Seasonal Alternation of an Artificial Sweetener and Dissolved Organic Carbon Concentration in Lake Kojima: From Source to Sink Perspective

Nozomi NAKAHARA*, Shun KUWAMOTO**, Tsugumi SHIOKAWA***, Hiroko Tada**, Morihiro MAEDA**** and Yuko SUGIYAMA**

Water and Environment Technology Conference

Japan Society on Water Environment (JSWE)

City Hall Plaza Aore Nagaoka

https://sites.google.com/jswe.or.jp/wet2025/home?authuser=0

Little is known about the accumulation of artificial sweeteners in sewage treatment plant (STP) effluent and
downstream water environments in Japan. This study investigated the annual influence of non-biodegradable organic
matter in STP effluent on water quality in Lake Kojima. The surface water was sampled at six sites, and the water
quality analysis was performed. Results showed that dissolved organic carbon (DOC) concentration was correlated with
water temperature, whereas chemical oxidation demand (COD) was not. In addition, the biodegradation test suggested
that over 50 % of the COD concentration remained after 100 days. The expected impact of the DOC concentration of
the effluent on the water quality in Lake Kojima was predicted to be between 8.0 and 10 % from summer to winter. No
significant changes in sucralose concentration (average: 2.4 µg/L) were observed throughout the year. However, the
effluent of sucralose conc. (maximum 22 µg/L) was about five times higher than Lake Kojima over the year. Given the
results, we conclude that more than half of the dissolved organic matter in Lake Kojima was considered non-
biodegradable, and the DOC of STP effluent should not be overlooked for the water quality of Lake Kojima.