We do not know of an International Standard for free chlorine levels in irrigation water but we do know that most States in the US require wastewater treatment plants to neutralize TOTAL chlorine levels before discharging water into the environment and that wastewater treatment facilities must test for total chlorine residuals in their effluent streams on a regular basis to make sure the chlorine concentrations stay virtually non-existent.

Why worry about chlorine in the environment?

If allowed to enter the environment chlorine can and will effectively kill or damage biological organisms that it comes in contact with. In great enough concentrations chlorine will wipe out all plant life in a body of water as well as any animals or fish in the water.

We use chlorine to render safe (i.e. KILL) biological contaminants in our drinking water and if released into a natural habitat the chlorine will render safe (i.e. KILL) any and all plant an animal life until it loses its effectiveness.

Testing for free & total chlorine?

Whether you prefer test strips, wet chemistry kits or a water testing meter… you have plenty of choices when it comes to testing for both free and total chlorine levels in drinking and treated waste 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.