Centralized wastewater treatment, widely practiced in developed areas, involves transporting wastewater from large urban or industrial areas to a large capacity plant using a single network of sewers. Alternatively, the concept of wastewater collection, treatment and reuse at or near its point of generation is called decentralized wastewater treatment. Smaller decentralized plants with energy-efficient reclaimed water pumping, modularization of expansion and minimum capital investment can meet the increasing need for reclamation and wastewater management accessibility in rapidly developing regions Decentralized treatment can improve access to wastewater infrastructure in developing regions and improve energy-efficiency in reclamation in many rapidly growing developed regions. They can also replace land-intensive and inefficient treatment systems such as septic tanks and leach fields for remote, residential communities. They can reduce the strain on existing central facilities and can be an alternative to expensive collection system upgrades. We demonstrated the

applicability of decentralized treatment to two examples in India and an example in Los Angeles.

It is important to study the optimization and implications of decentralization. We formulated design and optimization methodology subject to user-defined constraints for a decentralized configuration of several treatment plants and collection networks. In this dissertation we developed an algorithm, using a constrained multi-objective optimization method (Genetic Algorithm), to obtain feasible decentralized configurations with minimum cost and energy. The applications of this methodology include obtaining the optimal solution for a given scenario, comparing alternative solutions devised by the user, and analyzing capacity expansion. Enabling easier reclamation and a more widespread access to wastewater collection and treatment are the chief motivation behind this study.