Oxidation-reduction potential as a monitoring tool in a low dissolved oxygen wastewater treatment process

Research was undertaken to investigate the relationship between two biochemical events and the oxidation-reduction potential (ORP) measurement in a low dissolved oxygen (D.O.) wastewater treatment process. The biological events considered were the depletion of organic waste and the depletion of ammonia nitrogen. Two lab-scale sequencing batch reactors fed with a synthetic waste were operated under controlled conditions using seed material from a local wastewater treatment plant. The on-line monitoring, of ORP, D.O., and pH was complemented by intensive track studies in which physical measurements of biochemical parameters such as chemical oxygen demand and TN were taken. The results indicated that low D.O. processes (e.g., the simultaneous nitrification/denitrification process) may have their own distinctive on-line profiles, with certain biochemical events such as the depletion of organic carbon and the depletion of ammonia nitrogen being readily detectable on the ORP profile. The fact that these specific events are displayed on the on-line ORP profile means that the profile could possibly be used as a process control parameter.