How to monitor water quality during pure wastewater treatment process?

How to monitor water quality during pure wastewater treatment process?

In the field of pure wastewater treatment, ensuring that the treated water quality meets specific standards is the core goal. As the "eyes" of the entire treatment process, water quality monitoring can provide real-time feedback on the treatment effect, detect potential problems in a timely manner, and ensure the stable operation of the treatment process. So, how to scientifically and effectively monitor water quality in the process of pure wastewater treatment? This requires exploration from multiple dimensions, including the determination of monitoring indicators, selection of monitoring methods, setting of monitoring frequency, and management and application of data.

1、 Clarify water quality monitoring indicators

Different scenarios and application requirements for pure wastewater treatment correspond to different key monitoring indicators. From the perspective of physical properties, water temperature, turbidity, and chromaticity are fundamental indicators. Water temperature can affect the reaction rate of chemical and biological treatment processes, and excessively high or low water temperature may inhibit microbial activity or reduce chemical reaction efficiency; Turbidity reflects the content of suspended particles in water, and high turbidity means that there are many impurities in the water, which may affect the effectiveness of subsequent treatment processes; Chromaticity intuitively reflects the color condition of water. If some colored substances in industrial wastewater are not effectively removed, they not only affect the appearance but may also contain harmful substances.

In terms of chemical indicators, pH is an important parameter that affects the form of substances in water and the direction of chemical reactions. For example, in acidic environments, the solubility of certain heavy metal ions increases, while in alkaline conditions, precipitation may form. Chemical oxygen demand (COD) and biochemical oxygen demand (BOD) are used to measure the content of organic matter in water. COD reflects the degree of pollution caused by reducing substances in water, while BOD represents the amount of dissolved oxygen consumed by microorganisms to decompose organic matter in water. The high or low values of the two directly reflect the level of organic pollution in wastewater. In addition, nutrient indicators such as ammonia nitrogen, total phosphorus, and total nitrogen, as well as the content of heavy metal ions (such as lead, mercury, cadmium, etc.) and specific organic pollutants (such as benzene derivatives and phenols), are also the focus of monitoring. If these substances are discharged beyond the standard, they will cause serious harm to the ecological environment and human health.

Microbial indicators cannot be ignored, such as the total number of bacteria and the number of Escherichia coli, which can reflect the pollution status of microorganisms in water. These indicators are crucial for drinking water treatment and some industrial water treatment with strict requirements for microorganisms.

2、 Choose appropriate monitoring methods

（1） Laboratory analysis methods

Laboratory analysis is a traditional and precise method for water quality monitoring. For the determination of chemical indicators, such as COD, the potassium dichromate method is often used, which oxidizes organic matter in water with a strong oxidant and calculates the COD value based on the amount of oxidant consumed; BOD determination generally adopts a five-day cultivation method, in which water samples are cultured at a specific temperature for five days, and the difference in dissolved oxygen before and after measurement is used to determine the BOD value. The detection of heavy metal ions can be achieved through methods such as atomic absorption spectroscopy and atomic fluorescence spectroscopy, which can accurately determine trace amounts of heavy metal elements. For microbial indicators, methods such as plate counting and multi tube fermentation are commonly used to isolate, culture, and count microorganisms in water samples in a laboratory environment. Although laboratory analysis methods yield accurate results, they have drawbacks such as long processing times, complex operations, and the need for professional personnel and equipment.

（2） Online monitoring technology

With the development of technology, online monitoring technology has gradually become mainstream. An online pH meter can monitor the acidity and alkalinity of water in real time. Through a battery composed of a glass electrode and a reference electrode, the acidity and alkalinity of the solution are converted into electrical signals for output; The online turbidity meter utilizes the principle of light scattering. When light passes through a water sample, suspended particles in the water scatter the light, and the turbidity is determined by measuring the intensity of the scattered light; The online COD monitor uses spectrophotometry or electrochemical methods to continuously and automatically monitor the COD concentration in water. Online monitoring technology has the advantages of strong real-time performance, fast data updates, and remote monitoring, which can timely detect changes in water quality and provide a basis for adjusting treatment processes. However, some online monitoring equipment has problems such as high maintenance costs and monitoring accuracy affected by environmental factors.

3、 Reasonably set monitoring frequency

The setting of monitoring frequency requires comprehensive consideration of factors such as the characteristics of wastewater treatment processes, water quality stability, and treatment scale. For pure wastewater treatment systems with relatively simple treatment processes and stable water quality, the monitoring frequency can be appropriately reduced, such as conducting routine indicator monitoring once a day or every shift, and conducting comprehensive indicator testing once a week. For the treatment of complex industrial wastewater or treatment systems with extremely high water quality requirements, such as the ultra pure water preparation system in the electronic chip manufacturing industry, it is necessary to increase the monitoring frequency. Conventional indicators may need to be monitored online in real time, and key indicators may be tested every hour or even every half hour to detect water quality fluctuations in a timely manner and take measures. In addition, after handling system startup, shutdown, process adjustment, or equipment failure repair, monitoring frequency should be increased to ensure that water quality returns to stability as soon as possible.

4、 Management and Application of Water Quality Monitoring Data

The effective management and application of water quality monitoring data is the key to playing a monitoring role. Firstly, it is necessary to establish a comprehensive data recording and storage system. Whether it is laboratory analysis data or online monitoring data, accurate information such as sampling time, monitoring location, monitoring indicator values, monitoring personnel, etc. should be recorded and classified for storage, facilitating subsequent queries and analysis. Use data analysis software to process monitoring data, draw trend charts, comparison charts, etc., and visually display the patterns of water quality changes. For example, by plotting the trend of COD concentration over time, it is possible to determine whether the removal efficiency of organic matter by the treatment process is stable; Comparing water quality indicators at different treatment stages can evaluate the treatment efficiency of each treatment unit.

Adjust the processing parameters in a timely manner based on the analysis results of monitoring data. If the removal effect of ammonia nitrogen is found to be poor, the aeration time can be appropriately increased or the sludge concentration of the biological treatment unit can be adjusted; If the heavy metal ions exceed the standard, the dosage and reaction conditions of the chemical precipitant can be optimized. At the same time, monitoring data will be used to optimize and improve the processing technology. Through long-term data accumulation and analysis, weak links in the processing technology will be identified, providing a basis for technological upgrading and equipment transformation. In addition, monitoring data is also an important basis for companies to report water quality to environmental protection departments and accept supervision. Ensuring the authenticity and completeness of data helps companies fulfill their environmental responsibilities.

Water quality monitoring in the process of pure wastewater treatment is a systematic work, from indicator determination, method selection, frequency setting to data management application, each link is interrelated and indispensable. Only by establishing a scientifically sound water quality monitoring system can we timely and accurately grasp the water quality status, ensure the efficient and stable operation of the pure wastewater treatment system, and achieve water quality standards and sustainable utilization of water resources.

The above content comprehensively introduces the key points of water quality monitoring in the process of pure wastewater treatment. If you would like to further understand the monitoring details of a certain type of monitoring indicator, or are interested in the analysis methods of monitoring data, please feel free to communicate at any time.