As shown by LC-OCD chromatograms the loss of humics followed
a similar pattern to the loss of colour and A254, confirming
that humics were responsible for the colour in the effluent.
The final chromatograms for treated effluent demonstrated the
different impact of each treatment. It was observed that the
remaining concentration of the LMW compounds in the hydrogen
peroxide-containing systems was lower than for either UVC or
VUV irradiation alone as longer UV exposure and higher oxidant
dose degraded the intermediate and more resistant LMW compounds.
Even though UV and VUV irradiation seemed to behave
similarly on addition of 16 mg/L H2O2 with regard to loss of colour,
A254 and DOC, the LC-OCD chromatograms for the samples after
120 min treatment (Fig. 5b) showed greater degradation of the humics, accompanied by lower concentration of the LMW compounds
for the VUV systems, due to the in situ generation of HO•
following the depletion of H2O2 after 30 min. The smaller intermediate
products generated from the breakdown of the humic matter,
such as aldehydes and carboxylic acids, are more biodegradable
than the parent compounds [10]. For UVC, the increase in biodegradation
with increasing irradiation was inversely proportional to
the loss of A254. However, in the systems where hydroxyl radicals
were present, this relationship was valid only up to a point at
which increasing exposure time led to a relative decrease in formation
of BDOC compared with mineralisation. The hydroxyl radicals,
which primarily attacked the larger molecules, would also oxidise
the smaller more biodegradable DOC reducing the fraction available
for biodegradation. Hence, integration of UV-based treatment
with a downstream biological unit may result in enhanced effectiveness
for overall treatment performance (in terms of both colour
and DOC removal) as it would enable the removal of the biodegradable
intermediates. It would also reduce the energy required for
irradiation.
As shown by LC-OCD chromatograms the loss of humics followed
a similar pattern to the loss of colour and A254, confirming
that humics were responsible for the colour in the effluent.
The final chromatograms for treated effluent demonstrated the
different impact of each treatment. It was observed that the
remaining concentration of the LMW compounds in the hydrogen
peroxide-containing systems was lower than for either UVC or
VUV irradiation alone as longer UV exposure and higher oxidant
dose degraded the intermediate and more resistant LMW compounds.
Even though UV and VUV irradiation seemed to behave
similarly on addition of 16 mg/L H2O2 with regard to loss of colour,
A254 and DOC, the LC-OCD chromatograms for the samples after
120 min treatment (Fig. 5b) showed greater degradation of the humics, accompanied by lower concentration of the LMW compounds
for the VUV systems, due to the in situ generation of HO•
following the depletion of H2O2 after 30 min. The smaller intermediate
products generated from the breakdown of the humic matter,
such as aldehydes and carboxylic acids, are more biodegradable
than the parent compounds [10]. For UVC, the increase in biodegradation
with increasing irradiation was inversely proportional to
the loss of A254. However, in the systems where hydroxyl radicals
were present, this relationship was valid only up to a point at
which increasing exposure time led to a relative decrease in formation
of BDOC compared with mineralisation. The hydroxyl radicals,
which primarily attacked the larger molecules, would also oxidise
the smaller more biodegradable DOC reducing the fraction available
for biodegradation. Hence, integration of UV-based treatment
with a downstream biological unit may result in enhanced effectiveness
for overall treatment performance (in terms of both colour
and DOC removal) as it would enable the removal of the biodegradable
intermediates. It would also reduce the energy required for
irradiation.
การแปล กรุณารอสักครู่..