Elimination of organophosphate ester flame retardants and plasticizers in drinking water purification

Organophosphate ester flame retardants and plasticizers like tris-(2-chloro-, 1-methyl-ethyl)phosphate (TCPP), tris-(2-chloro-, 1-chloromethyl-ethyl)phosphate (TDCP), tris-(2-chloroethyl)phosphate (TCEP), tributylphosphates, triphenylphosphate (TPP), ethylhexyldiphenylphosphate (EHDPP) and tris-(butoxyethyl)phosphate (TBEP) have been studied in diverse processes for drinking water purification. The elimination efficiency of these different treatment processes, e.g., biological active slow underground passage, soil passage and technical treatment processes such as ozonization or multilayer and activated carbon filtration have been studied in three waterworks in the catchment area of the river Ruhr. In the untreated surface water the concentrations of the chlorinated organophosphates ranged 50–150 ng L−1 TCPP, 10–130 ng L−1 TCEP and 10–40 ng L−1 TDCP. The amounts of the non-chlorinated alkylphosphates were in the same order of magnitude (40 ng L−1 of the tributylphosphates, 170 ng L−1 of TBEP and 10 ng L−1 TPP) depending on weather and water flow. EHDPP was detected in the range of 1 ng L−1. After the drinking water purification process in all waterworks in this study, the concentrations of the selected substances were below the respective limit of quantification (0.3–3 ng L−1). While activated carbon filtration as well as extended passage through soil (10–15 days residence time) were effective in eliminating all selected compounds, ozonization and multilayer filtration did not contribute to the elimination of the chlorinated compounds. The elimination effect of slow underground passage combined with soil passage concerning the halogenated compounds seemed to depend on the hydraulic residence time.