QUAT-fate has demonstrated that Quaternary Alkylammonium compounds (QUATs) have been and are being sold and used heavily in Denmark to “clean” roofs and terrasses. The compounds used in these products are identical to those used in biocidal applications but different to those used in fabric softeners. QUAT-fate determined that the transformation of QUATs is relevant. The respective transformation products have been characterized in the project: QUATs can be photo-oxidized which is relevant as they will be exposed to sunlight when used on rooftops and terrasses. QUATs can be metabolized by microorganisms in wastewater treatment plants, which emit these metabolites. QUATs are found at high concentrations (> 5 µg/L, i.e., exceeding the PNEC) in the discharge water from stormwater drainage systems and thus introduced into the recipients and stormwater ponds, which agrees to rumors around Denmark on fish kills due to runoff collected from roofs being directed to waters with fish populations.
QUATs were found at high concentrations (µg/L) in untreated wastewater. QUAT-Fate was able to demonstrate that removal of QUATs in wastewater treatment plants is high due to both sorption and biodegradation, thus concentration (<0.001-0.04 µg/L) in effluent wastewater that is discharged into the aquatic environment are low.
In contradiction to that, the concentrations in selected recipient samples were high (0.1 µg/L). An extensive study in the recipients showed, that dry weather concentrations are low (<0.001 µg/L) while concentrations during wet weather are high (>0.1 µg/L. This behavior is consistent with the main introduction of QUATs occurring with discharged stormwater from the urban areas, while the wastewater treatment plants are a minor source.