Banner 4

An inline sensor for recycled water cross-connections


Impact theme: More about impact themes
Technology and Treatment


Recycled water is now commonly supplied to properties using a dual reticulation system with two sets of pipes—one for drinking water, and one for recycled water used for flushing toilets and outdoor uses. Cross-connections, misconnections and water system faults occasionally cause the two supplies to mix, impacting drinking water quality. Early-warning technology to support smart water metering at individual premises would improve safety and increase public confidence in these third-pipe schemes. This project aims to develop an automated sensor that measures water quality in pipes (or ‘inline’) in real-time by testing both ultraviolet (UV) absorbance and fluorescence and immediately warn of such mixing.

The project aims to be able to reliably detect as little as 10 per cent contamination of potable water with recycled water. A paired sensor will be developed in the form of an inline sensor that measures electrical conductivity to enhance the detection of contamination of potable water with recycled water, using existing CSIRO technology.


Work undertaken and outcomes to date

Four sensors have been constructed, verified that their outputs are consistent, and are now ready for field trial. Each of these sensors has been demonstrated to detect down to 1 per cent recycled water in potable water in the laboratory environment. Temperature has been found to influence the sensitivity of detection significantly, and its effect needs to be measured with precision to reliably detect real cross-connections.

A field prototype system, pairing an electrical conductivity sensor from Hawk Measurement Systems with a fluorescence sensor is being trialled in the laboratory on a range of water qualities to test its robustness and to debug any control issues. Field testing will be conducted in the near future at two recycled water facilities.


Adoption and impact

Field trials at two water treatment facilities will evaluate and demonstrate stable long-term performance of the sensing system for commercialising and marketing to Australian utilities and domestic water supply operators.


Michael Best, CSIRO, undertaking water quality measurements with four inline flourescence sensor prototypes



Field unit to test the ability to detect cross-connections being assembled


Project Partners

Lead organisation: Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water Flagship
Partner organisations: Smart Water Fund
Melbourne Water
Yarra Valley Water
Western Water
Hawk Measurement Systems


Return to project listing