Estimation of COD removal via soft sensor

In conventional wastewater treatment one of the main problems confronting the plant manager is the estimation of the organic carbon removal efficiency, from which a mass balance can be computed. This paper presents a simple, albeit approximate, solution to this problem via a soft sensor approach. The basic idea is to apply a set-point control to the dissolved oxygen in the aerated compartment, so that the air supply is directly proportional to the removed rapidly degradable COD and to use the air supply information as an indirect estimation of the metabolized fraction of the biodegradable carbonaceous load. The paper analyses the performance of the soft sensor in a variety of operational situations.