What are the 5 methods of monitoring water quality?

A comprehensive description of the five main methods of monitoring water quality:

 1. Chemical analysis

Chemical analysis is a method of assessing water quality by quantitatively or qualitatively detecting various chemicals in water. It involves the use of specific chemical reagents to react with target substances in a water sample to produce measurable products or color changes to determine the concentration of those substances. Commonly used chemical parameters are pH, dissolved oxygen (DO), ammonia, total phosphorus and total nitrogen. In addition, advanced techniques such as colorimetry, multivariate analysis and high performance liquid chromatography (HPLC) are used for more complex constituent analyses.

- Advantages: Can provide highly accurate data for a wide range of water quality parameters.

- Disadvantages: Requires specialized laboratory equipment and technicians to operate, higher cost and longer time from sampling to results.

 2. Physical property testing method

Physical properties testing method involves the measurement of some basic physical properties of water, such as temperature, conductivity, turbidity, color, etc. These properties can directly reflect the water quality conditions. These properties can be a direct reflection of water quality, e.g., water temperature affects the rate of chemical reaction and dissolved oxygen content; turbidity indicates the amount of suspended particulate matter; and coloration may indicate the degree of organic contamination.

- Advantages: Some of the physical properties can be measured quickly in the field by portable instruments, which are relatively simple to operate.

- Disadvantages: While providing immediate information, they have limited ability to recognize complex contaminants.

 3. Microbiological assays

Microbiological tests are used to assess the degree of biological contamination of water by culturing and counting microorganisms in water samples, or by detecting the presence or absence of specific pathogens. Common tests include total coliforms and heat-resistant E. coli, which are important indicators for evaluating the sanitary status of water sources.

- Advantages: It is possible to visualize the presence of microorganisms in the water that are harmful to human health.

- Disadvantages: The operation process is cumbersome, requiring a certain amount of time and professional skills, and the cost is relatively high.

 4. Bioanalytical methods

Bioanalytical methods utilize the sensitivity of specific organisms to environmental changes as a tool for water quality monitoring. This involves observing the survival status, growth rate or behavioral changes of organisms in contact with the water sample to be tested. For example, certain phytoplankton, benthic animals and fish are very sensitive to changes in water quality and can be used as an early warning system for changes in water quality.

- Advantages: Provides information at the ecological level and helps to understand the impact of water quality on the ecosystem.

- Disadvantages: The experimental period is long and the accuracy is affected by a number of factors, such as the choice of biological species and the control of experimental conditions.

 5. Water Quality Sensor Approach

The water quality sensor method refers to the use of sensor technology to monitor water quality parameters in real time, such as temperature, pH, dissolved oxygen, conductivity, turbidity, and so on. The sensors can convert the detected physical or chemical signals into electrical signals, which in turn can be used in automated control systems or data logging. This method is particularly suitable for on-line monitoring and long-term surveillance, and can provide a continuous stream of data to help detect anomalies in a timely manner.

- Advantages: Easy to operate, suitable for large-scale and long-term water quality monitoring, cost-effective.

- Disadvantages: Sensors may be affected by environmental disturbances or aging and require regular calibration and maintenance.

 Application Scenarios and Suggestions for Selection

Different water quality monitoring methods have their own advantages and disadvantages, and the specific application needs to be decided according to the purpose of monitoring, budget constraints, immediacy of the required data, and the characteristics of the monitoring area. For example, for sudden pollution events, water quality monitoring by navigation (e.g., monitoring boat, monitoring vehicle) is particularly important because of its mobility; while for daily management and long-term trend analysis, it is more appropriate to build fixed automatic monitoring stations. At the same time, in order to ensure the accuracy and reliability of the monitoring results, they should be operated and analyzed in accordance with relevant regulations and standards.