The four UV-mediated systems: UVC, UVC/H2O2, VUV and
VUV/H2O2, were able to provide a high degree of decolourisation of
the secondary effluent. The systems which support the production
of hydroxyl radicals were shown to be more effective for improving
the quality of the secondary effluent compared with direct UVC
photolysis.
When the same concentration of hydrogen peroxide was added
to either the UV or VUV system, similar overall removal of organics
was observed. Doubling the dose of hydrogen peroxide with UVC irradiation led to improved, although not proportionally greater,
overall performance.
Loss of colour, DOC and fulvic acid-like compounds followed first
order kinetics. Parallel first order kinetics were able to model the
rate of loss of A254 and humic acid-like compounds for the systems
involving the production of hydroxyl radicals.
FRI analysis and size exclusion chromatography demonstrated
that the loss of colour was due to the breakdown of the high molecular
weight humic acid-like material to lower molecular weight
compounds. These lower molecular weight products were shown
to be more biodegradable, and demonstrate the applicability of a
subsequent biological treatment to further remove the DOC from
the effluent.
The addition of hydrogen peroxide makes the UV-mediated
decolourisation process more economically feasible. Overall
performance of the UV-based treatments in terms of reduction
in colour, A254, DOC (and thus EE/O) decreased in the
order: UVC/H2O2 (32 mg/L) > VUV/H2O2 (16 mg/L) > UVC/H2O2
(16 mg/L) > VUV > UVC.
The four UV-mediated systems: UVC, UVC/H2O2, VUV and
VUV/H2O2, were able to provide a high degree of decolourisation of
the secondary effluent. The systems which support the production
of hydroxyl radicals were shown to be more effective for improving
the quality of the secondary effluent compared with direct UVC
photolysis.
When the same concentration of hydrogen peroxide was added
to either the UV or VUV system, similar overall removal of organics
was observed. Doubling the dose of hydrogen peroxide with UVC irradiation led to improved, although not proportionally greater,
overall performance.
Loss of colour, DOC and fulvic acid-like compounds followed first
order kinetics. Parallel first order kinetics were able to model the
rate of loss of A254 and humic acid-like compounds for the systems
involving the production of hydroxyl radicals.
FRI analysis and size exclusion chromatography demonstrated
that the loss of colour was due to the breakdown of the high molecular
weight humic acid-like material to lower molecular weight
compounds. These lower molecular weight products were shown
to be more biodegradable, and demonstrate the applicability of a
subsequent biological treatment to further remove the DOC from
the effluent.
The addition of hydrogen peroxide makes the UV-mediated
decolourisation process more economically feasible. Overall
performance of the UV-based treatments in terms of reduction
in colour, A254, DOC (and thus EE/O) decreased in the
order: UVC/H2O2 (32 mg/L) > VUV/H2O2 (16 mg/L) > UVC/H2O2
(16 mg/L) > VUV > UVC.
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