2.2.1 Ozonation
Ozonation process involves two reaction mechanisms: (1) direct reaction by ozone
and (2) indirect reaction by OH radicals during ozone reactions [64]. While ozone
reacts selectively with electron-rich moieties compounds, the OH radicals can react
with a wide range of aromatic compounds including NSAIDs [65]. Regardless of the
reaction mechanisms, the required ozone treatment dose is proportional to the bulk
organic content in the wastewater. Ozone (O 3 ) has been shown to degrade trace
organic contaminants during wastewater treatment and water reuse applications
[44, 66]. Ozone reacts with TrOC either through direct reactions or through the
formation of free radicals, including the hydroxyl radical (
•
OH) [67]. Oxidation
using ozone can achieve >92% removal of a number of pharmaceuticals, including
NSAIDs, and pesticides such as ofloxacin, sulfamethoxazole, propranolol, carbamazepine, clofibric acid, diclofenac, atrazine, and diuron [59, 63, 68]. However, a
number of other pharmaceuticals and personal care products (e.g., ibuprofen,
naproxen, caffeine, and tonalide) could not be oxidized using the same process [63].
2.2.2 UV Oxidation
UV oxidation generates hydroxyl radicals by photolysis. Huber et al. demonstrated
that UV treatment alone resulted in 75, 13, and 7% removal of diclofenac,
iopromide, and sulfamethoxazole, respectively. Complete removal of several pharmaceuticals (e.g., ofloxacin, sulfamethoxazole, propranolol, carbamazepine,
clofibric acid, and diclofenac) was achieved using the combination of hydrogen
peroxide and UV radiation [59], although only 30–40% of ibuprofen, diphenhydramine, phenazone, and phenytoin could be removed using this method [69].
The AOPs are effective at treating NSAIDs, but the operating cost of AOPs is
high due to the requirements in chemicals and energy [70]. It therefore limits their
applications as a widespread solution of NSAID remediation.
2.3 Membrane Separation Process
High-pressure membrane filtration, including nanofiltration (NF) and reverse osmosis (RO), has been widely used to remove organic pollutants including NSAIDs [71–
75]. NF/RO membranes can reject TrOCs mainly due to size exclusion, electrostatic
exclusion, and adsorption on the membrane [76, 77]. In a full-scale study, Verliefde
et al. [78] reported a high rejection (>95%) of most investigated NSAIDs by the
Triseps (X20 and ACM5) and Hydranautics (ESPA1 and ESPA4) RO membranes.
In another study, an NF-270 membrane achieved a high rate of rejection for charged
pharmaceuticals, i.e., 96% for ibuprofen, where removal of NSAIDs was enhanced
Contemporary Methods for Removal of Nonsteroidal Anti-inflammatory Drugs in. . .
227
Ozonation process involves two reaction mechanisms: (1) direct reaction by ozone
and (2) indirect reaction by OH radicals during ozone reactions [64]. While ozone
reacts selectively with electron-rich moieties compounds, the OH radicals can react
with a wide range of aromatic compounds including NSAIDs [65]. Regardless of the
reaction mechanisms, the required ozone treatment dose is proportional to the bulk
organic content in the wastewater. Ozone (O 3 ) has been shown to degrade trace
organic contaminants during wastewater treatment and water reuse applications
[44, 66]. Ozone reacts with TrOC either through direct reactions or through the
formation of free radicals, including the hydroxyl radical (
•
OH) [67]. Oxidation
using ozone can achieve >92% removal of a number of pharmaceuticals, including
NSAIDs, and pesticides such as ofloxacin, sulfamethoxazole, propranolol, carbamazepine, clofibric acid, diclofenac, atrazine, and diuron [59, 63, 68]. However, a
number of other pharmaceuticals and personal care products (e.g., ibuprofen,
naproxen, caffeine, and tonalide) could not be oxidized using the same process [63].
2.2.2 UV Oxidation
UV oxidation generates hydroxyl radicals by photolysis. Huber et al. demonstrated
that UV treatment alone resulted in 75, 13, and 7% removal of diclofenac,
iopromide, and sulfamethoxazole, respectively. Complete removal of several pharmaceuticals (e.g., ofloxacin, sulfamethoxazole, propranolol, carbamazepine,
clofibric acid, and diclofenac) was achieved using the combination of hydrogen
peroxide and UV radiation [59], although only 30–40% of ibuprofen, diphenhydramine, phenazone, and phenytoin could be removed using this method [69].
The AOPs are effective at treating NSAIDs, but the operating cost of AOPs is
high due to the requirements in chemicals and energy [70]. It therefore limits their
applications as a widespread solution of NSAID remediation.
2.3 Membrane Separation Process
High-pressure membrane filtration, including nanofiltration (NF) and reverse osmosis (RO), has been widely used to remove organic pollutants including NSAIDs [71–
75]. NF/RO membranes can reject TrOCs mainly due to size exclusion, electrostatic
exclusion, and adsorption on the membrane [76, 77]. In a full-scale study, Verliefde
et al. [78] reported a high rejection (>95%) of most investigated NSAIDs by the
Triseps (X20 and ACM5) and Hydranautics (ESPA1 and ESPA4) RO membranes.
In another study, an NF-270 membrane achieved a high rate of rejection for charged
pharmaceuticals, i.e., 96% for ibuprofen, where removal of NSAIDs was enhanced
Contemporary Methods for Removal of Nonsteroidal Anti-inflammatory Drugs in. . .
227