Impact assessment of a wastewater treatment plant effluent using the fish biomarker ethoxyresorufin-O-deethylase: field and on-site experiments.

The impact of a wastewater treatment plant (WWTP) effluent was assessed with the fish biomarker ethoxyresorufin-O-deethylase (EROD) using field and on-site laboratory experiments. EROD activity was measured in chub (Leuciscus cephalus) and stone loach (Noemacheilus barbatulus) caught at three sites of the Chalaronne River (southeast France). Liver somatic index (LSI) and organochloride bioaccumulation in muscle were estimated for chub only. In September, EROD activity and LSI of chub increased significantly between the sites above and below the WWTP effluent discharge. EROD induction detected in chub was confirmed by on-site tank experiments. EROD levels were determined in juvenile rainbow trout (Oncorhynchus mykiss) and mirror carp (Cyprinus carpio) exposed to different concentrations of the WWTP effluent and river water for 16 days. After a 4-day exposure, EROD activities of the carp exposed to the effluent increased significantly compared with the control. The response was linked to the effluent concentration and was stable with exposure time. WWTP effluent induced EROD activity, whereas organic and metal analyses, performed on fish muscle and sediment, did not indicate any difference between upstream and downstream of the discharge.