Turbidity Explained

Turbidity measures the clarity of water by determining how much light passes through a water sample. Clear water has low turbidity, whereas murkier water murkier water has higher turbidity.

Turbidity measures the clarity of water by determining how much light passes through a water sample. Clear water has low turbidity, whereas murkier water murkier water has higher turbidity.

What is turbidity?

Turbidity measures the clarity of water by determining how much light passes through a water sample. Clear water has low turbidity, whereas murkier water indicates higher levels. This parameter is critical for assessing water quality, ecological health, and public safety.

Turbidity vs. Total Suspended Solids (TSS)

While turbidity measures water clarity, Total Suspended Solids (TSS) quantifies the actual particles in the water. These particles, which obstruct light, are primarily composed of dirt, silt, and organic matter. Generally, an increase in TSS leads to higher turbidity levels, affecting both visibility and the quality of the water. Water high in turbidity, or turbid water, can have any combination of materials in it, which in some cases makes water treatment necessary.

What causes turbidity? Detailed Causes

Turbid water can be caused by many different sources. Listed below are some of the common causes of turbidity:

  • Dirt
  • Silt
  • Organic matter
  • Bacteria
  • Pathogens
  • Microscopic organisms
  • Plant particles
  • Plankton

How do the above items get into the water? Well most of the time it has to do with human activity. Common events and activities (some of which we help treat before the water makes it to the environment) that can cause higher turbidity are:

  • Natural Processes: Rain, snowmelt, and erosion naturally introduce particles like silt and clay into water bodies.
  • Human Activities: Construction, mining, and agricultural runoff contribute significantly to water turbidity through the release of sediments and organic materials.
  • Industrial Discharges: Factories and treatment plants may discharge waste that increases turbidity, including organic pollutants and chemical residues.
  • Urban Runoff: Stormwater runoff from urban areas carries a mix of pollutants from roads, rooftops, and other surfaces into waterways.

Untreated wastewater is one of if not the biggest cause of turbidity levels rising in all bodies of water around the world. View our case studies page to learn how we help clean wastewater in many different industries.

How Do We Measure Turbidity?

Turbidity is measured using optoelectronic meters, specifically known as nephelometers or turbidimeters. But what is a turbidimeter? It's a type of instrument designed to evaluate how a light beam interacts with particles in a water sample. These devices emit a light source directly into the water, and sensors detect the amount of light that is scattered by the suspended particles. The degree of light scattering is a direct measure of the water's turbidity, quantified in Nephelometric Turbidity Units (NTU)—the more light is scattered or blocked, the higher the turbidity. Lower NTU values indicate clearer water, which is crucial for water quality, particularly in drinking water where turbidity should ideally be under 1 NTU. This measurement method is consistent and reliable, adhering to international standards such as ISO 7027 and EPA method 180.1, vital for regulatory compliance and water quality assessment. For educational settings on a budget, water test kits are available from the World Water Monitoring Challenge, providing an accessible option for understanding water clarity.

For low cost educational settings water test kits are available from World Water Monitoring Challenge.

A unit of turbidity measurement is a Nephelometric Turbidity Unit (NTU). The more the light is scattered or blocked during testing the higher the turbidity. Turbidity should ideally be under 1 NTU for drinking water.

Turbidity Standards and Regulations

Understanding and adhering to international standards for turbidity, such as ISO 7027 and EPA method 180.1, ensures reliable measurement and compliance with global water quality norms. These standards detail:

  • Methodology: Specific methodologies prescribed for turbidity measurements.
  • Equipment Specifications: Requirements for the equipment used in turbidity testing.

Advanced Turbidity Management Techniques

Managing turbidity effectively requires a combination of established methods and innovative technologies. Here, we explore some of the most impactful techniques and their applications in different settings:

1. Filtration Systems

  • Conventional Filtration: Detail how sand and charcoal filters are used in municipal water treatment facilities to reduce turbidity, including their maintenance requirements and efficacy.
  • Membrane Filtration: Discuss the use of microfiltration, ultrafiltration, and reverse osmosis membranes that provide higher filtration accuracy, capable of removing smaller particulates that contribute to turbidity.
  • Advanced Media Filters: Introduce newer media types such as glass and advanced polymers that offer improved performance over traditional sand filters in terms of particle size retention and filter longevity.

2. Sedimentation Techniques

  • Clarifiers and Settling Tanks: Explain the role of gravity in settling out heavier particles before the water passes through finer filters, reducing the load on downstream systems.
  • Chemical Flocculation: Expand on the use of coagulants that bind with suspended particles, making them heavier and faster to settle. Discuss the types of chemicals used and their impact on water quality.

3. Constructed Wetlands

  • Natural Filtration: Describe how constructed wetlands mimic natural water purification processes, using vegetation and naturally occurring microorganisms to reduce turbidity. Highlight specific plant species known for their water-cleansing properties.
  • Design and Implementation: Offer insights into the planning and construction of these wetlands, including spatial requirements, typical costs, and maintenance challenges.

4. Alternative Methods

  • Ultraviolet Light Treatment: Though primarily used for disinfection, explain how UV can also impact certain types of turbidity, particularly those involving microbial contaminants.
  • Magnetic Separation: Introduce emerging technologies that use magnetic fields to remove iron-based particles from water, providing a novel way to address specific turbidity issues.

5. Real-World Applications and Success Stories

  • Provide case studies where these advanced techniques have been successfully implemented. For example, showcase a city that has combined membrane filtration with constructed wetlands to achieve exceptionally low turbidity levels.
  • Discuss the role of community involvement and education in maintaining these systems and ensuring they continue to perform optimally over time.

Ecological Impacts of Turbidity on Aquatic Ecosystems

Turbidity can influence aquatic ecosystems. High turbidity levels can reduce the amount of sunlight penetrating the water, which is crucial for photosynthesis in aquatic plants and algae. This reduction in sunlight can lead to decreased oxygen production, which is important for aquatic life. When plants produce less oxygen it can disrupt the food chain at its most fundamental level.

Also, suspended particles in turbid water can smother benthic habitats (the ecological region at the lowest level of a body of water such as the substrate of a lake or ocean), where many small organisms live and larger species find food. This sedimentation can lead to habitat degradation, affecting species that rely on clear water for breeding and feeding, such as fish and amphibians. For instance, many fish species require specific conditions for spawning, and increased sediment can bury eggs and reduce hatch rates, impacting future population sizes.

Addressing these ecological impacts involves implementing comprehensive water management strategies that not only focus on reducing turbidity but also on preserving the health of aquatic ecosystems. Through concerted efforts involving regulation, community engagement, and the adoption of advanced technologies, significant progress can be made in mitigating the negative effects of turbidity on our waterways.

Is turbidity or cloudy water dangerous?

High turbidity in drinking water does not look right, and may also cause health issues for anyone who drinks that water. Many times (just like in nature above) more turbidity allows pathogens to grow in the water. It allows these microorganisms to feed and shelter from direct sunlight and other disinfectants, which would kill them. The systems we build and your town uses to clean your drinking water should help remove turbidity completely so this is not a worry of yours. At the end of the day it is not always the turbidity that is the cause of concern in drinking water, but many times that something else could be hiding within.

High turbidity out in the environment is also dangerous for ecosystems and many animal species. The cloudy water can cause diminished food supplies for fish and other aqua based creatures. The particles in the water can also cause the fish to get sick, not grow as large, impact spawning grounds, impact fertility, and more.

Future Challenges and Innovations in Turbidity Control

Exploring future challenges in managing turbidity and the potential innovations could provide insights into the evolving landscape of water quality management. Discussion might cover:

  • Emerging Technologies: Potential new technologies for more accurate and efficient turbidity measurement and control.
  • Regulatory Changes: How evolving regulations might shape future approaches to managing turbidity in various industries.


Turbidity is a key indicator of water quality and ecological health. By understanding its causes, measuring techniques, and management methods, we can better protect water resources and ensure safe water for all uses. Continued research and innovation will play vital roles in addressing the challenges associated with turbidity in water bodies around the globe.

by Reid Burns

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