Turbidity in Drinking Water: Understanding Regulations & Quality

Turbidity is a contaminant in finished drinking water and controlled by National Primary Drinking Water Regulations. These regulations are developed by the Environmental Protection Agency (EPA) and are legally enforced on public water systems to protect public health.

Purpose

• Turbidity measures the cloudiness of water and indicates the water quality. The more cloudy water is, the higher the turbidity level. High turbidity levels are linked with the presence of virus, parasites and bacteria that cause gastrointestinal illnesses.

Method

• Turbidity analysis is typically performed with a turbidity meter. A turbidity meter is an electronic device that shines light through a water sample and measures light absorbency. Microscopic organisms and clay or silt caused light to scatter and become absorbed. The more light absorbed, the higher the turbidity. Reference standards are needed to calibrate a turbidity meter.

Considerations

• The EPA regulates turbidity levels in finished drinking water. The federal regulatory limit of turbidity in drinking water from surface or ground sources is 5 nephelometric turbidity units (NTUs). Furthermore, water treatment systems that filter must have turbidity levels no higher than 1 NTU.