There is increasing pressure to reduce copper concentration in sewage effluents from treatemnt works discharged to natural waters. Regulator consents are based on Environmental Quality Standards (EQS) related to the toxicity, biology and chemistry of a substance in the aquatic environment.
Complexion of copper with natural organic ligands results in a greatly reduced toxicity. This reduction in copper toxicity is taken into account with the EQS, where a caveat states, "The EQS may be exceeded where there is demonstrable copper complexation by organic ligands".
The research supported by 3 Water Utilities investigated the degree of copper complexation in final effluents and receiving waters, and how it potentially affected the toxicity of copper to aquatic organisms.
- Enabled the Water Utilities to identify how much copper present in their works final effluent was strongly bound to organic ligands thus reducing its toxicity considerably
- Investigating the receiving waters revealed how much copper was present in the relatively less toxic organically-bound form.
- These results enabled good discussions with the Regulators based upon the scientific analysis and meeting the EQS's for copper in the aquatic environment.