Turbidity testing is an important water quality parameter, however it only tells half the water quality story.

Turbidity testing measures scattered visible light which results from various types of matter in the water, mostly providing an indication of the amount of larger particles. UV 254nm measures the amount of UV light absorbed or transmitted through the water, providing an indication of the amount of natural organic matter (NOM) in the water.

Although turbidity is not an organic test parameter, since it has long been used as a measure of general water quality it is commonly being used instead of performing an actual measure of organic content. This could also be due to the fact that until the more recent use of the UV 254nm organic test parameter, organic testing has not been easily attainable given the expense, time and complexity of measuring the organic test parameters in the past. Therefore turbidity testing used to be the only real option.

This reliance upon turbidity tests alone without analysis of organics can result in the ineffective optimization of a wide range of treatment methods. Problems that occur include inadequate chemical dosing of coagulants and disinfectants, poor filter performance optimization, increased DBP formation and more.

Further understanding of the water quality from simply performing UV 254nm organic testing can greatly improve these treatment processes and their finished drinking water or wastewater quality.

Another water quality parameter that is sometimes used as a surrogate to measuring organics is color. Since humic acids can sometimes give a visible color to the water, the visible light used to test color can give an indication of some organics. However, color is a far inferior method to performing a UV 254nm test and generally it is not recognized as an accurate organic test parameter.