BOD Testing: Biochemical Oxygen Demand

The biochemical oxygen demand (BOD) test most closely models aerobic waste treatment and the aquatic ecosystem. It measures oxygen taken up during the oxidation of organic matter. The test most often runs for a five-day period, but can run 7 or 10 days as well, depending on specific sample circumstances.

BOD testing has its widest application in measuring waste loadings of treatment plants, and in evaluating the efficiency of treatment processes. It is of limited use in industrial wastewaters containing heavy metal ions, cyanides, and other substances toxic to microorganisms.

COD Testing

Comprehensive Hach COD systems offer many advantages, including premeasured, ready-to-use reagents; vial chemistries with unique sealing properties and reduced reagent usage; and our space-saving COD Reactor for sample digestion. Results are read directly using a spectrophotometer or colorimeter. The new Manganese III COD Method and the USEPA-approved Dichromate COD Method share many of the same benefits, such as accurate results and labor-saving procedures. Plus, when you purchase a COD system from Hach, a lifetime of technical support is included.

With prepared COD reagents you save time — no weighing, preparing, pipetting and transferring chemicals. You'll no longer have to purchase or dispose of the large amounts of silver and mercury compounds required in the macro COD method. And prepared reagents significantly minimize metals waste.

With the new Manganese III COD Method, you can prepare up to 25 samples in approximately 30 minutes and digest them in one hour. From start to finish, results are available in less than 90 minutes. With the USEPA-approved COD Method, prepare 25 samples in minutes and digest them in two hours. Because you can complete COD tests easily, quickly, and accurately, informed decisions can be made promptly regarding process control adjustments.

Instead of a macro reflux method, Hach COD methods use a closed reaction system, which accurately reflects the real environmental effects of the sample. Unique reagent vials prevent escape of volatile organics, assure complete digestion, and eliminate the use of condensers. The small reagent volumes used in Hach's micro COD systems not only reduce the danger of spills, but also minimize reagent usage. The reagent vials require no flame sealing, saving time and reducing equipment handling. Test range is 0-40 mg/L as C (ultra-low range), 0-150 mg/L as C (low range) 0-1500 mg/L as C (high range), 0-15000 mg/L as C (ultra high range). Method detection limit is between 2-5 mg/L COD.


The TOC method from Hach provides a reliable and practical means for water treatment facilities to frequently measure organic carbon for optimization of their treatment process. Instead of purchasing an expensive, traditional TOC analyzer or outsourcing TOC determinations to a contract laboratory, Hach’s method provides TOC results accurately and inexpensively right at your facility.

Hach’s TOC method is a unique and simplified test developed for the measurement of organic carbon in a variety of sample matrices. The method involves the oxidation of sample carbon to carbon dioxide by persulfate digestion. The carbon dioxide diffuses into a colored pH indicator solution, where it is converted to carbonic acid. The resulting color change is directly proportional to the concentration of carbon present in the sample. Test range is 0-20 mg/L as C (low range) with a 0.2 mg/ detection limit, and  20-700 mg/L as C (high-range) with a 20 mg/L detection limit.

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