author: Coello García, Tamara
ISNI:       0000 0004 7961 0302
Awarding Body: Newcastle University
Current Institution: University of Newcastle upon Tyne
Date of Award: 2018
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Prospective European legislation on β-estradiol (E2) and α-ethynylestradiol (EE2) is placing increasing pressure on the wastewater industry, who fear advanced treatment options are the only feasible way to remove estrogens from wastewater. However, little is known about factors affecting biological degradation of estrogens in conventional activated sludge systems (ASPs) and whether there is potential to optimize them. This thesis investigated the limits of ASPs to degrade natural and synthetic estrogens from two perspectives i) the hydraulic performance of reactors and ii) the α-diversity of the microbial community within ASPs. The results show that only modest changes in the hydraulics of the reactors could translate into tangible improvements in flow patterns, and it was estimated that such modifications could be sufficient to reduce effluent concentrations of E2 (23.2 L∙gVSS-1∙d-1 < kbio < 210 L∙gVSS-1∙d-1) to below prospective environmental quality standards (EQS), while EE2 (0.3 L∙gVSS-1∙d-1 < kbio < 2.9 L∙gVSS-1∙d-1) would have to rely on river dilution for compliance. Regarding estrone (E1) and estriol (E3), with no prospective legislation, the modifications would place E3 (9.9 L∙gVSS-1∙d-1 < kbio < 39.5 L∙gVSS-1∙d-1) effluent concentrations easily below its predicted no-effect concentrations (PNEC) while for E1, (2.6 L∙gVSS-1∙d-1 < kbio < 19.2 L∙gVSS-1∙d-1) it would very much depend on the degradation rates of the specific WWTP. Full-scale studies showed that both diversity and evenness were strongly associated to the degradation rates of the most recalcitrant estrogens, EE2 and E1 (p < 0.05), but not to the most easily degradable ones, E2 and E3. This suggests that EE2 and E1 degraders might be either one or a few specialist taxa or a compendium of taxa that collaborate, while E2 and E3 might be degraded by several generalist taxa. Lab-scale experiments showed that enhanced degradation of E1 degradation was associated to higher solids retention times (SRT), suggesting SRT might select for more efficient estrogen degraders. This research contributes to a better understanding of principles underlying estrogen biodegradation and its variation in ASPs, and concludes that simple changes in the design and operational parameters of WWTPs could enhance biological estrogen degradation and removal in WWTPs. This would alleviate the need (or reduce costs) for advanced oxidation processes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available