Remote water treatment challenges

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Challenge

The Tjuntjuntjarra remote inland Indigenous community is located 800km northeast of Kalgoorlie, Western Australia, with a population of 120 people. The growing community requires more freshwater than can be supplied by the current source: a shallow lens which overlies saline groundwater. The existing freshwater lens resource contains an average concentration of 90 mg L‐1 of nitrate, which is above the Australian Drinking Water Guidelines (2004) for infants and approaching the adult limit of 100 mg/L‐1. The saline groundwater concentration is approximately 120‐150% that of seawater, which is generally considered to be too energy intensive for the use of reverse osmosis (RO) technologies. The exploration for alternative freshwater supplies in the area has not been successful, which is the catalyst for this unique collaborative project.

The challenge is to develop a suitable and sustainable desalination system to provide drinking water with a strong focus on reliability. The freshwater lens is recharged through surface runoff, which is highly susceptible to rainfall variability and surface contamination.

Investigation

Evaluation of a prototype 1kl/day vacuum multi-effect membrane desalination unit to provide desalinated water. The majority of the energy needed to operate the unit is in the form of heat energy (and so potentially amenable to solar thermal or diesel waste heat recovery systems), with a much smaller amount of energy required for the vacuum and pumps, overall much less than the amount required for conventional RO desalination units. The prototype unit would be tested at the Rockingham Desalination Research Facility before being modified and tested in Tjuntjuntjarra. The combination of an electric heater and solar thermal system will be tested to provide the thermal energy input required by the unit. A smaller version of the unit will tested in the laboratories at UTS and used to assist in the development of a pre-treatment process.

Outcomes

The initial assumption was that the prototype unit would be ready for deployment in the field, after some modifications to make it for robust for outback Australian conditions, and linking it to the solar thermal system. Early on it became apparent the unit, although capable of producing some very promising results, needed considerable modifications before it could be deployed.  The control system was revamped to allow the unit to safely shutdown under a range of error conditions and a flushing protocol was developed to maintain the integrity of the membranes. Water quality assessment of the site water under various scenarios revealed potential problems that would arise – given the quality and composition of the water and the temperatures and vacuum conditions that the water would experience inside the unit.

The result was that the water would require a more intensive pre-treatment process before it could be effectively treated by the unit. The unit was installed and tested on site for six months however, despite numerous attempts, the unit was not able to demonstrate continuous site operation and the recommendation was that this technology was not suitable and would ultimately not meet the needs of the community. Extensive water quality analysis of the bore water, a bore pump and pipework are available for a more suitable system to be investigated and trialled.

Future Direction

The vacuum multiple effect membrane distillation system was found to be inappropriate for installation at a remote community, such as Tjuntjuntjarra, without further determination of the requirements to prevent internal scaling in the unit. Other water treatment options need to be investigated for this community and have been discussed with the Department of Housing in the hope that a trial could be initiated using some of the infrastructure provided by this project.

Partners

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Total Value: $1,104,819 (cash and in-kind contributions)

Principal Investigator: Dr Trevor Pryor

Title: Tjuntjunjarra remote inland indigenous community solar/waste energy groundwater desalination project

Length: 34 months

Personnel: 11 collaborators contributed 2.0 FTE

Further Information

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