Side-chain fluorinated polymer surfactants in biosolids from wastewater treatment plants

High concentrations of the main components in Scotchgard™ fabric protector products (pre-2002 and post-2002; side-chain fluorinated polymer surfactants, S1 and S2, respectively) were detected in biosolids samples from twenty pan-Canadian wastewater treatment plants (WWTPs). Based on mass spectrometric analysis, S1 and S2 can be named as side-chain perfluorooctane sulfonamide-urethane polymer and side-chain perfluorobutane sulfonamide-urethane polymer, respectively. S1 (with C₈F₁₇ side-chain) concentrations ranged from 1.08-105 ng/g d.w. and S2 (with C₄F₉ side-chain) concentrations ranged from 37.5-2051 ng/g d.w., which were much higher than that of other commonly monitored perfluoroalkyl substances (PFAS). S1 and S2 concentrations were significantly correlated (p < 0.001; r² = 0.6142) indicating similar source origins. A negative linear correlation was observed (p < 0.05) between concentrations of S1 (or S2) with the volume of WWTP treated wastewater per day per person (m³/person/day). The total concentration of 22 other PFAS ranged from 4.93 to 92.6 ng/g d.w., and approximately thirty times lower than S1 and S2 concentrations. The calculated elemental fluorine concentrations of ƩF_S1&S2 were generally much higher than the sum of the other PFAS. PFAS concentrations in biosolids are likely underestimated without consideration of S1 and S2.