Biochemical oxygen demand measurement by mediator method in flow system

•A flow system of the mediator method for BOD measurement (BODMed-FS) was reported at the first time.•The BODMed-FS overcame the problems of previous BODMed method using suspended microorganism.•It can measure BOD values within 30 min and possesses a long-term stability up to 2 months.•A linear range from 2 up to 200 mg L−1 was obtained for measuring GGA without the need of dilution.

Using mediator as electron acceptor for biochemical oxygen demand (BOD) measurement was developed in the last decade (BODMed). However, until now, no BODMed in a flow system has been reported. This work for the first time describes a flow system of BODMed method (BODMed-FS) by using potassium ferricyanide as mediator and carbon fiber felt as substrate material for microbial immobilization. The system can determine the BOD value within 30 min and possesses a wider analytical linear range for measuring glucose–glutamic acid (GGA) standard solution from 2 up to 200 mg L−1 without the need of dilution. The analytical performance of the BODMed-FS is comparable or better than that of the previously reported BODMed method, especially its superior long-term stability up to 2 months under continuous operation. Moreover, the BODMed-FS has same determination accuracy with the conventional BOD5 method by measuring real samples from a local wastewater treatment plant (WWTP).

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