Spectrophotometric Determination of Biochemical Oxygen Demand in Water Sample by I3–- Acridine Red-Polyvinyl Alcohol System

Abstract

The use of the conventional 5-day biochemical oxygen demand (BOD5) method in BOD determination is greatly hampered by its time-consuming sampling procedure and it is insensitive to the variation of dissolved oxygen less than 0.1 mg/L in water sample. Meanwhile the BOD5's titration has technical difficulty in the handling of a large pool of wastewater samples within short time. This paper describes a high-throughput and sensitive method for the determination of BOD in wastewater depending on measurement of the dissolved oxygen. Based on the reaction between I₃^– and acridine red to give an ion-association complex with a characteristic absorption at 525 nm, a photometric method for determination of oxygen demand in water was proposed. Then BOD5 could be calculated through the amount of dissolved oxygen before and after the seeding procedure determined by the proposed spectrophotometry. This biochemical oxygen demand method was found to be able to determine the BOD values of 20 waste samples within 40 min by monitoring the dissolved oxygen concentrations. Moreover, the BOD values determined by the proposed method were in good agreement with those obtained by the GB7488- 87 (BOD5) method.