13.2 Refractory Organic Compounds: Chlorophenols
and Antibiotics
Phenols and their derivatives are the most common and abundant pollutants in
industrial effluents such as effluents derived from chemical and petrochemical
plants, textile, paint, and pesticide factories. They are usually used as intermediates
in the synthesis of a wide range of products such as antiseptics, pesticides, dyes,
polymers, drugs, and cosmetics. Their presence in water bodies, especially
chlorophenols which are the largest group of phenols used by industry, induces a
high pollutant potential due to both their harmful effect on aquatic life and carcinogenic and mutagenic effect to humans. Moreover, it is well-known that phenols at
concentration lower than 1 μg/L alter both taste and odor of the water (GrzechulskaDamszel 2009; Michałowicz and Duda 2007; Ye et al. 2007; USEPA 2002).
The largest part of the population is exposed to very low concentrations of
chlorophenols (of the order of magnitude of parts per trillion) through drinking
water that has been subject to disinfection with chlorine. But the most exposed
persons are those who work directly with these compounds either in their manufacture or their use as pesticides. For example, in timber manufacture, a mixture of
chlorophenols is used for the preservation of wood. In this case, the major way in
which humans are exposed to chlorophenols is through the skin, when the
chlorophenols from the treatment of wood come into contact with the skin.
Chlorophenols can enter the human body by ingestion along with the food, through
dermal contact by skin absorption, or by air. They accumulate mainly in the liver and
kidneys and less in the brain, muscles, and fat (von Stackelberg 2013; White 1992).
An admissible human daily dose of 2-chlorophenol without inducing carcinogenic
effects is 5 μg/kg of body weight, while for 2,4-dichlorophenol, 2,4,6trichlorophenol, and pentachlorophenol, the dose is 3 μg/kg of body weight
(USEPA 1982).
The health effects of chlorophenols are in direct proportion with their degree of
chlorination. An acute exposure to low-phenol chlorination results in muscle
spasms, twitching, tremors, weakness, ataxia, convulsions, and collapse (White
1992). Consequently, it is necessary to have a close monitoring of them in water
bodies.
Pharmaceutical compounds have raised increasing concerns over the past years
due to their effects on the environment. Recently, such compounds like antibiotics,
analgesics, and steroids have been detected in several public water systems from the
United States of America, several European countries, and Australia. Many pharmaceutical products are used in both human and veterinary medicine and finally, are
released into the environment through metabolic processes. Typically, wastewater
treatment plants cannot completely remove these compounds, and, therefore, many
of them are discharged into the environment where they can affect the microbial
community, leading to the disruption of the natural elemental cycles (Dodson et al.
2011; Kümmerer 2009a; Wick et al. 2009; Kaniou et al. 2005).
13 Photocatalytic Degradation of Chlorophenols and Antibiotics from Wastewater
413
and Antibiotics
Phenols and their derivatives are the most common and abundant pollutants in
industrial effluents such as effluents derived from chemical and petrochemical
plants, textile, paint, and pesticide factories. They are usually used as intermediates
in the synthesis of a wide range of products such as antiseptics, pesticides, dyes,
polymers, drugs, and cosmetics. Their presence in water bodies, especially
chlorophenols which are the largest group of phenols used by industry, induces a
high pollutant potential due to both their harmful effect on aquatic life and carcinogenic and mutagenic effect to humans. Moreover, it is well-known that phenols at
concentration lower than 1 μg/L alter both taste and odor of the water (GrzechulskaDamszel 2009; Michałowicz and Duda 2007; Ye et al. 2007; USEPA 2002).
The largest part of the population is exposed to very low concentrations of
chlorophenols (of the order of magnitude of parts per trillion) through drinking
water that has been subject to disinfection with chlorine. But the most exposed
persons are those who work directly with these compounds either in their manufacture or their use as pesticides. For example, in timber manufacture, a mixture of
chlorophenols is used for the preservation of wood. In this case, the major way in
which humans are exposed to chlorophenols is through the skin, when the
chlorophenols from the treatment of wood come into contact with the skin.
Chlorophenols can enter the human body by ingestion along with the food, through
dermal contact by skin absorption, or by air. They accumulate mainly in the liver and
kidneys and less in the brain, muscles, and fat (von Stackelberg 2013; White 1992).
An admissible human daily dose of 2-chlorophenol without inducing carcinogenic
effects is 5 μg/kg of body weight, while for 2,4-dichlorophenol, 2,4,6trichlorophenol, and pentachlorophenol, the dose is 3 μg/kg of body weight
(USEPA 1982).
The health effects of chlorophenols are in direct proportion with their degree of
chlorination. An acute exposure to low-phenol chlorination results in muscle
spasms, twitching, tremors, weakness, ataxia, convulsions, and collapse (White
1992). Consequently, it is necessary to have a close monitoring of them in water
bodies.
Pharmaceutical compounds have raised increasing concerns over the past years
due to their effects on the environment. Recently, such compounds like antibiotics,
analgesics, and steroids have been detected in several public water systems from the
United States of America, several European countries, and Australia. Many pharmaceutical products are used in both human and veterinary medicine and finally, are
released into the environment through metabolic processes. Typically, wastewater
treatment plants cannot completely remove these compounds, and, therefore, many
of them are discharged into the environment where they can affect the microbial
community, leading to the disruption of the natural elemental cycles (Dodson et al.
2011; Kümmerer 2009a; Wick et al. 2009; Kaniou et al. 2005).
13 Photocatalytic Degradation of Chlorophenols and Antibiotics from Wastewater
413