Justin Wilkens
Turbidity is a standard measurement utilized in wastewater treatment. Cloudy water can indicate the presence of disease, microorganisms, and pollutants that pose risks to public well-being. This parameter can also be used to evaluate the effectiveness of a filtration process.
What Is Turbidity?
In simplest terms, turbidity refers to the relative clarity or cloudiness of a liquid. This visual characteristic measures how much light passes through a sample—the clearer the water, the lower the turbidity, and vice versa.
Various materials can impact turbidity, including both organic and man-made matter. In terms of public health, this parameter is important for assessing drinking water quality and safety.
Turbidity v. Total Suspended Solids
Turbidity is the measurement of water clarity, whereas total suspended solids (TSS) are the materials that affect turbidity. Essentially, high levels of suspended solids will naturally lead to a cloudier liquid.
What Causes Turbidity?
Turbidity can occur for many reasons. Depending on the location, a water source may be susceptible to mainly natural or human-influenced pollutants. Other times, a combination of factors can worsen water quality.
Natural Processes
Many microorganisms, animals, and weather conditions can lead to excessive cloudiness. Rivers, lakes, and streams are especially at risk of sediment disruption, as other bodies of water collect and redistribute sediment to new locations.
Potential natural causes of turbidity include:
- Weather conditions: Runoff from extreme precipitation, snowmelt, or storms can cloud water. Windstorms and other weather-related conditions can also disrupt sediment, resulting in higher turbidity.
- Erosion: Water currents can collect mud, dirt, and rock while flowing through eroded areas.
- Decaying organic matter: Decomposing plant and organic particles can result in tea-colored water or algal blooms that reduce clarity.
- Algae: As algae die and decompose, they release organic matter into water, leading to higher levels of turbidity. Large quantities of phytoplankton can also turn water a reddish-brown color.
- Wildfires: Wood ash from wildfires can muddle water sources.
Human & Industrial Sources
Human influences are another major contributor to turbidity levels. Whether from farms or factory plants, excess runoff can negatively impact quality by introducing various chemicals, pollutants, and fertilizers into water sources.
Below are common inorganic sources of turbidity:
- Agricultural runoff: Fertilizers, organic materials, soil, and other chemical runoff from farms can infiltrate nearby water sources, resulting in heightened turbidity.
- Mining: As with agricultural practices, excavation can discharge excessive mud and sediment into bodies of water.
- Urban runoff: Stormwater from cities and towns can pollute water sources with chemicals, pavement fragments, building materials, and other particles.
- Wastewater discharge: Poorly treated wastewater may harbor residual pathogens, contaminants, and pollutants. Thus, discharged waste from treatment plants can raise turbidity in bodies of water.
How Turbidity Is Measured
Typically, optoelectronic meters (e.g., nephelometers or turbidimeters) measure the turbidity of water. These tools emit light into a liquid to evaluate how particles interact with the beam. The amount of light scattered is calculated in Nephelometric Turbidity units (NTU), with higher NTUs indicating increased turbidity levels. Low readings, ideally under 1 NTU, suggest water is safe for drinking.
Below are the potential effects of high turbidity and suspended solids levels:
- Decreased oxygen levels in water
- Clogged fish gills
- Decreased light penetration in water, leading to lower aquatic plant growth
- Reduced resistance to disease in fish
- Altered egg and larval development
- Excessive algae growth
- Hindered visibility, allowing fish to fall prey to predators
- Smothered benthic habitats
- Limited area for fish spawning and burying eggs
Human health impacts
- Waterborne disease outbreaks
- Exposure to microbes, bacteria, viruses, and parasites
- Poor taste or odor of water
- Stomach upset, such as nausea, cramps, or diarrhea
How Is Turbidity Managed?
Addressing high turbidity in water requires a multifaceted approach. Management may involve various TSS management methods depending on the location, available resources, and treatment facility size.
Here are common techniques used to manage turbidity levels:
- Coagulation-flocculation: A coagulant encourages particles to flocculate and settle. The resulting sludge collects at the bottom of a basin before being removed from the water before filtration.
- Settling and decanting: During this process, turbid water is allowed to settle for 2 to 24 hours. As with coagulation-flocculation, particles accumulate at the bottom of the basin. The clean water above is separated into another area for further treatment.
- Reverse osmosis filtration: Reverse osmosis uses semipermeable membranes to collect particles while clean water passes through. Contaminants are then drained from the filter and clean water is stored.
- Ultrafiltration systems: Similar to reverse osmosis, ultrafiltration involves filtering particles and suspended solids from turbid water.
In Conclusion
Turbidity is a critical measurement in wastewater treatment for assessing drinking water quality. Recognizing high turbidity levels can protect public health and reduce the risk of environmental impacts.
