Chinese
Spanish
French
Russian
German
Portuguese
Indonesian
Thai
Vietnamese
Arabic
High-salinity wastewater monitoring should track conductivity or salinity together with pH, temperature, flow and treatment-stage data; COD or other parameters are added according to the process and discharge objective. Conductivity is useful for salt-loading trends, but it does not identify individual ions or replace laboratory analysis. Buyers should define the wastewater source, expected range, materials compatibility, sampling point, cleaning access and PLC or SCADA requirements before selecting online sensors.
In recent years, the water pollution situation in China has become increasingly severe, and the research and application of water treatment technologies have become the focus of experts and scholars in related fields in China. Wastewater, especially industrial wastewater, mostly possesses the characteristics of high salinity. Direct discharge will bring great harm to the natural environment, causing pollution and increased salinity in natural water bodies, or leading to problems such as soil salinization and compaction. Since the salt content in high-salinity wastewater cannot be removed through natural biodegradation processes, the salt issue must be resolved during high-salinity wastewater treatment, or a solution must be sought after harmless treatment is conducted.
Analysis of Sources and Characteristics of Industrial High-Salinity Water
Industrial high-salinity water mainly originates from the coal chemical industry, pharmaceuticals, pesticides, and other industries, with salt content above 10,000 mg/L. There are many process nodes where industrial high-salinity water is generated, and it generally belongs to a class of wastewater characterized by high toxicity and refractory biodegradability. The main channels through which industrial wastewater is generated include: in industrial production, a large amount of water resources needs to be consumed. To reduce the consumption of water resources, recycling methods for water resources are commonly adopted within the industry, thereby forming high-salinity water; during the preparation of pharmaceuticals, pesticides, and their intermediates, processes such as the salting-out process, chemical synthesis, and acid-base neutralization will generate wastewater with relatively high salt content. Because this type of wastewater originates from product manufacturing, it usually carries along a large amount of raw materials, products, and impurities, so it also features high toxicity and refractory biodegradability. Overall, industrial high-salinity water has the characteristics of large discharge volume, wide range of sources, high salt content, and complex components, and the high-salinity water generated by different industries varies significantly.
For Engineering, Procurement, and Construction (EPC) contractors, system integrators, and automation control engineers, implementing an online water quality monitoring system is essential to accurately manage these complex streams and maintain continuous control loop reliability under harsh field conditions.
Analysis of Current Application Status, Advantages, and Disadvantages of High-Salinity Wastewater Treatment Technologies
Evaporation Technology
Evaporation technology for high-salinity water is generally targeted at high-salinity wastewater with a salt content above 40,000 mg/L. For low-concentration high-salinity water with a salt content of 1% to 4%, the salt removal efficiency of thermal evaporation is too low, making this technology unsuitable. Specifically, thermal evaporation technologies mainly include: multi-effect evaporation technology and mechanical vapor recompression technology. Multi-effect evaporation technology refers to the simultaneous use of multiple evaporation kettles connected in series, where hot steam passes through several evaporation kettles in sequence; the hot steam from the previous evaporation kettle then enters the next evaporation kettle to evaporate stage by stage, effectively utilizing the heat source to achieve the goal of high-salinity wastewater desalination. Mechanical vapor recompression technology, abbreviated as MVR technology, is a process that effectively utilizes heat sources with the help of a steam compressor. It obtains power through the recompression of steam and continuously reciprocates to improve the thermal efficiency of steam.
Evaporation technology can successfully separate the salt and water in wastewater, allowing them to be treated separately afterwards, which is a relatively thorough method for treating high-salinity wastewater. Therefore, this technology currently sees wide application in the coal chemical, pharmaceutical, and pesticide industries. However, for saline water with excessively high organic pollutant content, foaming is highly likely to occur during the evaporation process, causing material boil-over; at the same time, it may also affect the quality of the salt, resulting in the discharged salt carrying over too much organic matter, which still requires further treatment.
Membrane Treatment Technology
A membrane is a material with selective permeability that can achieve the purification, concentration, and separation of materials. Membrane pore sizes are generally on the micrometer scale, and are classified from largest to smallest into microfiltration, ultrafiltration, and nanofiltration. Membranes can be divided into pressure-driven and electrically-driven membranes based on differences in driving forces. Several types of membranes commonly used in industrial high-salinity wastewater treatment include: electrodialysis membranes and reverse osmosis membranes. Electrodialysis technology is currently relatively maturely developed; its traditional application modes are seawater desalination and industrial salt production, and its application in industrial wastewater is mainly concentrated in relatively clean coal chemical wastewater. Reverse osmosis technology was also originally applied to seawater desalination. Using it to treat industrial high-salinity wastewater incurs a relatively high cost, and since pollutants mostly exist in industrial high-salinity wastewater, it easily causes membrane fouling, which not only affects production efficiency but also leads to a reduction in membrane lifespan or even damage.
Biological Treatment Technology
The biological method treats pollutants contained in industrial high-salinity wastewater through microbial flora. The treatment cost is relatively low, but the conditions are strict; first of all, the salinity cannot be too high, otherwise it will exceed the tolerance range of the microorganisms, causing the treatment effect to be lost. Currently, biological treatment has been applied within a certain scope, and there are many salt-tolerant bacterial agents on the market; however, overall, biological methods still face certain problems in terms of microbial screening and stable engineering operation.
Future Development Trends of High-Salinity Wastewater Treatment Technologies
Application of Pretreatment Technologies
High-salinity water comes from numerous sources and has complex compositions; direct desalination or biological treatment cannot thoroughly resolve the problems. Therefore, many pretreatment technologies have been developed in recent years. Currently, harmless treatment technologies targeted at high-salinity water mainly include: physical adsorption, precision filtration, coagulation-flocculation, air flotation, catalytic wet oxidation, electrochemical oxidation, and supercritical water oxidation. For high-salinity wastewater containing refractory, toxic, and harmful substances, adopting the aforementioned methods can achieve the harmlessness of saline water, after which continuous desalination or diluted discharge can be performed to achieve the goal of thorough saline water treatment.
For high-salinity water containing only sodium chloride and sodium sulfate, after being processed by pretreatment technologies, the salt components become similar to seawater composition; those meeting the conditions can be discharged into the sea, or naturally discharged after dilution reaches emission standards. Pretreatment technology only treats toxic and harmful substances in the salt and does not affect the inorganic salt content, making direct discharge very promising. However, there are currently no very clear regulations, mainly considering that the removal of pollutants by this method is not completely thorough, and direct discharge still poses certain environmental risks, so it should be used with caution; but with the development of environmental protection treatment technologies and the gradual improvement of related regulations, it is believed that the destination problem of harmlessly treated saline water will be properly resolved in the future.
New Membrane Technologies
In addition to the previously mentioned membrane technologies, many new membrane technologies have emerged in environmental protection treatment in recent years, such as membrane distillation technology, which has now begun to be applied in high-salinity wastewater treatment. The application of new membrane technologies can not only achieve saline water treatment but also recover useful raw materials, intermediates, or products, showing a very promising future. In addition, due to the high production cost of membranes, its use in the high-salinity wastewater treatment industry is greatly limited; therefore, in the future, new membrane technologies will move towards directions with more and stronger functions, lower membrane production costs, and stronger anti-pollution capabilities.
Bioaugmentation Technology
Currently, biological treatment technologies are also applied, but because of problems with the strains themselves and insufficient process maturity, the application scope of biological treatment is localized. In the future, besides screening out salt-tolerant bacteria, it is also necessary to domesticate them to possess pollutant-degrading properties to enhance their treatment effects and expand their treatment scope.
In summary, industrial high-salinity wastewater treatment technology is currently developing very rapidly, and many technologies have already begun to be applied on a large scale with very good utilization effects. However, these technologies still have many shortcomings, such as: harmless treatment technologies and regulations are not yet complete, evaporation technology has not thoroughly resolved pollutant issues, the usage cost of the membrane method remains high, and the use of the biological method still faces large limitations. In future development, these technologies will become more and more complete, and the problem of high-salinity wastewater will surely be properly resolved.
Industrial Online Monitoring System Architecture
To ensure process optimization and data closed-loop control in automated sewage treatment plants, system integrators require an integrated architectural solution. Below is the multi-layer industrial IoT monitoring topology designed for continuous deployment:
[ Cloud Platform Layer: Smart Wastewater Management Platform / SCADA Center ] ▲ │ (Secure MQTT Stream via 4G LTE Gateway) ▼ [ Edge Control Layer: Local PLC (e.g., S7-1200) / Dosing Control Valves ] ▲ │ (RS485 Modbus RTU Protocol / Isolated Daisy-Chain) ▼ [ Field Sensor Layer: YexSensor Online Water Quality Sensors (IP68, 316L/Titanium) ]
By utilizing RS485 Modbus RTU networking, a single PLC communication module can poll multiple field digital sensors simultaneously, including industrial pH sensors, industrial dissolved oxygen sensors, and online COD monitoring instruments. This architecture replaces vulnerable analog loops with highly reliable, real-time data acquisition, delivering direct 4-20mA compatibility when legacy hardwired interlocks are required.
Product Parameters Section
| Parameter Specification | Technical Indicator |
|---|---|
| Communication | RS485 Modbus RTU (Dual isolated frontend) |
| Output Signal | RS485 / 4-20mA loop configurable |
| Power Supply | 12–24VDC (Reverse polarity protected) |
| Protection Rating | IP68 (Hermetically sealed submersed housing) |
| Operating Temperature | 0–50°C (High-temperature options available up to 90°C) |
| Pressure Range | ≤0.3MPa (Standard deployment; 0.6MPa optional) |
| Response Time | <30s (DSP digital moving average filter integrated) |
| Installation Method | Immersion / Pipe Mount via 3/4" NPT threads |
| Cleaning Method | Automatic Brush Optional (Motorized wiper block built-in) |
Industrial Project Selection Guide
When procuring instruments for high-fouling, high-salinity environmental engineering installations, procurement departments and engineering contractors must align the sensor specifications with the chemical background of the water type to minimize operational expenditure (OPEX):
Corrosive Ion Backgrounds: In chemical wastewater and desulfurization wastewater containing extreme $Cl^-$ levels, standard stainless steel is prone to pitting. Integrators should opt for a Titanium Alloy or POM housing from YexSensor's product range.
Fouling and Scaling Conditions: For biological treatment stages like MBR systems or aeration basins where biological films grow rapidly, selecting an automatic cleaning water quality sensor configuration is vital. The motorized wiper minimizes calibration frequency and extends the maintenance cycle from days to months.
System SCADA Wastewater Monitoring Compatibility: Ensure proper matching of PLC compatibility. For new telemetry remote water monitoring systems, select direct Modbus water quality sensor configurations to utilize full digital status register reporting, allowing remote diagnostic platform integration.
Field Deployment and Integration Best Practices
Based on real-world commissioning experience in industrial sewage treatment plants, proper electrical installation is essential to safeguard data stability and eliminate field bus disruptions:
Grounding and Shielding: The cable shield must be single-point grounded exclusively at the local PLC control cabinet end to prevent ground potential loop currents from destabilizing sensor microprocessors.
Anti-Interference Wiring: Maintain a minimum safety distance of 30cm between weak-signal RS485 lines and heavy 380VAC power cables running to recirculation or dosing pumps.
RS485 Termination Resistor: In long-distance field loops exceeding 100 meters, bridge a $120 Omega$ termination resistor across the A(+) and B(-) terminals at the furthest device node to avoid high-frequency signal reflections.
High-Salinity Wastewater Monitoring RFQ Checklist
Provide the industry and wastewater source, expected conductivity or salinity range, pH and temperature, organic and suspended-solids conditions, treatment stages, materials constraints, sampling point, cleaning access, cable distance, power, PLC or SCADA interface, alarm purpose, quantity and destination.
Review the online conductivity sensor and the industrial wastewater monitoring system. For project support, Send Your Project Requirements.
High-Salinity Wastewater Monitoring FAQ
Q1. Which parameters should be monitored in high-salinity wastewater?
A1. Conductivity or salinity, pH, temperature and flow are common core inputs. Add COD, turbidity, suspended solids, dissolved oxygen or other parameters only when they support a defined treatment, protection or discharge decision.
Q2. Can conductivity identify which salts are present?
A2. No. Conductivity indicates the water's overall ionic response and is useful for trends, but it does not identify individual ions. Use laboratory analysis when the project must determine salt composition or verify a regulatory method.
Q3. Where should sensors be installed in a high-salinity treatment process?
A3. Select representative points around feed equalization, concentration, membrane protection, evaporation or final discharge according to the control objective. Avoid stagnant zones, gas pockets and locations where crystallization or solids can bury the sensing surface.
Q4. How should material compatibility be checked?
A4. Provide the salt composition, concentration, pH, temperature, oxidants, solvents and cleaning chemicals to the supplier. Confirm wetted materials, seals, cable jacket and mounting hardware against the current model documentation before purchase.
Q5. How can monitoring support membrane or evaporation systems?
A5. Trend data can support feed review, concentration alarms, cleaning decisions and protection interlocks. Alarm thresholds must be established from the process design and commissioning data rather than copied from another plant.
Q6. What must be confirmed for PLC or SCADA integration?
A6. Confirm the output type, device address, baud rate, parity, register map, scaling, engineering units, polling interval, timeout behavior, grounding, termination and the alarm or interlock response required by the control narrative.
Q7. How should calibration and maintenance intervals be set?
A7. Base the interval on the water matrix, crystallization and fouling rate, required accuracy, process risk and the current sensor manual. Start with more frequent inspection during commissioning, record drift and cleaning results, then adjust the schedule using site evidence.
Q8. Can online monitoring determine the treatment technology by itself?
A8. No. Sensor data supports process selection and operation, but treatment design also requires laboratory characterization, mass balance, recovery targets, materials review, pilot testing where needed and assessment by the project engineer.
Q9. What information is required for a high-salinity wastewater monitoring quotation?
A9. Provide the wastewater source, expected parameter ranges, salt and chemical composition where available, process stages, installation point, materials constraints, cleaning access, power, communication protocol, alarm logic, quantity and destination.
Summary
High-salinity wastewater monitoring should combine conductivity or salinity with pH, temperature, flow and the additional parameters required by the treatment objective. Confirm the wastewater composition, expected ranges, wetted materials, installation point, fouling control, maintenance access, PLC or SCADA interface and complete RFQ inputs before procurement. Online data supports treatment operation but does not replace laboratory characterization or engineering design.
