In the second configuration, a GAC posttreatment can specifically target the
residual NSAID compounds in the MBR permeate without significant competition
or interference from the bulk organics [21]. Nevertheless, periodic regeneration/
replenishment of the activated carbon is necessary, because over an extended
operating period, fouling and substrate deterioration are inevitable.
2.4.3 Biological Treatment Coupled with Advanced Oxidation Process
Advanced oxidation processes (UV or ozonation) are very effective at oxidizing
NSAID compounds but are mostly used as a polishing or disinfection step. Packer
et al. [121] observed a rapid and mild photodegradation of diclofenac and
ketoprofen, respectively. Nguyen et al. [77] reported almost 100% removal of
pentachlorophenol and triclosan within 7.5 min of UV 254 nm exposure. These
compounds are quite recalcitrant to biological treatment. The benefit of combining
biological treatment (e.g., MBR) with UV oxidation therefore can be shown by
examining the removal of these compounds. For example, diclofenac was poorly
removed by the MBR (40%). By contrast, treatment by UV system following MBR
attained exceptionally high removal efficiency (i.e., 98%). The MBR also provides a
low background organic matter content and suspended solids-free influent which is
highly suitable as influent for UV oxidation process.
The efficiency of a combined MBR and ozonation process for NSAID removal
has been assessed in different operational modes. de Wilt et al. [122] reported the
limitation of removing ibuprofen, naproxen, and diclofenac by individual biological
and ozonation process. In details, 14 and 80% removal of diclofenac was achieved
by biological and ozonation process, respectively. However, their combination
resulted in >99% removal, indicating the complementary impact. The combination
also reduced the ozone dose due to the decrease in organic matter of the influent
[122]. Ikehata et al. [123] also reported that diclofenac was reactive toward ozone.
Apart from the MBR–ozonation, studies have reported the integrated MBR with
ozonation (i.e., ozone is dosed directly in the reactor) [124]. Positive results include
virtue of higher removal of ozonation by-products and lower ozone treatment dose
requirement. A similar observation was reported by Laera et al. [125], where the
ozonation by-product was 20-fold lower in the final effluent of the integrated process
than in that of MBR–post-ozonation process. Mascolo et al. [126] achieved a similar
removal of an antiviral drug (acyclovir) by both configurations; however, the
integrated process again was more beneficial in terms of removal of specific ozonation by-products.
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residual NSAID compounds in the MBR permeate without significant competition
or interference from the bulk organics [21]. Nevertheless, periodic regeneration/
replenishment of the activated carbon is necessary, because over an extended
operating period, fouling and substrate deterioration are inevitable.
2.4.3 Biological Treatment Coupled with Advanced Oxidation Process
Advanced oxidation processes (UV or ozonation) are very effective at oxidizing
NSAID compounds but are mostly used as a polishing or disinfection step. Packer
et al. [121] observed a rapid and mild photodegradation of diclofenac and
ketoprofen, respectively. Nguyen et al. [77] reported almost 100% removal of
pentachlorophenol and triclosan within 7.5 min of UV 254 nm exposure. These
compounds are quite recalcitrant to biological treatment. The benefit of combining
biological treatment (e.g., MBR) with UV oxidation therefore can be shown by
examining the removal of these compounds. For example, diclofenac was poorly
removed by the MBR (40%). By contrast, treatment by UV system following MBR
attained exceptionally high removal efficiency (i.e., 98%). The MBR also provides a
low background organic matter content and suspended solids-free influent which is
highly suitable as influent for UV oxidation process.
The efficiency of a combined MBR and ozonation process for NSAID removal
has been assessed in different operational modes. de Wilt et al. [122] reported the
limitation of removing ibuprofen, naproxen, and diclofenac by individual biological
and ozonation process. In details, 14 and 80% removal of diclofenac was achieved
by biological and ozonation process, respectively. However, their combination
resulted in >99% removal, indicating the complementary impact. The combination
also reduced the ozone dose due to the decrease in organic matter of the influent
[122]. Ikehata et al. [123] also reported that diclofenac was reactive toward ozone.
Apart from the MBR–ozonation, studies have reported the integrated MBR with
ozonation (i.e., ozone is dosed directly in the reactor) [124]. Positive results include
virtue of higher removal of ozonation by-products and lower ozone treatment dose
requirement. A similar observation was reported by Laera et al. [125], where the
ozonation by-product was 20-fold lower in the final effluent of the integrated process
than in that of MBR–post-ozonation process. Mascolo et al. [126] achieved a similar
removal of an antiviral drug (acyclovir) by both configurations; however, the
integrated process again was more beneficial in terms of removal of specific ozonation by-products.
232
L. N. Nguyen et al.