Biochemical oxygen demand (BOD) is a significant indicator to evaluate the effluent quality in wastewater treatment process. Complex wastewater treatment process and high requirement for instrument maintenance make it very difficult to obtain BOD quickly and accurately. In order to solve this problem

a novel BOD on-line soft measuring model based on fast variable relevance vector machine (Fast-RVM) is proposed in this paper. Relevance vector machine algorithm with Bayesian framework is used to build up predictive model and fast marginal likelihood algorithm is applied to accelerate updating speed of the model. Simulation experiments show that the real-time on-line prediction performance and generalization ability are better by using the proposed model than those of off-line model. The online updating speed is particularly outstanding. These experimental results verify that the proposed method is very suitable for real-time on-line prediction of effluent quality in the wastewater treatment process.