Abstract
Recently, environmental pollution resulting from industrial waste has been emerging in an endless stream. The industrial waste contains chemical materials, heavy metal ions, and other toxic materials. Once the industrial waste is discharged without standards, it might lead to water or environmental pollution. Hence, it has become more important to provide evidence-based water quality monitoring. The use of a multifunctional miniaturized water quality monitoring system (WQMS), that contains continuous monitoring, water quality monitoring, and wireless communication applications, simultaneously, is infrequent. Thus, electrodes integrated with polydimethylsiloxane flow channels were presented in this study to be a compound sensor, and the sensor can be adopted concurrently to measure temperature, pH, electrical conductivity, and copper ion concentration, whose sensitivities are determined as 0.0193 °C/mV, −0.0642 pH/mV, 1.1008 mS/V·cm (from 0 mS/cm to 2 mS/cm) and 1.1975 mS/V·cm (from 2 mS/cm to 5.07 mS/cm), and 0.0111 ppm/mV, respectively. A LoRa shield connected into the system could provide support as a node of long range wide area network (LoRaWAN) for wireless communication application. As mentioned above, the sensors, LoRa, and circuit have been integrated in this study to a continuous monitoring system, WQMS. The advantages of the multifunctional miniaturized WQMS are low cost, small size, easy maintenance, continuous sampling and long-term monitoring for many days. Every tested period is 180 min, and the measured rate is 5 times per 20 min. The feedback signals of the miniaturized WQMS and measured values of the instrument were obtained to compare the difference. In the measured results at three different place-to-place locations the errors of electrical conductivity are 0.051 mS/cm, 0.106 mS/cm, and 0.092 mS/cm, respectively. The errors of pH are 0.68, 0.87, and 0.56, respectively. The errors of temperature are 0.311 °C, 0.252 °C, and 0.304 °C, respectively. The errors of copper ion concentration are 0.051 ppm, 0.058 ppm, 0.050 ppm, respectively.
Highlights
Industrial waste contains toxic substances such as chemical substances, which cause water and environmental pollution
Once the industrial waste is discharged without standards, it might lead to water or environmental pollution
It has become more important to inquire into water quality monitoring
Summary
Industrial waste contains toxic substances such as chemical substances, which cause water and environmental pollution. Once the industrial waste is discharged without standards, it might lead to water or environmental pollution. It has become more important to inquire into water quality monitoring. With the progress of semiconductor, large data processing, and wireless communication technologies, a miniaturized water quality monitoring system (WQMS) could be developed in this study. In order to identify the level of water pollution, water quality indicators are used to analysis the water properties: physical (e.g., temperature, odor, turbidity, and electrical conductivity), chemical. The water temperature indirectly affects some measured standards of the indicators, such as electrical conductivity, dissolved oxygen, and so on. Acidity is called the pH value, which is the hydrogen ion concentration in water. It can be used to determine whether water is polluted or to what extent saltwater infusion occurs in a coastal area
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