Bacterial resistance in sanitary sewage sludge in different treatment systems

The purpose of this paper is to assess the occurrence and risk of dispersion in the environment of antibiotic-resistant microorganisms from sanitary sewage sludge produced in two conventional wastewater treatment systems adopted in the West of the State of Paraná, Brazil.

The sludge samples were collected for three months from two wastewater treatment plants, totaling six sample points, and sent to the laboratory where the physical-chemical and biological determinations were performed.

This work made possible to find that the sludge produced in the sewage treatment plants presents potential risks related to the spread of microorganisms due to the occurrence of resistant isolates of Escherichia coli and Salmonella sp. It was also possible to detect that the largest concentrations of metal ions in the sludge favored the occurrence of bacterial resistance to antibiotics. The occurrence of pathogens, heavy metals and other emerging pollutants in sewage indicates that the sludge requires proper treatment, to provide safe agricultural reuse or disposal.

The techniques applied for monitoring sludge were effective to check the risk of resistant microorganisms input into the environment. Studies concerning sewage treatment plants’ final effluents can bring additional data about the incorporation of such microorganisms into aquatic environments.

The results made possible to observe the need to provide post-treatment for the sludge, especially of the sludge obtained from the anaerobic fluidized bed reactor, since the removal of pathogens, as well as the nutrients, is not satisfactory.