JTU

   abbreviation for Jackson turbidity unit, a unit formerly used in measuring water quality. The turbidity of water was measured by lighting a candle under a tall glass tube and filling the tube with the water sample until an observer looking down the tube could no longer see the candle flame through the water. The height of the water column determines the turbidity in Jackson turbidity units, using a table constructed for this purpose. Turbidity is usually measured now in a different unit, the NTU, using an instrument called a nephelometer.