Author(s):
Novo, Ana 
; Manaia, Célia M.
Date: 2010
Persistent ID: http://hdl.handle.net/10400.14/4891
Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
Subject(s): Wastewater treatment; Antibiotic resistance; Amoxicillin; Tetracycline; Ciprofloxacin
Description
Municipal wastewater treatment plants are
recognized reservoirs of antibiotic-resistant bacteria.
Three municipal wastewater treatment plants differing on the
dimensions and bio-treatment processes were compared for
the loads of amoxicillin-, tetracycline-, and ciprofloxacinresistant
heterotrophic bacteria, enterobacteria, and enterococci
in the raw inflow and in the treated effluents. The sewage
received by each plant, in average, corresponded to 85,000
inhabitant equivalents (IE), including pretreated industrial
effluents (≤30%) in plant activated sludge, 105,000 IE,
including pretreated hospital effluents (≤15%) in plant
trickling filter, and 2,000 IE, exclusively of domestic sewage,
in plant submerged aerated filter. The presence of pretreated
industrial effluents or of pretreated hospital sewage in the raw
inflow did not imply significantly higher densities (per
milliliter or per IE) of antibiotic-resistant bacteria in the raw
wastewater. Longer hydraulic residence periods (24 h)
corresponded to higher bacterial removal rates than shorter
periods (12 and 9 h), although such efficiency did not imply
significant average decreases in the antibiotic resistance
prevalence of the treated effluent. The bacterial loads in the
treated effluent could be ranked according to the treatment
efficiency, suggesting that the characteristics of the raw inflow
may have less relevance on the quality of the treated
wastewater than other aspects, such as the inflow volume, the
type of biological treatment, or the hydraulic residence time.
