Estimation of raw sewage discharge resulting from sewer network failures

The raw sewage volume potentially discharged from a sewer network to the environment arising from its component failures is proposed as a measure of overall system reliability. This paper presents a simple method for quickly and properly calculating this volume. The basis for this method is a representation of the sewer network by a combination of Y-like fragments named here as structure-forming elements. Each such element is formally substituted by a fictitious equivalent sewer with a failure rate leading to the same output for the same input. A sequential application of this approach reduces the problem of estimating the discharged sewage volume to elementary subproblems for which the solution is simple. Examples are used to demonstrate the possibilities of this method.