AWWA ACE59859

Particle count and on-line turbidity measurements are affected by bubble formation, and the water industry does not routinely employ methodology that will determine when bubbles cause spurious measurements. Bubbles were measured as particle counts in laboratory experiments and at a full-scale utility, and particle counts decreased when the pressure in the measurement cell was increased during sampling. For example, if a water was supersaturated with dissolved gas, particle counts were nearly 3 orders of magnitude higher when the sample was not pressurized, compared to the same measurement made at an applied pressure of 15 psi. Failure to account for these spurious signals can cause water treatment operators and researchers to draw faulty conclusions about efficiency of water treatment in removing particles. In laboratory experiments, spurious turbidity spikes, increasing turbidity, and gas accumulation in the measurement cell occurred in on-line turbidimeters. Includes 29 references, table, figures.