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In-Situ, Inc. RDO Sensor Recieves EPA Approval for NPDES Permit Holders for DO, BOD, and CBOD

On May 18, 2012, three In-Situ RDO methods received nationwide U.S. Environmental Protection Agency (EPA) approval for optical dissolved oxygen measurement.  The In-Situ RDO methods are included in the final Methods Update Rule (http://water.epa.gov/scitech/methods/cwa/update_index.cfm).  National Pollution Discharge and Elimination System (NPDES) permit holders may begin monitoring with In-Situ RDO methods.  These optical (luminescent) methods can be used in the measurement of Biochemical Oxygen Demand (BOD), Carbonaceous Biochemical Oxygen Demand (CBOD), and Dissolved Oxygen (DO) under the Clean Water Act.  This is the first optical DO method to receive nationwide, Tier 3 EPA approval for CBOD, along with BOD and DO.  The three EPA approved methods are:


  • In-Situ Inc. Method 1003-8-2009 Biochemical Oxygen Demand (BOD) Measurement by Optical Probe (ATP Case No. N09-0020)
  • In-Situ Inc. Method 1004-8-2009 Carbonaceous Biochemical Oxygen Demand (CBOD) Measurement by Optical Probe (ATP Case No. N09-0021)
  • In-Situ Inc. Method 1002-8-2009 Dissolved Oxygen Measurement by Optical Probe (ATP Case No. N05-0014)


RDO technology offers the latest in optical-based measurement of BOD, CBOD, and DO. Advantages include:


  • Greater accuracy and reliability than membrane based methods
  • Greater peace of mind—RDO methods are EPA approved for BOD, CBOD, and DO determination
  • Option to use either stirred or non-stirred techniques for BOD, CBOD, and DO determinations
  • No hydration effects – even if the sensor dries out
  • Simple calibration procedures and a sensor cap loaded with calibration coefficients
  • Stable, long-lasting calibration
  • Excellent response time and stability in samples that range from surface water, to treated wastewater, to industrial sewer discharge
  • Resists fouling by oils and fats
  • Unaffected by interferences—Sulfides, sulfate, carbon dioxide, ammonia, pH, chloride, or chlorine
  • Significantly less maintenance lowers overall costs


The In-Situ, Inc. RDO sensor is available as a standalone sensor called the RDO Pro, or on multiparameter water quality instruments like the TROLL 9500 and AquaTROLL 400.



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