Abstract:
increases in
coagulant required to remove sufficient quantities of natural organic matter
(NOM) to ensure compliance with trihalomethane (THM) regulations lead to an
increase in the volume of potable sludge generated. Here options to treat the sludge or
reduce the amount of
sludge produced are assessed. The results from assessing
advanced oxidation processes for the treatment of potable sludge showed that although
feasible it would be more
advantageous to remove the NOM from the water via a
process that generates less sludge. For the removal of NOM the main focus was on the
adsorption of NOM onto TiO2 powder and this was optimised in terms of the removal of
bulk water
parameters, namely dissolved organic carbon (DOC) and ultraviolet (UV)
absorbance at 254 m
(UV254). The results showed that both the DOC and UV254
absorbance could be reduced
by over 90%. Secondly the immobilisation of TiO2 as a
thin lm coated on a
supporting substrate was evaluated. To obtain a uniform coating
was
complex and the NOM removal was much poorer than that achieved using the TiO2
powder due to the reduced surface area. To overcome the complex issue of separating
the TiO2 powder from the treated water larger pellets sized TiO2 particles were used as
a adsorbent
coupled with side-stream UV regeneration. Results from both bench and
pilot scales showed that the DOC concentration could be reduced by 86% and the UV254
absorbance
by 75%. In addition low M compounds which are untouched by
conventional
coagulation were removed. Combining NOM adsorption onto TiO2 pellets
with ferric
coagulation increased the reduction in UV254 absorbance to 94% at a reduced
coagulant dose. This reduction in coagulant dose of over 80% will have a major impact
on the volume of potable sludge generated.
