Testing of a laboratory-scale automated blending device for Fit-For-Purpose water supply from a small scale reverse osmosis system for farms

With the continuous trend of drying climate it has become evident that water scarcity is becoming a bigger issue then it was decades ago. It is particularly affecting isolated settlements such WA’s farmlands, which are in need of essential water supply and are far away from the main cities. Therefore, an alternative water supply solution was to implement a small-scale RO unit with the integration of an automated blending device, as the combination of the two sources (permeate & feed) increases the volume of existing water supply at a much-reduced cost. This thesis project involves the redevelopment of a bench scale-blending device to further optimise the performance of the device by testing two control strategies developed to enhance the effectiveness of the device in achieving the end user’s desires. The developed and tested control strategies were the Bang Bang control strategy and the Time-Proportional PID control strategy that was constructed using a software known as the Arduino IDE. Three main tests that were conducted including a Precision & Accuracy test; the Speed test and the Setpoint Change Tracking Ability test, which assess the ability of the program to meet the desired objectives. The findings of the trials carried out evaluated that each control strategy has its own advantages and disadvantages. Therefore, to determine the “better” strategy of the two depends on the end user (farmer) of the device and the setting in which the device will be implemented. It was concluded that the Bang Bang control strategy was most suitable for short-term use due to its switching mechanism of the solenoids and that the Time-Proportional PID control strategy was more preferable for long-term application. However, for this device to be tested on field scale it requires further research to be done on the different blending techniques suitable for this context as the current blending technique employed will not be adequate for an onsite application