Agriculture Reference
In-Depth Information
12.5.4 Antibiotics Pollution in Aquaculture Wastewater
As natural, synthetic, or semisynthetic compounds that are resistant to microbial
activity, antibiotics are widely used as antimicrobial agents to treat infectious
diseases in humans and animals. In 2002, the quantity of antibiotics used annually
worldwide was reported to be about 10-20 million tons. Livestock industry is an
important source of antibiotic contamination. Among the many uses of antibiotics,
about half of the total amount of antibiotics is employed in livestock. In many
countries around the world, antibiotics are widely used for the prevention and
treatment of animal diseases or added to the feed as a growth promoter. Currently,
in almost all regions around the world, antibiotics are being used to achieve high
production and economic efficiency. Antibiotics misuse in aquaculture animals
may induce the production of drug-resistant genes, and a vast majority of oral
antibiotics are directly excreted from the body of the livestock without absorption
or metabolism. As animal waste contains large amounts of nutrients, such as N, P,
etc., which are required for plant growth and generally used as fertilizer in agri-
culture, antibiotics may migrate to the soil and surface water, ultimately get
absorbed by crops, and enter the food chain, posing a potential threat to animals
and humans.
Currently, swine wastewater treatment technology mainly focuses on the
removal of N, P, COD, and other conventional pollutants and pays less attention
to the removal of antibiotics, heavy metals, and other trace contaminants. To date,
there are no qualified indicators to determine the concentrations of antibiotics in
wastewater. As even low concentrations of antibiotics in wastewater can pose a
potential threat to the environment, the development of technologies to effectively
treat and remove antibiotics from wastewater is gradually becoming a hot topic.
Zhou et al. (
2006
) used ABR to remove chlortetracycline and achieved a
removal rate of only 25-31 %. Furthermore, the removal rate of sulfamethoxazole
(SMX) by using the SBR was reported to be 66-91 %, and the removal performance
and sludge retention time were noted to have a direct relationship. Owing to the
differences in the structure and properties of antibiotics, their migration and trans-
formation behaviors in biological treatment are different. Recently, studies on the
degradation behavior of antibiotics in the activated sludge process were carried out,
which showed that some lipophilic antibiotics are likely to get adsorbed onto the
solid phase of the activated sludge, despite being subjected to degradation. Further-
more, it was reported that reduction of some antibiotics such as tetracycline
(TC) may be mainly based on the adsorption behavior, instead of biodegradation.
In addition, some studies demonstrated that biological treatment process cannot
achieve complete removal of most of the antibiotics.
