Wastewater inflow and infiltration reduction - Where does NZ sit on the world scene?

The New Zealand Infiltration and Inflow Control Manual10 was published by Water New Zealand (then known as the New Zealand Water and Wastes Association) back in 1996. Over the past 15 years, there has been a significant amount of work done throughout New Zealand in I/I management. Little else has evolved over this time in terms of the documentation of the learnings from this work and guidelines that incorporate these learnings.

The Water Services Association of Australasia (WSAA) is an industry membership organization that represents the 25 largest water companies/authorities in Australia. They recently undertook an I/I Benchmarking and Best Practice Guideline Document project aimed at determining the range of current I/I management practices in use across Australia. These practices and the resulting I/I reduction outcomes were compared and benchmarked with practices in New Zealand, Canada, USA and South East Asia.

Using the identified examples of successful project outcomes, a Best Practice I/I Management Guideline Document for Australian water utilities was developed. This document is set to become the guideline document for I/I management programmes across Australia.

This paper outlines the result of this exercise and in doing so gives a clear picture of where I/I management practices and outcomes being achieved here in New Zealand are at in relation to those in the researched countries. It also discusses the Best Practice Guideline Document and its applicability for use New Zealand water industry going forward.

This paper will be of interest to the wide range of delegates challenged by the issue of infiltration and inflow in the effective management of their wastewater systems.