# Remote Water Quality Monitoring System for Use in Fairway Applications
## 2 Materials and Methods
### Remote Water Quality Monitoring System Architecture
* Integrated Sensors System  
The selection of appropriate sensors for monitoring water quality in waterways is critical to obtaining reliable data that will aid in assessing the aquatic environment, managing resources, and early detection of pollution. Key arguments justifying the choice of the parameters studied are presented below:  
* **Conductivity** measures water's ability to conduct electrical current, which can indicate the presence of chemical pollutants, dissolved salts, and heavy metals. Conductivity also reflects changes in the riverine ecosystem and potential threats to aquatic organisms, making it a crucial parameter for monitoring river water quality [29; 30]. * The **pH** level of river water is vital due to its impact on aquatic organisms and the chemical processes occurring in river ecosystems. pH plays a key role in the ability of organisms to adapt to environmental changes, influencing the solubility of chemicals, metabolic processes, and the overall structure of the aquatic ecosystem. It is also an indicator of the presence of toxic substances and the effects of anthropogenic factors on river water quality [29; 30; 31]. * **Temperature** monitoring is essential for understanding the biological, chemical, and physical processes within the river ecosystem. Temperature influences the solubility of gases, metabolic processes, the growth of aquatic organisms, seasonal changes, and the effects of anthropogenic impacts and climate change. It serves as a critical indicator for assessing the health of the river ecosystem and water quality [32; 33; 34; 35]. * The **dissolved oxygen** level in river water is crucial for sustaining aquatic life and assessing the health of the river ecosystem. Dissolved oxygen is essential for the respiration of aquatic organisms and serves as an indicator of water quality and the dynamics of biological, physical, and chemical processes. It is also a vital parameter for evaluating the effects of anthropogenic threats and climate change on river waters [36; 37; 38]. In the process of selecting sensors based on identified parameters, appropriate types of sensors were chosen. Various technologies were considered: both multi-parameter sensors, which measure multiple parameters simultaneously (e.g., conductivity and temperature) and single-parameter sensors. The selection of sensors took the following into account:  
* **Accuracy and sensitivity:** the ability to detect changes at low concentrations and provide precise measurements;
* **Environmental resistance:** durability in the face of temperature changes, humidity, sediment accumulation, and algae;
* **Versatility:** compatibility with wireless data transmission;
* **Cost-effectiveness:** the cost of purchasing, installing, maintaining, and servicing the sensors. Tests were conducted on various available sensors, focusing on the Gravity system sensors due to their versatility and full compatibility with Arduino. The following sensors were analyzed:  
Dissolved Oxygen Sensors: DFRobot Gravity--Analog Dissolved Oxygen Sensor X (SEN0237-A) (DFRobot, 63-640 Brain, Poland). Salinity Sensors: Gravity--Analog Salinity Sensor for Water and Soil (DFR0300-H), Gravity--Analog Electrical Conductivity Sensor for Solutions and Temperature PRO (SEN0451), and DFRobot Gravity--Analog Water Salinity Sensor (DFR0300). pH Sensors: DFRobot Gravity--Analog pH Sensor Pro V2, DFRobot Gravity--Analog pH Meter, and Gravity--Analog pH Meter V2 (SEN0161-V2). In this study, reference analyzers were utilized to enable both laboratory and field examination of the measured parameters, allowing for comparison with the values indicated by the sensors being tested. The analyzers employed were as follows:  
* **AZ86031 Water Parameter Analyzer:** This professional, portable meter is designed for the analysis of water parameters. It can measure pH, salinity, ion density in water (TDS), oxygenation, and conductivity. A key advantage of this analyzer is its ability to simultaneously use three probes.