A co-immobilized mediator and microorganism mediated method combined pretreatment by TiO2 nanotubes used for BOD measurement

► Co-immobilized microbes and mediator were used in BODMed method. ► Modifying GCE (gPVP/E. coli/NR)p/GCE and (gPVP/E. coli)/PNR/GCE were compared. ► TNTs pretreatments were utilized for enhancing electrochemical signal. ► Different effects of TNTs pretreatments for OECD, GGA, urea and real wastewater.