Environmental Engineering Reference
In-Depth Information
of these compounds becomes dificult, as these are present at very low concentrations.
There is no regulation in the water quality standards for these contaminants. Hence, there
is no measure to monitor these compounds in the efluents of wastewater treatment plants
(WWTPs). Besides, complete information about the toxicity of these compounds is also not
available. These compounds are getting into the water through municipal sewage. A major
part of the ingested pharmaceuticals is excreted from the body and subsequently gets dis-
charged into the wastewater. Most of the conventional WWTPs are incapable of removing
these contaminants. As a result, these compounds will be present in WWTP efluent dis-
charged into the water bodies. Many a time, the towns/cities located in the downstream of
the water bodies/rivers use this water as the water source for water supply in the cities. As
a result, human beings are getting exposed to these compounds very regularly.
Emerging contaminants include endocrine-disrupting compounds (EDCs), pharmaceu-
tically active compounds (PhACs), and PCPs. PCPs are chemicals present in cosmetics,
toothpaste, sunscreens, soaps, lotions, insect repellants, etc. Parabens and phenols are
mainly present in these compounds. EDCs are the compounds that are not produced by
the body but mimic or act like natural hormones in the body. These include solvents, pesti-
cides, fungicides, pharmaceuticals, and plasticizers. Depending on the effect on the body,
EDCs are divided into estrogenic or antiestrogenic, androgenic or antiandrogenic, and
thyroid hormones. EDCs when present in very little concentrations also cause adverse
effects in the body. There have been reports indicating that EDCs in aquatic systems cause
feminization of ish, presence of intersex (neither male nor female), and increased egg pro-
duction. Sex hormones include estriol, estradiol, and estrone.
PhACs include pharmaceuticals consumed by human or animals and pharmaceutical
metabolites. These compounds can interact with biological systems through enzyme or
receptors (Comerton et al., 2009). Pharmaceuticals include analgesics, antibiotics, antihy-
perlipidemics, antiepileptic, and stimulants. Pharmaceuticals can be nonsteroidal anti-
inlammatory drugs or analgesics, which include weak acids. These are polar in nature
and contain carboxyl and hydroxyl groups. Diclofenac, ibuprofen, naproxen, paracetamol,
etc., belong to this category. Among these compounds, diclofenac showed most toxic-
ity even under concentrations <100 mg/L (Cleuvers, 2003). Blood lipid-lowering agents
include gemibrozil, cloibrate, atorvastatin, etc. They are used very widely today for
controlling cholesterol and triglycerides. Levoloxacin, ampicillin, erythromycin, sulfa-
methoxazole, tetracycline, etc., are the antibiotics detected in water bodies. Their presence
in water should be seriously considered because continuous exposure to these compounds
makes the microorganisms resistant to these drugs. Jones et al. (2002) classiied antibiotics
as extremely toxic to microorganisms and very toxic to algae. Antiepileptic drugs affect
the central nervous system by reducing neuronal activity. These compounds can be lethal
to the lower-level organisms. Carbamazepine is an antiepileptic drug that has been stud-
ied extensively. This compound is known to be carcinogenic to rats (Thacker, 2005).
Emerging contaminants in water affect the ecosystem adversely. Antibiotics in water can
cause changes in the microorganisms present in water. It can lead to antibiotic resistance
of microorganisms. Feminization of ish was reported in Northwestern Ontario, which
was the effect of EDCs such as estrone, estradiol, and nonylphenol present in the river.
In a Minnesota lake, female egg-yolk protein was found in male ish. Many cases were
reported regarding the reproductive abnormalities in aquatic systems due to the pres-
ence of emerging contaminants. The main challenges faced in the treatment of emerging
contaminants are their high solubility, high chemical stability, and low biodegradability.
These compounds will be present in very little amounts in water in the range of nano-
grams per liter, which makes the monitoring of these compounds dificult.
