Compensation and Simulation of Restrictive Memory Least Square Method for BOD Soft Measurement Mechanism Model

In order to overcome the difficulty of on-line measurement for output water quality such as BOD (biochemical oxygen demand) in the waste water process, a second-order soft measurement model based on Lawrence-McCarty formula is established. And to improve the precision of model formula, the restrictive memory least square method is used to identify the system parameter and then the identified model is utilized to compensate the measurement error of the Lawrence-McCarty formula. The established model and its compensating accuracy are tested by laboratory measurements, and the results show that the compensated mixed model is superior to the original soft measurement formula. This combined model can be used in different water qualities and provide parameters on-line measurement for waste water process.