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Designing an on-farm evaporation pond for the wheatbelt, Western Australia

Dabeedooal, Neetesha (2018) Designing an on-farm evaporation pond for the wheatbelt, Western Australia. Honours thesis, Murdoch University.

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Abstract

An evaporation pond is a lined basin where wastewater is disposed to decrease the volume of water in it. Rejected brine is the by-product waste produced from water treatment technologies. The conventional evaporation pond is used to evaporate the brine solution through solar radiation and wind. It is mainly used in countries with dry and warm weather such as Saudi Arabia and it can be utilised in regions far from the seas. The rejected brine is easily dumped into the sea if the site is located near to the coast. The volume of effluent is reduced due to evaporation process making the solution more saline.

The Goldfields and Agricultural Water Supply Scheme (GAWS) is a very expensive water supply option for the Wheatbelt region in Western Australia. Therefore, Water Corporation has launched Farmland Alternative Water Supply Project to look for an alternative water supply option. Groundwater salinity is a big issue in Australia and this affects the productivity and income of farmers. Different water treatment technologies such as Reverse Osmosis/Nano Filtration (RO/NF), solar distillation and phytodesalination are used to treat groundwater and therefore, evaporation pond is constructed to manage the brine. The focus in this project is to design an evaporation pond.

Site selection is a major role before designing an evaporation pond. Salinity can be measured by using an electrical conductivity. In the project, Bakers Hill is considered and the salinity level at the site is approximately 3000-7000mg/L. The three main factors to design an evaporation pond is pond depth, pod area and pond evaporation and all the formulae are obtained from literature. The pond area depends on annual brine inflow, groundwater salinity and the Potential Net Evaporative Loss. After calculating the Potential Net Evaporative Loss, the area of basin for 100ML/year inflow can be obtained from the salinity curves and with the given information, the area of the required basin is gained.

From the results, a barchart of the monthly mean rainfall and the monthly evapotranspiration were plotted. It is noticed that there is less rain during summer than in winter season. The annual rainfall at Bakers Hilll is approximately 589.4 mm and the annual evapotranspiration is about 1732.4mm. At the beginning of the year, evaporation rate is very high because the solar radiation intensity is higher during summer compared to during winter. In the months of June until August, the Potential Net Evaporative Loss is negative because rainfall records are greater than evaporation rate. An interpolation is done to find the basin area for 100ML/year inflow at a specific Potential Net Evaporative Loss. Area of required basin is calculated by using the formula from literature. The parameters can be varying to have a proper sizing of the evaporation pond. A user manual is written for the design spreadsheet model for the farmers to follow on how to use it.

The results obtained are compared to data from literature. Two designed spreadsheets are obtained from internet resources. They are different from the one I have designed because the main parameters are not assumed but they are calculated using formula from literatures. Similar trend results were obtained from both spreadsheets.

After designing the pond, some recommendations are made to improve the designed evaporation pond. Deeper pond can be used to reduce evaporation rate. Spray evaporators is suggested to enhance evaporation rate and Wind Aided Intensified Evaporation (WAIV) can be an alternative solution for brine management instead of using conventional evaporation pond.

In this study, a Microsoft Excel spreadsheet is developed to help local people and farmers design an evaporation pond in an inland region and manage rejected brine. The formulae for each parameter are provided in the spreadsheet and farmers do not need to calculate or design them. Some factors including mean rainfall, evapotranspiration and solar radiation obtained from the Bureau of Meteorology (BOM), annual brine inflow and groundwater salinity were taken into consideration.

Item Type: Thesis (Honours)
Murdoch Affiliation: School of Engineering and Information Technology
Supervisor(s): Ela, Wendell
URI: http://researchrepository.murdoch.edu.au/id/eprint/41906
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