Potential impact of secondary wastewater treatment plant effluent on the concentration and antibiotic resistance of bacteria in river water

Abstract

Effluent from wastewater treatment facilities can have a major impact on the bacterial populations in water downstream of the outfall point. We sought to assess the impact of wastewater effluent from the Northwest Langley Wastewater Treatment Plant on the concentration of bacteria and the occurrence of antibiotic-resistant bacteria in the Fraser River. We hypothesize that effluent from the plant will increase the amount of antibiotic-resistant bacteria downstream of the plant. In order to assess this, we took five samples of water downstream and five samples of water upstream from the treatment plant’s outfall point and cultured the bacteria in these samples on Mueller Hinton agar, with half of the agar plates containing Ampicillin. We then counted the number of bacterial colonies that grew on each plate. Our results displayed that there were the same amount of bacteria downstream
compared to upstream from the wastewater outfall point. This may be because secondary wastewater treatment is effective enough to remove antibiotics and other toxins from the wastewater effluent. We also observed that antibiotic resistance can be detected in the bacteria before they reach the wastewater effluent. This may be due to exposure to other compounds in the water or from changes in the river flow patterns that allow for the upstream bacteria to come in contact with the effluent. Our results suggest that substances present in wastewater effluent in the Fraser river do not reduce the quantity of bacteria in river water.