Title:


A dissipative approach to control design for biological wastewater
treatment plants based on entire process models


Speaker:


Hiroshi Ito, Kyushu Institute of Technology
             Associate Professor


Abstract:


Innovation is becoming increasingly necessary for control design of
wastewater treatment(WWT) plants to cope with stricter effluent
legislation.
Processes of WWT consist of biochemical reactions behaving
nonlinearly in a series of reactors interconnected each other.
Naturally, models of WWT plants become very complex and
involve huge numbers of variables, parameters, equations and
nonlinearities.
The development of automatic control exactly based on these
models have been very difficult, and many researchers have been
seeking reduced complexity models and approximations.
Control designs based on local approximate models have not been
satisfactory enough for essential improvement since they may not
utilize the full capacity of WWT plants efficiently.
In this talk, we introduce an approach to control design of biological
WWT plants based on rigorous treatment of the complex mathematical
models from a nonlinear control theoretical viewpoint.
Without resorting to order reduction, localization and linearization
of process models, we provide an avenue to model-based control design
for necessary innovations of modern WWT.
As a fundamental property of WWT systems,
a dissipation property of the entire plant is derived precisely from
the integration of all components of the plant.
For the purpose of efficient removal of carbon and nitrogen,
control laws are proposed so that the dissipation of
the entire plant is preserved in the presence of control inputs.
We demonstrate that utilization of the natural principle,
the dissipation, is very effective in extracting compact global
information of the large-scale complex plant of WWT, and
it enables us
to accomplish a model-based control design taking into account
the whole behavior of the plant.