Multimedia fates and ecological risk control strategies of phthalic acid esters in a lake recharged by reclaimed water using the QWASI fugacity model

• We used QWASI to simulate the fate of PAEs in a lake recharged by reclaimed water. • The model identified DBP and DEHP as the focal risk objects in the lake ecosystem. • DBP mostly distributed in water, while most of DEHP distributed in sediment. • DBP and DEHP in the lake mainly came from reclaimed water and air, respectively. • We propose quantitative risk control strategies for PAEs in the lake system. Reclaimed water used for lake recharge can bring a variety of pollutants, such as phthalic acid esters (PAEs), into the lake and thus pose a potential threat to aquatic ecosystems. In this study, the fates of the 4 PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP)) in a lake recharged by reclaimed water were simulated using the QWASI model. Results showed that atmospheric input was the main source of DMP (72.97%) and DEHP (87.64%), and reclaimed water replenishment was the main source of DEP (81.02%) and DBP (82.53%) in the lake. In the lake system, most of DMP (85.45%), DEP (68.40%) and DBP (51.58%) distributed in water, while most of DEHP (75.43%) were in sediment. The hazard quotient (HQ) calculating results showed that DBP in sediment (0.27) posed a low ecological risk, and DEHP in water (4.84) and sediment (1.03) posed medium ecological risks. Then the risk control strategies of DBP and DEHP were proposed through multi-scenario simulation of 4 schemes and mathematical fitting between controllable source factors and hazard quotients. The risk of DBP in the lake could be effectively reduced by decreasing its level in reclaimed water. For the reduction of DEHP risk, it is necessary to combine the optimization of reclaimed water recharge with air source control. This study also provides a method for quantitative management of comprehensive ecological risk of multiple contaminants in reclaimed water for lake recharge.