In-Situ Inc. has announced that the United States Environmental Protection Agency (EPA) has granted nationwide approval to three In-Situ RDO optical dissolved oxygen methods under the Alternate Test Procedure (ATP) process. The In-Situ RDO methods are the only optical- or luminescence-based DO methods to pass the ATP approval process for measuring Biochemical Oxygen Demand (BOD), Carbonaceous Biochemical Oxygen Demand (CBOD) and Dissolved Oxygen (DO) under the Clean Water Act.

The ATP process validated three methods using the In-Situ RDO optical (luminescent) DO sensor as the determinative technique. Results from the validation establish the In-Situ RDO methods as the most widely tested and applicable optical DO methods available for compliance monitoring.

Ten federal- or state-certified laboratories performed testing in nine water and wastewater sample matrices. More than 1,300 samples were tested in municipal wastewater (influent and effluent), industrial wastewater from significant and categorical dischargers, ambient surface water, drinking water and other categories. No significant matrix interferences were observed in any of the 1,300 samples tested.

Entities holding National Pollution Discharge and Elimination System (NPDES) permits must use EPA-approved methodologies for BOD, CBOD and DO testing. The EPA Office of Science and Technology will recommend the In-Situ RDO methods for inclusion at 40 CFR Part 136.3. In the interim, NPDES permit holders can begin monitoring with the In-Situ RDO methods after seeking approval from their regional EPA authority.