3 Natural Attenuation of Pharmaceuticals in the Aquatic …
67
physicochemical transformation (Sammartino et al. 2008) and direct and indirect
phototransformation (Chianese et al. 2017; Zhang et al. 2008a, b; Kumar et al. 2019b,
c).
The nature of surface water and sediments can determine the extent and type
of natural attenuation processes that can occur. For instance, some pharmaceutical
contaminants were reported to have a higher affinity for the cationic organic matter
of a clay soil compared to the anionic organic matter from a sandy soil (Dordio et al.
2007). Chemical reactions, including the formation of complexes with various cations
(e.g., Ca
2+ ) from aquatic organic matter and tetracycline, has also been reported
(Kemper 2008). Many pharmaceuticals, such as carbamazepine, are reported to be
fairly persistent in the environment owing to their complex chemistry. Hence, the
concentration of pharmaceuticals, such as carbamazepine, is expected to be similar
in the influent and effluent of WWTPs and downstream of the receiving water body
(Ashton et al. 2004; Hernando et al. 2006). On the other hand, diclofenac, which
is a very popular over-the-counter NSAID, undergoes rapid phototransformation,
although it is resistant to biodegradation. Additionally, some pharmaceuticals may
undergo incomplete or partial biotransformation, leading to the formation of more
toxic and harmful by-products.
Natural action in rivers incidentally can attenuate pharmaceuticals to a great extent
and may thus improve the water quality. However, it may be noted that such attenuation systems work best when non-point source discharges into the river are minimal,
and the river has an ample influx of clean and unpolluted run-off (Gurr and Reinhard
2006). A better understanding of the natural attenuation processes can indicate the
time frame for the natural improvement of surface water quantity. Surface water bodies, of improved water quality, may serve as a useful source for indirect potable reuse
(Gurr and Reinhard 2006). Lin et al. (2006b) established that over a distance of 10 km,
alkylphenol (AP) ethoxylate metabolites and pharmaceuticals underwent significant
attenuation via natural processes such as phototransformation (67–100%). The river
water quality and climatic conditions may influence the time required and extent of
removal of pharmaceuticals for surface water through natural attenuation processes.
Natural attenuation processes include hydrolysis, volatilization, sorption, biotransformation, and phototransformation (Gurr and Reinhard 2006; Lin et al. 2006a). The
contribution of each of these processes may vary from river to river and from one
pharmaceutical to another. The current review aims to understand the mechanisms
governing these attenuation processes and to evaluate the physicochemical properties of various pharmaceuticals vis-à-vis their susceptibility to natural attenuation in
surface waters. Finally, the review tries to evaluate the potential of natural attenuation
processes for removal of pharmaceuticals from surface water.
67
physicochemical transformation (Sammartino et al. 2008) and direct and indirect
phototransformation (Chianese et al. 2017; Zhang et al. 2008a, b; Kumar et al. 2019b,
c).
The nature of surface water and sediments can determine the extent and type
of natural attenuation processes that can occur. For instance, some pharmaceutical
contaminants were reported to have a higher affinity for the cationic organic matter
of a clay soil compared to the anionic organic matter from a sandy soil (Dordio et al.
2007). Chemical reactions, including the formation of complexes with various cations
(e.g., Ca
2+ ) from aquatic organic matter and tetracycline, has also been reported
(Kemper 2008). Many pharmaceuticals, such as carbamazepine, are reported to be
fairly persistent in the environment owing to their complex chemistry. Hence, the
concentration of pharmaceuticals, such as carbamazepine, is expected to be similar
in the influent and effluent of WWTPs and downstream of the receiving water body
(Ashton et al. 2004; Hernando et al. 2006). On the other hand, diclofenac, which
is a very popular over-the-counter NSAID, undergoes rapid phototransformation,
although it is resistant to biodegradation. Additionally, some pharmaceuticals may
undergo incomplete or partial biotransformation, leading to the formation of more
toxic and harmful by-products.
Natural action in rivers incidentally can attenuate pharmaceuticals to a great extent
and may thus improve the water quality. However, it may be noted that such attenuation systems work best when non-point source discharges into the river are minimal,
and the river has an ample influx of clean and unpolluted run-off (Gurr and Reinhard
2006). A better understanding of the natural attenuation processes can indicate the
time frame for the natural improvement of surface water quantity. Surface water bodies, of improved water quality, may serve as a useful source for indirect potable reuse
(Gurr and Reinhard 2006). Lin et al. (2006b) established that over a distance of 10 km,
alkylphenol (AP) ethoxylate metabolites and pharmaceuticals underwent significant
attenuation via natural processes such as phototransformation (67–100%). The river
water quality and climatic conditions may influence the time required and extent of
removal of pharmaceuticals for surface water through natural attenuation processes.
Natural attenuation processes include hydrolysis, volatilization, sorption, biotransformation, and phototransformation (Gurr and Reinhard 2006; Lin et al. 2006a). The
contribution of each of these processes may vary from river to river and from one
pharmaceutical to another. The current review aims to understand the mechanisms
governing these attenuation processes and to evaluate the physicochemical properties of various pharmaceuticals vis-à-vis their susceptibility to natural attenuation in
surface waters. Finally, the review tries to evaluate the potential of natural attenuation
processes for removal of pharmaceuticals from surface water.