Preliminary Design of Water Intake System for In-situ Water Quality Assessment

Water quality at specific places is normally assessed by collecting water samples at site and transporting them to the laboratory for testing purposes. For in situ measurement, a popular method of collecting the samples is by using a conventional sample test kit such as syringe and cuvette. This approach, however, requires human intervention and needs to be done manually. The need for a mechanism to improve the sampling technique is crucial for in situ measurement such as for microfluidic and point-of-care devices. The aim of this work is to propose an intake system with the capability of controlling the samples that flow into the testing system. The circuit is designed and simulated using TinkerCAD software to observe and analyze the electrical characteristics of the proposed system in which a peristaltic pump is used as the main component in the intake system. Based on simulation work, 100 Omega rheostat setting between 10 to 50% was found to be suitable to drive a 12 V motor (representing a peristaltic pump) and satisfy the minimum operating current of 106.5 mA. The intake system was successfully developed to be capable of controlling the flow rate of intake samples through rheostat setting. At this range of rheostat setting, voltage characteristics for simulated and actual setup show similar patterns with less than 7% deviation. Through experiment, the system produced a range of flow rates between 0.842 ml(3)/s to 1.7549 ml(3)/s at controlling voltage from 6.2073 V to 10.5731 V. The relationship between the controlling voltage and flow intake was determined as a preliminary effort to develop a voltage-controlled intake system for multipurpose in situ application. Further improvement can be made by translating this voltage into its respective flow rate for display purposes and by integrating a commercial flow sensor for verification. This preliminary work could contribute to the future development of an intake system that is capable of performing a continuous and segmented automatic sampling to improve the traditional way of sampling process, which is manually done.