Turbidity Explained

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.

What causes turbidity? Detailed Causes

Turbid water can arise from various sources, often tied to both natural processes and human activities. Here are some common causes of turbidity:

• Dirt
• Silt
• Organic Matter
• Bacteria
• Pathogens
• Microscopic Organisms
• Plant Particles
• Plankton

How Do These Items Get Into the Water?

Natural Processes

• Rain and Snowmelt: Precipitation and melting snow can carry silt, clay, and other particles into water bodies.
• Erosion: The natural wearing away of soil and rock introduces particles into rivers, lakes, and streams.

Human Activities

• Construction: Building projects disturb the soil, releasing sediments into nearby water bodies.
• Mining: Extractive processes displace earth, contributing to sediment runoff.
• Agricultural Runoff: Farming activities can wash soil, fertilizers, and organic materials into waterways.
• Wastewater: Untreated wastewater is one of the biggest contributors to rising turbidity levels in water bodies worldwide, introducing various suspended solids and organic materials. Because of this, it is important to think about turbidity in wastewater treatment.

Industrial Discharges

• Factories and Treatment Plants: These facilities may release waste that increases turbidity, including organic pollutants and chemical residues.

Urban Runoff

• Stormwater: Rainfall in urban areas picks up pollutants from roads, rooftops, and other surfaces, carrying them into water systems.

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 more particles there are, the more they scatter light in the water. 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.

A simpler, historical method still widely used today is the Secchi disk—a circular plate divided into black and white quadrants, typically 20 cm (8 inches) in diameter. Named after Pietro Angelo Secchi who first used it in 1865, this disk is lowered into water until it's no longer visible. The depth at which the disk disappears, known as the Secchi depth, provides a practical measure of water clarity. While less precise than electronic turbidimeters, Secchi disks remain valuable tools for long-term monitoring of lakes and oceans, offering a cost-effective way to track changes in water clarity over time. They're particularly useful in citizen science programs and educational settings, as they provide immediate, visual feedback about water quality conditions.

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). This means when you use a measuring device to get turbidity readings, you would get the readings in NTUs. The more the light is scattered or blocked during testing the higher the turbidity. Turbidity should ideally be under 1 NTU for drinking water. Now you should know how to test turbidity of water. If you have any questions reach out to us.

Turbidity's Relation to Total Suspended Solids (TSS)

• Turbidity: Measures the clarity of water by assessing how much light can pass through it. Higher turbidity means murkier water.
• Total Suspended Solids (TSS): Quantifies the actual particles suspended in the water, such as dirt, silt, and organic matter.

While turbidity indicates how clear or cloudy the water is, TSS provides a direct measurement of the concentration of suspended particles. Generally, higher levels of TSS result in higher turbidity, impacting both visibility and overall water quality.

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.
• Membrane Bioreactors: This type of membrane filtration can also help reduce the turbidity in a water stream.

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.

‍

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.

‍

Conclusion

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.

‍