EPA Allows Use of LDO® Measurement of Dissolved Oxygen by Perry Brake

In a July 2009 memo to their Regional Administrators, EPA has allowed the use of Hach’s new luminescence dissolved oxygen (LDO) meter and probe for compliance monitoring of dissolved oxygen including use in the BOD/CBOD test. Some EPA regions have approved LDO use outright while others require a lab to apply for permission to use it.

The LDO system uses light emitting diodes to cause luminescence, the intensity of which is suppressed in the presence of dissolved oxygen according to DO concentration. With no moving probe parts, the LDO meter/probe is easy to use and maintain, and, because it requires no calibration or stirring, it is quick. There are no known interferences. With no membrane to replace, lifetime costs are minimized.

Hach’s tests and data gathered by users in the field have shown the LDO system to be as accurate or more so than membrane electrode instruments. LDO virtually eliminates DO measurement as a cause of excessive BOD blanks and, when coupled with use of Environmental Express plastic disposable BOD bottles which eliminate contamination problems, it would narrow probable causes of bad BOD blanks to source water quality, greatly simplifying troubleshooting for the BOD test.