Seasonal occurrence, removal and mass loads of artificial sweeteners in the largest water reclamation plant in China.

Artificial sweeteners (ASs) are of growing concern as an emerging contaminant. In the study, the seasonal occurrence, removal and mass load of six ASs in sewage, suspended particulate matter (SPM) and sludge were investigated throughout the treatment process of the largest water reclamation plant in China. The highest ASs concentrations in the influent (13.0 μg/L), effluent (2.22 μg/L), SPM (4.48 μg/g) and sludge (0.15 μg/g) were observed in the dry season, which were 1.24- to 5.0-fold higher than in the normal season and 1.06- to 37.5-fold higher than the flood season. Following treatment, ASs concentrations decreased by 24.3 %, 51.7 % and 5.1 % (on average) in primary, secondary and reclaimed processes, respectively. Among the investigated ASs, acesulfame (93.1 %) and cyclamate (98.4 %) were removed most efficiently, with removal occurring mainly in secondary processes, while sucralose exhibited the lowest removal efficiency (38.7 %). Seasonal characteristics affect the consumption of ASs, which subsequently changes the input and discharge ASs loads of STPs. The maximum mass load of ASs occurred in the dry season, ranging from 0.002 (neotame) to 1.33 mg/d/person (cyclamate), while the maximum emission load occurred in the flood season, ranging from 0.003 (neotame) to 0.83 mg/d/person (sucralose). The mass and emission load of ASs in Beijing is significantly lower than in European or the United States, due to Beijing having low per capita consumption of ASs (5.50 mg/d/person). The highest ASs risk in the receiving water occurred in the flood season due to the input of other pollution sources by rainfall runoff. Meanwhile, attention should be paid to the risk of receiving water close to the STP outlet in the dry seasons for the highest ASs concentration in the STP effluent in the season. The present study provides important guidance on controlling the input and reducing the emission of ASs in different seasons.