TURBIDITY TUBE

Turbidity is the opacity or muddiness caused by particles of extraneous matter, not clear or transparent. In general, the more material that is suspended in water, the greater is the water's turbidity and the lower its clarity. Suspended material can be particles of clay, silt, sand, algae, plankton, micro-organisms and other substances. Turbidity affects how far light can penetrate into the water. It is not related to water colour: tannin-rich waters that flow through peaty areas are highly coloured but are usually clear, with very low turbidity. Measures of turbidity are not measures of the concentration, type or size of particles present, though turbidity is often used as an indicator of the total amount of material suspended in the water (called total suspended solids). Turbidity can indicate the presence of sediment that has run off from construction, agricultural practices, logging or industrial discharges

The turbidity tube is a long thin clear plastic tube, sealed at one end with a white plastic disc with three black squiggly lines on it (seen when looking down the tube). The tube has a scale marked on the side.

Measures 10-400 NTUs. With increments of 10, 15, 20, 30, 40, 50, 60, 80, 100, 150, 200, 300, 400 NTUs.  

Procedure:

 

1. Holding the turbidity tube upright, and keeping it out of direct sunlight, look vertically down the tube and gradually pour the water sample into its column.

 

2. Stop pouring just before the black and white pattern at the bottom becomes invisible.

 

3. Now look to see where on the scale on the side of the turbidity tube the water level lies, and take this as your result in NTU.

 

4. To check your result, pour a small amount of the water sample out of the tube and repeat steps 2 and 3. Or get someone else to do it for you.