Field application of a biofilm reactor based BOD prototype in Taihu Lake, China

► A biofilm reactor based protype was used for determination of BOD. ► The protype needs only tap water to operate and requires no chemical reagent. ► The organic compounds in municipal tap water brought a negative deviation. ► Inorganic ions in low concentrations influenced the microbial endogenous respiration. ► The automated monitoring showed that BOD of Taihu Lake maintained at a low level.