Turbidity in Stormwater FAQs
Turbidity describes the amount of optical diffraction (the bending of light as it passes around an object) caused by particulates suspended in water. Measuring turbidity indirectly measures the number of particulates in the water.[vii] The particulates measured by turbidity can be either solid or liquid (i.e. oil droplets),[viii] however, the solid particulates are predominantly used in turbidity measurements. Turbidity is often used as a surrogate measurement for total suspended solids although no correlation between turbidity and TSS measurements can be made.[ix]
Stormwater runoff can create turbid conditions in water when it picks up particulate debris from hard surfaces and transports it to water bodies. Turbidity in stormwater runoff is usually made up of rock and soil fragments, dirt and debris from roads and vehicles. [vii] TSS, a related pollutant, measures the mass of particulates of varied origin suspended in a moving body of water, with no direct relationship between turbidity and TSS measures. The particles causing turbidity are insoluble in water and will settle out of suspension with enough time.[viii]
Turbidity should be removed from stormwater because its presence in drinking water sources has negative effects on humans and the environment.
The effects of high turbidity levels in water ingested by humans often mean higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria, which can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.[i]
Turbidity can also make streams less aesthetically enjoyable and can have negative impacts on plants and wildlife. Turbidity reduces visibility and absorbs light, which can increase stream temperatures and reduce photosynthesis.[ii] Resulting negative impacts of turbidity on plant and wildlife include:
- interference with aquatic plant photosynthesis, reducing the amount of food, habitat and dissolved oxygen available for other species;[iii]
- fine particles clogging and abrading fish and insect gills and tissue and interference with egg and larval development;[iv] and
- pollutants such as pesticides and PCBs adhering to the surfaces of particulates and being transported through stormwater into aquatic environments.[v]
Turbidity can be removed from industrial stormwater through a physical process of separation, absorption and enhanced media filtration typically found in a passive media filter. Our Aquip passive media filter offers an enhanced level of stormwater treatment for turbidity. Aquip can operate in-line after a gravity separator and before a polishing system. Find out more about the Aquip passive media filter.