Cost comparison of centralized and decentralized wastewater management systems using optimization model

Area of Science:

• Environmental Engineering
• Water Resource Management
• Sustainable Infrastructure

Background:

• Growing interest in decentralized wastewater management (DWWM) as an alternative to centralized wastewater management (CWWM) in developing countries.
• Limited understanding of the comparative costs between CWWM and DWWM systems.
• Need for cost-effective and sustainable wastewater solutions in rapidly developing regions.

Purpose of the Study:

• To simulate and compare the costs of cluster-type DWWM with conventional centralized wastewater management (CWWM).
• To analyze the impact of the number and layout of cluster subsystems on DWWM costs.
• To evaluate DWWM as a viable, cost-competitive alternative to CWWM in specific contexts like Alibag, India.

Main Methods:

• Development of a three-step model to simulate various DWWM configurations.
• Simulation of cluster-type DWWM using simplified sewers and Decentralized Wastewater Treatment Systems (DEWATS).
• Comparison with a conventional CWWM system featuring standard sewers and an activated sludge plant.

Main Results:

• DWWM costs increase nonlinearly with the number of cluster subsystems due to reduced economies of scale for DEWATS.
• Layout variations resulted in ±5% cost fluctuations for DWWM configurations with the same number of clusters.
• DWWM was found to be less expensive than CWWM for configurations with fewer than 16 clusters in Alibag.
• DWWM exhibited lower operation and maintenance requirements but higher capital and land needs compared to CWWM.

Conclusions:

• Cluster-type DWWM, utilizing simplified sewers and DEWATS, presents a cost-competitive alternative to CWWM.
• Strategic configuration of DWWM, particularly the number and layout of clusters, is crucial for cost-effectiveness.
• DWWM offers potential benefits in reduced operational costs, though initial capital and land investments need consideration.