By: Filtronics.inc
Water loses its transparency and takes on a hazy appearance when it contains a large quantity of suspended solid particles. While even a moderate lack of clarity is noticeable to even casual observers, the average person would probably describe a sample of such water as “cloudy” or “murky.” The technical term – turbidity – is not widely known to laymen outside the water treatment industry and the environmental science community, where it’s an important concept in defining and assessing water quality.
Excess turbidity in a water supply can have a number of causes. Materials that can become suspended in water include clay particles, silt, organic matter, plankton and other microscopic organisms. Some of the environmental conditions that cause turbidity in water include:
Erosion due to soil disturbances or lack of ground cover as a result of construction, mining, logging or wildfires.
Urban runoff of debris from developed areas, where the prevalence of paved surfaces does not allow natural settling of particles to take place from storm-water before it reaches creeks, streams and rivers.
Wastewater that has been cleaned but still carries some residual particles.
Decay of living organisms, both plant and animal.
Algae, especially when environmental conditions make bodies of water especially nutrient-rich and trigger algal blooms.
Bottom-feeding fish that stir up sediment as they seek out food.
The flow rate of a water body plays a big part in its potential for turbidity. The heavier a rain is, the greater its ability to pick up and carry sand, silt, clay and organic particles. Fast-moving water can carry more and larger particles because the force of the water overcomes the tendency of these particles to settle out of suspension. High velocity water can also stir up bottom sediments that then become re-suspended and increase turbidity even further.
Turbidity in itself may not necessarily present a health risk, but it can complicate the water disinfection process. Suspended matter can be a medium for the growth of microbes that do present a risk to human health. Turbidity is also sometimes associated with the presence of dangerous heavy metals such as lead, mercury and cadmium.
Precise measurements of water turbidity are made with a nephelometer, a device whose name is derived from the Greek word for “cloud.” Nephelometers measure the deflection of light that passes through a water sample; the greater the degree of light deflection, the greater the number and/or size of suspended particles in the sample. The resulting measurements are expressed in nephelometric turbidity units, or NTU.
In the U.S., the Environmental Protection Agency’s Surface Water Treatment Rule specifies that drinking water systems that make use of either surface water or ground water under the direct influence of surface water must not only disinfect their water but also filter it. In numeric terms, turbidity must never go above 5 NTUs, and turbidity must measure no higher than 1 NTU in at least 95% of daily water samples in any month.
Filtronics offers solutions for mitigating excess water turbidity including our EM-V System, a filtration system that uses alum to efficiently reduce turbidity by as much as 99 percent. For turbidity problems or any other water quality issues, consult the professionals at Filtronics. Call us at (714) 630-5040 for the most cost-effective solution to your specific filtration needs.
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