Formaldehyde concentration in discharge from land based aquaculture facilities in Atlantic Canada.

Formaldehyde is used in freshwater aquaculture facilities in the Maritimes region of Canada to prevent external parasites and is discharged without treatment to freshwater receiving environments. In this study, formaldehyde was measured at effluent outfalls and 100 m downstream of four land based aquaculture facilities at various post-treatment time intervals. Concentrations of formaldehyde ranged from 0.2 to 7.1 mg/L. Based on Environment Canada's environmental no effect value, all of the samples show a potential risk to aquatic life. Furthermore, based on a chronic aquatic life water quality criterion of 1.61 mg/L all but two of the samples had concentrations considered to be toxic to aquatic life. An acute water quality criteria was only exceeded once in all of the environmental measurements of formaldehyde. These results lead us to hypothesize that the discharge of formaldehyde from land-based facilities may cause adverse chronic impacts.