Case-Based Reasoning (CBR) is one of the emerging paradigms for design
ing intelligent systems. Preliminary studies indicate that the area is
ripe for theoretical advances and innovative applications. Heuristic
search is one of the most widely used techniques for obtaining optimal
solutions to many real-world problems. We formulated the design of wa
stewater treatment systems as a heuristic search problem. In this arti
cle we identify some necessary properties of the heuristic search prob
lems to be solved in the CBR paradigm. We designed a CBR system based
on these observations and performed several experiments with the waste
water treatment problem. We compare the performance of the CBR system
with the A search algorithm.