PW01 Assessment
Exhibit Hall
8:00 AM - Wednesday
(PW008) Release of zinc to municipal wastewater treatment plants (WWTP) from stripping of zinc-containing floor finishes.
Long, K1, Baird, S2, Daggett, D1, Hamilton, J1, 1 JohnsonDiversey Inc, Sturtevant, WI, USA2 Environmental Consultant, UK
ABSTRACT- Cationic zinc is used by manufacturers to cross-link acrylic polymers formulated into acrylic floor finishes. Zinc is present in wastewater solutions from floor finishes that are solubilized (i.e., stripped) from floors during routine building maintenance operations. However, whether zinc from floor finishes can be associated with unreasonable risk to wastewater and the aquatic environment is poorly understood. Therefore, the purpose of this environmental risk assessment was to characterize the environmental impact of zinc used in floor finishes following its disposal into wastewater from floor stripping solutions to conventional urban wastewater treatment plants (WWTPs). Two types of scenarios were considered: a) Scenario 1 is based on zinc releases expected from floor stripping procedures in a US retail store; b) Scenario 2 is based on estimates of the annual release of zinc from the full market of acrylic floor finishes sold in the US. The PEC:PNEC ratio for zinc was determined for four environmental compartments: activated sludge, receiving rivers, coastal zones, and sludge-amended soil. Results of this risk assessment demonstrate that the PEC:PNEC ratio was well below one for all the floor finish scenarios examined, indicating that for floor stripping procedures, there is not an unreasonable risk for adverse effects from zinc discharged to WWTPs. Regulatory authorities have restricted the discharge of zinc to manage the impact of zinc on wastewater treatment processes and aquatic environments. Further, eco-labeling programs such as Green Seal and Environmental Choice have proposed use of alternative cross-linking agents to replace zinc in floor finishes. However, for floor stripping procedures, this assessment indicates that there is not an unreasonable risk for adverse effects from zinc discharged to WWTPs. Therefore, recommendations to replace zinc in floor finishes are not supported by this risk assessment.
Key words: risk assessment, zinc, eco-labelling