Description
When modeling an activated sludge system of a wastewater treatment
plant (WWTP), several conflicting objectives may arise. The proposed formulation
is a highly constrained bi-objective problem where the minimization of the
investment and operation costs and the maximization of the quality of the effluent
are simultaneously optimized. These two conflicting objectives give rise to a set of
Pareto optimal solutions, reflecting different compromises between the objectives.
Population based algorithms are particularly suitable to tackle multi-objective problems
since they can, in principle, find multiple widely different approximations to
the Pareto-optimal solutions in a single run. In this work, the formulated problem
is solved through an elitist multi-objective genetic algorithm coupled with a constrained
tournament technique. Several trade-offs between objectives are obtained
through the optimization process. The direct visualization of the trade-offs through
a Pareto curve assists the decision maker in the selection of crucial design and operation
variables. The experimental results are promising, with physical meaning and
highlight the advantages of using a multi-objective approach.