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Title: A biofilter process for phytoplankton removal prior to potable water treatment works : a field and laboratory study
Author: Castro-Castellon, Ana
ISNI:       0000 0004 6494 6153
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Phytoplankton blooms compromise the quality of freshwater ecosystems and the efficient processing of water by treatment works worldwide. This research aims to determine whether in-situ filamentous biofiltration processes mediated by living roots and synthetic filters as media can reduce or remove the phytoplankton loading (micro-algae and cyanobacteria) prior to a potable water treatment works intake. The underlying biofiltration mechanisms were investigated using field and laboratory studies. A novel macroscale biofilter with three plant species, named the "Living-Filter", installed in Farmoor II reservoir, UK, was surveyed weekly for physicochemical and biological variables under continuous flow conditions during 17 weeks. The efficiency of a mesoscale biofilter using the aquatic plant Phalaris arundinacea and synthetic filters, was tested with Microcystis aeruginosa under continuous flow conditions and in batch experiments. The 'simultaneous allelochemical method' was developed for quantifying allelochemicals from Phalaris in aqueous samples. Microscale studies were used to investigate biofilter allelochemical release in response to environmental stressors and Microcystis growth inhibition in filtered and unfiltered aqueous root exudate. Results demonstrate that the removal of phytoplankton biomass by physical mechanisms has a removal efficiency of ≤45% in the "Living-Filter" (filamentous biofilter plus synthetic fabric) and that the removal of Microcystis biomass using only biofilters was 25%. Chemical mechanisms that reduce Microcystis cell numbers are mediated by allelochemicals released from biofilter roots. Root exudate treatments on Microcystis revealed that Microcystis growth is inhibited by allelochemicals, not by nutrient competition, and that protists and invertebrates play a role in removing Microcystis. Filamentous biofilters can remove phytoplankton biomass by physical, chemical and biological mechanisms. Biofilters and synthetic filters in combination improve removal efficiency. Application of macroscale biofilters prior to potable water treatment works benefits the ecosystem. Plant properties, biofilter size to surface water ratio, and retention time must be considered to maximise the benefits of biofiltration processes.
Supervisor: Hughes, Jocelyne ; Hankins, Nicholas Sponsor: Thames Water Utilites Limited
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Macro- ; meso- and microscale experiments ; Eutrophication of drinking water reservoirs: drivers ; consequences and remediation ; Field experiment ; Biofilters processes ; Biomanipulation ; HPLC method for allelochemical quantification ; Algal blooms--Management ; Allelopathy and allelochemicals ; Floating treatment wetland ; Potable water treatment processes ; Mesocosm ; Phalaris arundinacea ; Microcystis ; HPLC ; Biofilter ; Continuous flow ; Macrocosm ; Allelochemicals ; Living-Filter ; Phytoplankton removal ; Batch experiments ; Reed bed ; Algal control ; Root exudate ; Microcosm