Water turbidity: why monitor it and how to measure it effectively
What is turbidity and why it’s a key indicator
Turbidity is a critical parameter in water quality assessment. It refers to the cloudy appearance of water caused by suspended particles such as sediments, organic matter, or certain pollutants that can compromise quality. Monitoring turbidity is therefore essential to ensure compliance with regulatory standards and to optimize treatment processes, whether for drinking water, wastewater, or industrial effluents.
In this article, we’ll explore the challenges linked to turbidity, regulatory requirements, and the methods used to measure it effectively.
Why measuring turbidity matters for water quality
Unlike other indicators, turbidity is based on a physical principle: the scattering of light. It provides an instant snapshot of water purity and serves as a valuable tool for environmental monitoring and treatment plant control.
High turbidity can deteriorate the bacteriological quality of water, interfere with treatment processes, and disrupt aquatic ecosystems. It can also hide the presence of harmful microorganisms.
Turbidity can be monitored continuously to anticipate rapid fluctuations, or periodically for routine checks, audits, or isolated sites.
Turbidity vs. TSS (total suspended solids)
Although often related, turbidity and total suspended solids (TSS) are two distinct parameters. Turbidity measures water’s ability to scatter light, while TSS quantifies the actual mass of particles in a given volume. Their relationship depends on particle size, type, and refraction, meaning two samples of water may produce very different results.
Monitoring turbidity across different environments
Turbidity is widely used as an indicator of water quality in many applications. Whether in drinking water, wastewater, natural waters, or industrial effluents, it helps anticipate sanitary, environmental, and technical risks.
Turbidity in natural waters
Turbidity is a reliable indicator of soil erosion and diffuse pollution linked to runoff, especially after heavy rainfall.
In natural waters, high turbidity is caused by large concentrations of suspended particles. These block light penetration, disrupting photosynthesis in aquatic plants, reducing dissolved oxygen levels, and ultimately destabilizing ecosystems.
There is also a direct link with drinking water management. During heavy rain, turbidity levels rise significantly, complicating treatment stages. Monitoring turbidity helps anticipate these variations and safeguard water quality.
Measuring and monitoring turbidity in drinking water
Suspended particles in drinking water can promote the growth of pathogens such as bacteria, viruses, and parasites, which may cause disease. High turbidity often masks their presence and reduces the effectiveness of disinfection treatments such as chlorine or UV.
As seen earlier, high turbidity overloads treatment systems, making purification more complex and costly. Particles clog filters and increase chemical consumption, driving up operating costs.
From a regulatory perspective, the WHO recommends turbidity levels below 5 NTU. However, most countries set stricter limits: a maximum of 1 NTU, and often less than 0.3 NTU after filtration to ensure safe drinking water.
Turbidity control in wastewater treatment
In wastewater treatment plants, turbidity is a key performance indicator. It helps detect sedimentation failures, hydraulic overloads, or filter clogging before TSS levels even increase. Rising turbidity can also indicate incorrect reagent dosing, sludge loss, or equipment malfunction.
By measuring turbidity, operators can instantly adjust processes, avoid exceeding discharge thresholds, and ensure regulatory compliance.
It is an effective tool for monitoring treatment stability, easily integrated into supervisory systems and enabling automated alerts.
Impact of turbidity on industrial waters
In industrial settings, suspended solids accelerate pipe fouling, pump wear, and cooling system failures. This leads to higher maintenance costs and increased energy consumption.
In agriculture, irrigation water quality is also affected. High turbidity can clog filters and sprinklers, and over time, degrade soil structure and crop health.
How to measure water turbidity accurately
Nephelometric technology
Nephelometric measurement is the most widely used method for monitoring turbidity. It is based on detecting light scattered at a 90° angle by suspended particles when a light beam passes through the sample. Defined by ISO 7027, this method uses infrared light to minimize color interference. Results are expressed in NTU units.
Turbidity sensors for real-time monitoring
Turbidity sensors use the nephelometric method to provide real-time measurements by being directly integrated into pipes or tanks. Data is transmitted wirelessly, allowing operators to instantly adjust treatment parameters. Sensors help detect anomalies early and simplify process management.
Other evaluation methods
In some cases, turbidity can be visually assessed using a Secchi disk, commonly in natural waters, or with turbidity tubes. Water samples may also be analyzed in laboratories for advanced testing, including spectrophotometry.
Aqualabo solutions for turbidity monitoring and control
As a specialist in water quality analysis and monitoring, Aqualabo designs and manufactures robust, precise instruments adapted to the most demanding environments. Our expertise is backed by more than 70 years of innovation dedicated to water quality.
Turbidity sensors
LowTuS turbidimeter
Developed with over 70 years of expertise, the LowTuS uses 90° infrared light scattering (ISO 7027) for precise measurements across ranges of 0–10 NTU and 0–100 NTU. Its automatic cleaning system prevents contamination build-up, ensuring consistent reliability.
Key features:
- Nephelometric 90° scattering method – ISO 7027
- Ranges: 0–10 NTU; 0–100 NTU
- Digital Modbus RS-485 communication
- Automatic optical cell cleaning
Quick check with solid tare
Applications: Raw water, drinking water process control, distribution network monitoring, filtered water
NTU sensor
Covering an extended range up to 4000 NTU, this sensor stands out for its robustness, precision, and compatibility with demanding environments. Digital communication, strong resistance, and integrated transmitter make it a reliable choice for optimal water management.
Key features:
- Infrared fiber optic technology
- Ranges: 0–4000 NTU or 0–4500 mg/L
- Robust and waterproof (IP68)
- Ultra-low power consumption
Optional HYDROCLEAN automatic cleaning
Applications: Municipal wastewater treatment (inlet/outlet), sewer network load monitoring, industrial effluent treatment, surface water monitoring, dredging operations, drinking water pumping
MES5 sensor
The MES5 sensor measures both suspended solids and turbidity using infrared absorptiometry, ensuring accuracy and reliability across various water treatment applications.
Key features:
- IR optical sensor with absorptiometry technology
- Ranges: TSS 0–50 g/L, sludge blanket 0–100%, turbidity 0–4000 FAU
- Digital communication Modbus RS-485 / SDI-12
Robust construction
Applications: Municipal wastewater treatment (inlet, aeration basin, clarifier, outlet), industrial effluent treatment, sludge treatment lines, dredging site monitoring
Portable monoparameter
NEON Portable Turbidity meter
The portable NEON NTU device, equipped with a turbidity sensor (ISO 7027 nephelometric method), measures temperature, turbidity (NTU/FNU), and turbidity in mg/L. Compact, modern, and intuitive, it records up to 30,000 data points, downloadable via Wi-Fi.
Key features:
- User-friendly, quick setup
- Robust, waterproof (IP67), lightweight
- Digital sensor technology for reliable measurements
- Data logging and wireless transfer via Wi-Fi
Applications: Municipal wastewater treatment, sewer network monitoring, industrial effluent control, surface water surveillance, dredging operations
For more information about our solutions or to request a personalized quote, contact our team today via our online form :
