Abstract:
Seasonal periods of high rainfall and changes in land management have led to
difficulties for UK water companies to remove sufficient natural organic matter
(NOM) to stay in compliance with the tightening trihalomethane (THMs) standards.
Hence alternative treatment options have come into focus of research and
development.
The continuous anion exchange process based on a novel magnetic resin (MIEX®
resin) has emerged as a promising method to increase NOM removal and has been
compared in this thesis to the most widely spread drinking water treatment method of
coagulation with hydrolysing metal salts. Therefore the removal efficiency of both
processes was investigated by treating different natural waters sources as well as
selected organic model compounds of different hydrophobicity and molecular weight
(MW). Magnetic resin was thereby seen to be competitive with coagulation for DOC
removal in low SUVA sources dominated by mid to low MW material and to
outperform coagulation for the treatment of low MW, hydrophilic acids.
However magnetic resin had to be used in combination with subsequent coagulation
using largely reduced Fe doses to ensure high levels of DOC removal in sources
dominated by high MW NOM. This was related to a physical blockage mechanism of
the easily accessible external resin bead surface by this high MW material. An effect
that could be reduced by applying increased resin doses, which provided a larger
external surface area for DOC removal.
A combination of magnetic resin treatment with coagulation was nonetheless seen to
be able to increase DOC removal as well as to generate enhanced floc properties in
terms of strength, settling velocity and size. Beside a reduced THM formation
potential, making magnetic resin an effective tool to help meet legislative standards,
an increased solid-liquid separation was seen in pilot-scale to result from these
effects.
