Prevention is Better Than Cure - Do Low I/I Sewers Really Work?
Annual Conference
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For more than 20 years, I/I reduction programmes through system rehabilitation works have been a part of wastewater planners’ and managers’ toolbox for reducing wastewater overflows in existing networks . Until the recent publication of The Water Services Association of Australia (WSAA) Good Practice Guideline Document on I/I Management, implementation of this technology has been plagued by uncertainty and risk.
Extending on the discussion of the last chapter of the WSAA Document for designing gravity sewers for low I/I, advances in modern sewer technologies or the replacement of networks with new wastewater systems now means that there is a wealth of information and data about how sewers can be designed to prevent I/I occurring over the life of the asset.
Modern gravity sewers are an evolution of standards and specification which emphasises the use of modern materials (such as PVC or PE). Alternate low infiltration specifications have been developed such as Low Infiltration and Leak Tight (used by Sydney Water) and NuSewer (used by Queensland Urban Utilities).
Building on an established track record overseas, pressure sewer systems are now being installed or being considered in many locations across New Zealand.
Vacuum systems are now also being installed in some locations in New Zealand. Like Low Pressure sewer systems, the technology is intuitively and inherently effective in preventing I/I.
This paper discusses wet weather flow design philosophies that are being adopted in the implementation of these systems both locally and in Australia.
With an operational track record extending to over 10 years now with some of these technologies, the paper also discusses by way of case studies and summaries of the actual I/I performance of these installed and operating systems where such results have been published.
The paper should be of immense value to delegates considering the merits of the installation of alternative wastewater collection system technologies.