RESUMO
Although many studies have addressed the ability of subsurface filtration systems to remove emerging contaminants from wastewater at micro- and mesocosm-scale, little is known about their performance on full-scale wastewater treatment facilities. To understand better how effective these systems can be for municipal wastewater polishing, we assessed the ability of a full-scale lagoon-subsurface filter system located in Dunnottar, Manitoba, Canada, to attenuate regulatory wastewater parameters, nutrients, pharmaceuticals, and toxicity over the course of the discharge periods in 2015 and 2016 (June-October). Pharmaceuticals included ß-blockers, anticonvulsant drugs, and macrolide and sulfonamide antibiotics. Out of six consistently detected pharmaceuticals, four were efficiently removed through lagoon treatment (e.g. clarithromycin, metoprolol, propranolol), while two persisted to a certain extent (e.g. carbamazepine, sulfamethoxazole), even after subsurface filtration. Attenuation was observed for nutrients with averages of 40% and 60% for ammonia and total phosphorus respectively within the filter, consistent with previous pilot-scale studies at this facility. Compliance with regulations for conventional wastewater parameters at the effluent was observed, as well as reduced acute toxicity (as determined by Microtox®) from the primary lagoon to the effluent, and little likelihood of acute toxicity in receiving waters. Our results suggest that first, the full-scale system has an overall similar performance when compared to the previously studied pilot-scale system; second, there was no apparent effect of acclimation on the attenuation of studied contaminants or toxicity; and finally, the concentrations of contaminants do not appear to pose an acute risk for aquatic species in the receiving environment.
Assuntos
Esgotos/química , Poluentes Químicos da Água/química , Medição de Risco , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análiseRESUMO
The treatment of municipal wastewater in the Arctic is challenging due to a variety of financial, operational, climatic and technical issues. To better understand the efficacy of current wastewater treatment in this region and the hazard posed to receiving waters, we assessed the occurrence of nutrients and contaminants (i.e., pharmaceuticals, antibiotic resistance genes) as they moved through a lagoon-based treatment system in Cambridge Bay, Nunavut, Canada. Wastewater treatment in this community is performed by the use of a lagoon-tundra wetland system that is discharged into the marine environment and is representative of current common practices throughout the region. In 2014, samples were collected before and during lagoon discharge from two locations in the main lagoon, one location downstream from the lagoon effluent and three locations offshore. Grab samples were collected to measure nutrients (e.g., total nitrogen and phosphorus) and the presence of antibiotic resistance gene-bearing microbes, and Polar Organic Chemical Integrative Samplers (POCIS) were deployed to collect passively organic contaminants in all locations. A total of six pharmaceuticals were detected from a screen of twenty-eight analytes during the study: atenolol, carbamazepine, clarithromycin, metoprolol, sulfamethoxazole and trimethoprim. The greatest concentrations of nutrients, antibiotic resistance genes (ARGs), and pharmaceuticals were found in sampling locations within the treatment lagoon. Offshore of the release point, we observed limited to no detection of pharmaceuticals and ARGs, but no change in total nitrogen and phosphorus from pre-release. We conclude that the current concentrations of monitored pharmaceuticals do not pose a significant hazard at this time to aquatic organisms in Cambridge Bay.