A methodology for identifying best areas for sewerage system expansion.

摘要

Immediate collection and treatment of wastewater generated from residences, commercial and other facilities reduces environmental, public health, and other socio-economic problems. Onsite treatment systems are commonly used in rural and impoverished areas where centralized wastewater treatment facilities are unavailable. However, onsite systems often fail, resulting in untreated wastewater discharges. Thus, centralized sewage collection and treatment systems are important components of a healthy population and economy.; In reality, sufficient financial resources are not available to immediately expand sewerage system services into all unserviced areas. Thus, decision makers must develop a means for objectively selecting areas that should be prioritized to receive sewerage system. This research develops an approach utilizing dynamic programming (DP) algorithms to select best areas in which to expand sewerage system. This methodology considers costs and benefits of each alternative while taking into account limitations of available resources. Resources are monetary funding for sewerage expansion and hydraulic capacities for wastewater collection and treatment.; For proper identification of sewerage project, this approach develops three models: (i) collection system DP model to identify potential areas to expand sewage collection system, (ii) transportation system DP model to select optimum routes of wastewater transportation and (iii) benefit estimation model. In contrast to conventional benefit analysis, benefit estimation in this approach makes no attempt to convert all the consequences of a sewerage project into a monetary measure. Rather, benefit is quantified as a dimensionless number based on the change of adverse environmental, public health and other economic or noneconomic consequences as a result of sewerage provisions.; The methodology developed in this research can identify best areas as a function of funding or for a given funding constraint. The models have the ability to generate a matrix of optimal and suboptimal sewerage plans while allowing the decision makers to satisfy their underlying goals and assumptions. This methodology can be a powerful decision tool when the necessary data are available. The methodology is applied to wastewater system in Ensenada, Mexico to identify best areas for sewerage expansion. Currently, Ensenada has 16 unsewered areas and 3 treatment plants with adequate information to be used in these models.