While many water professionals worry about getting chlorine into water and establishing a chlorine residual, other water professionals worry about removing chlorine from water.

  • Example 1: Before water from a well can pass a coliform bacteria test at a certified laboratory and get approved for human consumption it must test as having absolutely no chlorine residual in it.
  • Example 2: Federal, State and Local Environmental Laws/Regulations prohibit the discharging of highly chlorinated water from a wastewater treatment facility or from any other water processing facility. Chlorine, even in low concentrations, poses a serious danger to the ecosystem and the releasing of too large an amount into environment can wipe out the area’s vegetation and animal life very rapidly.

What Type of Chlorine Should One Test For?

Typically speaking, when concerned about the amount of chlorine residual in the discharge from any sort of wastewater treatment facility, most people check for total chlorine. Testing solely for free chlorine would not suffice for environmental purposes because combined chlorine, also called chloramines, can still have harmful effects on the environment despite not having the as great an oxidation potential as free chlorine.

How Can One Test for Low Levels of Total Chlorine?

Test Strips: Quick, easy and cost effective. Test strip methods for chlorine concentration determination offer extreme amounts of convenience and require little or no technical training. Just dip the strip and compare the color of the test area to a color chart. (total chlorine, ultra low total chlorine)

DPD: Typically used in conjunction with a colorimeter, DPD methods for chlorine concentration determination give more precise results than most visual methods, but as stated, they typically require the use of instrumentation (see eXact Micro 7+). For environmental compliance monitoring and reporting purposes, most government bodies require the use of an EPA Compliant DPD testing method.

Titrations: A time consuming method which typically uses DPD in liquid form and requires a certain amount of laboratory skills. Not very practical for field work. Uses liquid reagents which have a shorter shelf-life than comparable powders, tablets, etc.

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