Quantifying biodegradable organic matter in polluted water on the basis of coulombic yield

Biodegradable organic matter (BOM) in polluted water plays a key role in various biological purification technologies. The five-day biochemical oxygen demand (BOD₅) index is often used to determine the amount of BOM. However, standard BOD₅ assays, centering on dissolved oxygen detection, have long testing times and often show severe deviation (error ≥ 15%). In the present study, the coulombic yield (Q) of a bio-electrochemical degradation process was determined, and a new index for BOM quantification was proposed. The Q value represents the quantity of transferred electrons from BOM to oxygen, and the corresponding index was defined as BOM_Q. By revealing Q-BOM stoichiometric relationship, we were able to perform a BOM_Q assay in a microbial fuel cell involved technical platform. Experimental results verified that 5-500mgL^-1 of BOM_Q toward artificial wastewater samples could be directly obtained without calibration in several to dozens of hours, leaving less than 5% error. Moreover, the BOM_Q assay remained accurate and precise in a wide range of optimized operational conditions. A ratio of approximately 1.0 between the values of BOM_Q and BOD₅ toward artificial and real wastewater samples was observed. The rapidity, accuracy, and precision of the measurement results are supported by a solid theoretical foundation. Thus, BOM_Q is a promising water quality index for quantifying BOM in polluted water.