This document specifies the general principles and provides guidance on the quantitative characterization of the life cycle cost of a complete wastewater management system, including collection, treatment and, optionally, reuse. It enables the consideration of different degrees of distribution, including non-sewered systems for one or more dwellings and associated trucking operations.

The methodology provided in this document is applicable to urban or rural areas wherein several decentralized wastewater treatment and reuse systems can provide a lower cost solution than a single centralized plant. Similarly, the same methodology can be applied for industrial reuse systems, where several separate plants on a large industrial site can be considered instead of one treatment system.

The scope of this document includes the following:

a)       Guidance on the determination of the degrees of distribution of decentralized wastewater treatment and reuse systems.

b)       A definition of the elements and components included in the life cycle cost of the different degrees of distribution in wastewater management systems, including construction, operation and maintenance.

c)        Guidance on the required steps for calculating life cycle cost indicators, including considerations of term and interest, operation and maintenance, replacement parts, equipment life expectancy, the value of water for reuse and other income from by-products.

d)       A definition of the metrics for reporting results, including the cost per unit, scope, term and interest.

The following secondary costs and other considerations are not within the scope of this document:

—     cost of eventual disposal of the system;

—     guidance on wastewater treatment process selection and design;

—     health and sustainability considerations (although health and sustainability are primary considerations in design and decisions);

—     social impact factors and/or environmental risks and impacts.