What is Turbidity? Turbidity is described as "an expression of the optical property that causes light to be scattered and absorbed rather than transmitted in straight lines through the sample" (Standard Methods, 1995). As light passes through pure water, it travels along a relatively undisturbed path. The light passed through fluids, with suspended particles present, is greatly distorted by absorption or scattering, caused by these particles. Nephelometry, International Standard Method (ISO 7027), is a method for detecting this scattered light and has been approved by the Environmental Protection Agency (EPA), for testing water quality in producing products destined for human consumption, manufacturing operations, and surface/waste water.
Why Measure Turbidity? All bodies of water have a turbidity component that can be measured. Flux rates of particles between bodies of water or sediment deposition rates can be determined from turbidity measurements. Turbidity can also be measured as a parameter to simply characterize a body of water. For example, systems with higher turbidities will absorb sunlight warming the water or scatter light causing a decrease in photosynthetic activity in algae. Turbidity also provides a substrate and interferes with treatment of water, therefore promoting microbial growth, allowing for the presence of disease causing organisms such as bacteria, viruses, and parasites that can cause nausea, cramps, diarrhea, and associated headaches. Water and wastewater industry monitors turbidity in drinking water treatment plants to make sure incoming raw water will not inhibit the chlorination process that helps disinfect and purify municipal drinking water.