Multivariable control of nutrient-removing activated sludge systems

The aim of this paper is to evaluate several multivariable model-based cont rol algorithms for controlling nitrogen removal in activated sludge process es, We contend that the control of nutrient removal in activated sludge sys tems is a multivariable control problem, rather than a multiloop problem. T he work is a simulation study of a predenitrification activated sludge plan t. Several model-based controllers are evaluated and compared against a bas e-case and multiloop controller. We introduce a quantitative measure to aid in controller evaluation. Model based control algorithms are shown to be a ble to provide tight control of N removal, thereby offering significant ben efits in terms of deferred capital expenditure. This is in return for incre ased operating costs. (C) 1999 Elsevier Science Ltd. All rights reserved.