Turbidity – Clarifying Low Level Measurements
by James W. Egan, Jr, PhD.
In the past 10 years, the analysis of turbidity has become far more than just a measure of water clarity. Now, low level turbidity analysis is becoming the method of choice for protection against emerging pathogens such as Cryptosporidium and Giardia. By assuring proper water filtration, risks from a variety of undesirable contaminants in our nation’s water supplies can be reduced.
In 2002, the EPA published the LT1ESWTR (Long Term 1 Enhanced Surface Water Treatment Rule) mandating turbidities in combined filter effluent to read at or below 0.3 NTU. The EPA hoped this action would achieve a 2 log (99%) removal of Cryptosporidium1. There is presently consideration to lower this to 0.1 NTU. To achieve the EPA’s goals, constant turbidity monitoring of filtered water is critical. This monit
pH is one of the most common analyses in soil and water testing. An indication of the sample’s acidity, pH is actually a measurement of the activity of hydrogen ions in the sample.
pH measurements are reported on a scale from 0 to 14, with 7.0 considered neutral. Those solutions with a pH below 7.0 are considered acids, and those between 7.0 and 14.0 are designated bases. The pH scale is logarithmic, so a one unit change in pH actually reflects a ten fold change in the acidity. For instance, orange juice, pH 4, is ten times more acidic than cottage cheese, which has a pH of 5.
Low pH waters have a tendency to cause corrosion, while high pH waters may contribute to scale formation in, for example, boiler or cooling systems.
Small changes in pH, 0.3 units or less, are usually associated with relatively large changes in other water qualities — t
Measuring Water Hardness
Hard water is water that has high mineral content (as opposed to "soft water"). Calcium is the most common mineral associated with water hardness. While hardness is not generally a health hazard it can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment. In domestic settings, hard water is often indicated by a lack of suds formation when soap is agitated in water, and by the formation of limescale in kettles and water heaters. Wherever water hardness is a concern, water softening is commonly used to reduce hard water's adverse effects.
Calcium hardness in pools and spas can often present problems for the
Measurement of chlorine in the field is relatively easy. The fact that chlorine can be easily detected and measured makes chlorine a favorite water sanitizer for those concerned with the safety of water supplies, public and private pools, and other sources or reservoirs. Chlorine concentrations in the range of 0.1 to 0.4 parts per million are usually maintained in municipal supplies, while ranges from 1 to 3 ppm are used in both pools and spas.
Three types of chlorine can be measured:
- Free chlorine – most effective as a disinfectant
- Combined chlorine – formed when free chlorine reacts with other compounds within the water.
- Total chlorine – the sum of free and combined chlorine.
Since free chlorine is the primary disinfectant, a means of measuring free chlorine is ne