He et al. [6] reported 17 mgL
À1 of ibuprofen and 2 mgL
À1 for propiphenazone as
the highest and lowest concentrations, respectively, with respect to the other nineteen NSAIDs found in water samples, taken from six drinking water purification
plants and two water purification plants in Japan. Among all detectable NSAIDs in
the environment, diclofenac and ibuprofen often showed the highest concentration
and detection rates [6].
3 Mechanisms of Elimination of NSAIDs and Influence
Variables
The elimination of NSAIDs can occur through various mechanisms in the activated
sludge process, mainly by biodegradation, sorption, or volatilization [23]. Sewage
sludge is designed to substantially degrade the organic compounds by microbial
metabolism, which varies depending on operating conditions such as sludge retention time (SRT), hydraulic retention time (HRT), and temperature [16]. Longer
HRTs involve mayor contact time between the activated sludge and organic compounds and thus better removal efficiency [24, 25]. Sorption onto sludge, referring to
hydrophobic or electrostatic interactions with the biomass, is a common mechanism
whose effectiveness depends on the physicochemical properties of the compounds
and the biomass concentration [13]. Adsorption to the sludge of hydrophilic compounds is limited [26], and, consequently, their removal by sorption processes is
inefficient and can impede the biodegradation of these compounds too [27].
The adsorption process also intervenes in operating conditions in the NSAID
retention processes (e.g., temperature, pH, ionic strength, or porous characteristics of
the adsorbent and aqueous matrix) [28]. As well, the physicochemical properties of
NSAIDs interfere with the adsorption process. The NSAIDs are weak organic acids
with a carboxylate moiety present in them [29, 30]. Their acid dissociation constants
(pKa) range from 4.00 to 4.91, while their octanol-water partition coefficients (Kow)
range from 1.10 to 3.97, implying that NSAIDs exist as dissolved neutral species
under normal environmental conditions [31, 32]. Their high water solubility and
polar nature lead to difficulty in their removal efficiency in wastewater treatment
plants [33, 34]. The physicochemical properties relevant to their existence in water
bodies are given in Table 2.
4 Filtration Method
The filtration method using membranes as removal material has revolutionized the
remotion of emerging contaminant from wastewater. Qurie et al. [36] reported in
2014 the combined use of membranes with adsorbent compounds had resulted as an
efficient method for remotion of nonsteroidal anti-inflammatory drugs (NSAIDs);
Use of Membrane for Removal of Nonsteroidal Anti-inflammatory Drugs
265
À1 of ibuprofen and 2 mgL
À1 for propiphenazone as
the highest and lowest concentrations, respectively, with respect to the other nineteen NSAIDs found in water samples, taken from six drinking water purification
plants and two water purification plants in Japan. Among all detectable NSAIDs in
the environment, diclofenac and ibuprofen often showed the highest concentration
and detection rates [6].
3 Mechanisms of Elimination of NSAIDs and Influence
Variables
The elimination of NSAIDs can occur through various mechanisms in the activated
sludge process, mainly by biodegradation, sorption, or volatilization [23]. Sewage
sludge is designed to substantially degrade the organic compounds by microbial
metabolism, which varies depending on operating conditions such as sludge retention time (SRT), hydraulic retention time (HRT), and temperature [16]. Longer
HRTs involve mayor contact time between the activated sludge and organic compounds and thus better removal efficiency [24, 25]. Sorption onto sludge, referring to
hydrophobic or electrostatic interactions with the biomass, is a common mechanism
whose effectiveness depends on the physicochemical properties of the compounds
and the biomass concentration [13]. Adsorption to the sludge of hydrophilic compounds is limited [26], and, consequently, their removal by sorption processes is
inefficient and can impede the biodegradation of these compounds too [27].
The adsorption process also intervenes in operating conditions in the NSAID
retention processes (e.g., temperature, pH, ionic strength, or porous characteristics of
the adsorbent and aqueous matrix) [28]. As well, the physicochemical properties of
NSAIDs interfere with the adsorption process. The NSAIDs are weak organic acids
with a carboxylate moiety present in them [29, 30]. Their acid dissociation constants
(pKa) range from 4.00 to 4.91, while their octanol-water partition coefficients (Kow)
range from 1.10 to 3.97, implying that NSAIDs exist as dissolved neutral species
under normal environmental conditions [31, 32]. Their high water solubility and
polar nature lead to difficulty in their removal efficiency in wastewater treatment
plants [33, 34]. The physicochemical properties relevant to their existence in water
bodies are given in Table 2.
4 Filtration Method
The filtration method using membranes as removal material has revolutionized the
remotion of emerging contaminant from wastewater. Qurie et al. [36] reported in
2014 the combined use of membranes with adsorbent compounds had resulted as an
efficient method for remotion of nonsteroidal anti-inflammatory drugs (NSAIDs);
Use of Membrane for Removal of Nonsteroidal Anti-inflammatory Drugs
265