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An automated blending device for brackish water desalination: Upscaling the laboratory-scale device for standardised water supply on farms

Tucakovic, Ivana (2020) An automated blending device for brackish water desalination: Upscaling the laboratory-scale device for standardised water supply on farms. Honours thesis, Murdoch University.

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Farmers in many places across Australia are facing drought, with dryland salinity in Western Australia one of the biggest concerns in the rural Wheatbelt farming industry. This project seeks to address the salinity issue and how to improve groundwater consumption while still providing suitable quality water for diverse farming needs.

The method investigated and used to solve this issue is the automation of a blending device with a solar PV-powered brackish water desalination unit by reverse osmosis membrane (PVRO). The plant used brackish water provided from the borewell on the farm at Muresk Institute near the Wheatbelt town of Northam and permeate water from the PVRO device. The selection switch can be used to blend different concentrations of total dissolved solids (TDS) to suit different on farm requirements. Water with different TDS concentrations can be used to either water the crops, distribute to the cattle or be used for domestic purposes.

In this study, data is presented to show that Solar PVRO permeate and brackish water can be automatically blended using the Arduino platform. The equipment used is listed in the Materials and Methods chapter and is utilised to give the best possible results within the budget constraints.

The possibility of having the blending unit would aid many farmers as it would promote more extensive use of the brackish water. Likewise, the blending unit will improve the long life of the RO membranes by not using RO as much. The unit is portable and moved easily to the required location.

By assisting the user in controlling the quality, the system can reduce the energy required in running the PVRO module by around 10 MW per year with savings of around $300 per year. More detail can be seen in Table 8.

This piece of equipment can assist not just farmers but regional communities with their basic water needs. The blending unit can decrease the RO water processed by around 34 %. This means that there is a water-saving of 170 L per hour, assuming the RO unit operates for five and a half hours per day. Additionally, total savings per year is around $1,069, including the earnings from electricity sell back. The important thing to note is that in this case, assumptions were that feed water is around 2,000 ppm, and the desired quality is 900 ppm. In another case, cost-saving would be different, as well as water savings.

In regard to membrane life expectancy, most manufacturers document the typical RO membrane to have a life expectancy of approximately seven years, in normal operation. Due to the 36 % reduction of permeate water, from the inclusion of the blending unit, an additional estimated 11.62 years of life expectancy can be gained to the RO membrane.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): Engineering and Energy
United Nations SDGs: Goal 6: Clean Water and Sanitation
Goal 7: Affordable and Clean Energy
Supervisor(s): Anda, Martin and Ravisankar, Vishnu
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