Water Pipe Replacement Scheduling Based on Life Cycle Cost Assessment and Optimization Algorithm

Fatemeh Ghobadi,Gimoon Jeong,Doosun Kang

doi:10.3390/w13050605

Abstract

Water distribution networks (WDNs) comprise a complex network of pipes and are crucial for providing potable water to urban communities. Therefore, WDNs must be carefully managed to avoid problems such as water contamination and service failures; however, this requires a large budget. Because WDN components have different statuses depending on their installation year, location, transmission pressure, and flow rate, it is difficult to plan the rehabilitation schedule within budgetary constraints. This study, therefore, proposes a new pipe replacement scheduling approach to smooth the investment time series based on a life cycle cost (LCC) assessment for a large-scale WDN. The proposed scheduling plan simultaneously considers both the annual budget limitation and the optimum expenditure on the useful life of pipes. A multi-objective optimization problem consisting of three decision-making objectives—minimum imposed LCC on the network, minimum standard deviation of annual investment, and minimum average age of the network—is thus solved using a nondominated sorting genetic algorithm to obtain an optimal plan. Three scenarios with different pipe replacement time spans and different annual budget constraints are considered accordingly. The results indicate that the proposed scheduling framework provides an efficient water pipe replacement scheduling plan with a smooth management budget.

Highlights

A water distribution network (WDN) comprises a complex network of underground pipes and plays a key role in delivering potable water to urban communities [1]
Three scenarios with different replacement time boundaries and budget limitations were defined by targeting the minimum imposed life cycle cost (LCC), minimum standard deviation (SD) of the annual investment, and minimum average age of the WDN
For individual pipes in a real-life WDN, the results of the simulation proposed the replacement times, and four scheduling plans were evaluated based on four different budgetary viewpoints and decision-maker opinions

Summary

Introduction

A water distribution network (WDN) comprises a complex network of underground pipes and plays a key role in delivering potable water to urban communities [1]. Water infrastructure managers worldwide are facing the problem of aging pipes in WDNs, and limited historical data have hampered cost-efficient replacements. Pipelines age because of various internal and external factors that lead to a decrease in their functionality and an increase in their risk of failure; both of these issues can incur large social and economic costs [4]. Suitable pipe replacement/rehabilitation requires a large budget. For a considerable proportion of WDN assets, an efficient and practical pipe replacement scheduling plan must satisfy the annual budget and minimize future costs while maintaining WDN functionality. Over the last two decades, various methods have been developed to assist in WDN infrastructure management by determining the optimal replacement age based on deterioration failure, leakage, and breakage modeling coupled with additional parameters such as hydraulic capacity [6]

Methods

Results

Conclusion