Respirometric BOD Analyzer

What is the Respirometric BOD Analyzer?

A respirometric BOD analyzer incubates samples in sealed bottles with carbon dioxide absorbers and records the pressure drop from oxygen uptake. It gives continuous BOD data without dilution oxygen measurement or titration.

Overview

Each bottle holds a magnetic stirrer and a seal with a pressure sensor, and the headspace carbon dioxide produced by microbial respiration is absorbed by potassium hydroxide, so the pressure change reflects oxygen consumption alone. The controller reads each bottle in sequence, converts the pressure difference into milligrams of oxygen per litre using the bottle volume and sample volume, and displays a BOD curve updated every few hours. Instruments typically handle six to twelve bottles at once, maintain 20 °C in an incubator or water bath, and allow individual start times so that samples can be added during the day. Selection of sample volume determines the measuring range, from 0 to 40 mg/L for undiluted sludge-free samples up to 0 to 4000 mg/L with small sample volumes and the appropriate inoculum.

How does it work?

BOD is determined by allowing microorganisms to oxidise biodegradable matter under controlled conditions and measuring the oxygen they consume. In the dilution method, sample is diluted with seeded, oxygen-saturated water, filled into bottles and incubated at 20 °C, and dissolved oxygen is measured before and after five days; the difference, corrected for the seed blank and dilution factor, gives BOD5. In respirometric systems, the sample is incubated in a sealed bottle with a carbon dioxide absorber, and the pressure drop caused by oxygen consumption is measured and converted continuously into oxygen uptake. Combining manometric BOD measurement with nitrification inhibition focuses the result on carbonaceous demand. Results are reported in milligrams of oxygen per litre, and the ratio of BOD to COD indicates how readily the wastewater can be treated biologically.

What are the key features?

• Pressure sensing with carbon dioxide absorption
• Six to twelve bottles with individual start times
• Continuous BOD curve updated automatically
• Selectable sample volume for different ranges
• 20 °C incubation with stirring
• Data export and curve comparison software

What are the technical specifications?

A typical respirometric bod analyzer configuration offers measurement principle of Respirometric pressure measurement, bottle capacity of 6–12 bottles, measuring ranges of 0–40 up to 0–4000 mg/L by sample volume, incubation temperature of 20 °C, ±0.5 °C, test duration of 5, 7 or 10 days selectable and stirring of Magnetic, continuous. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Respirometric BOD Analyzer is used in municipal wastewater plant routine control, industrial effluent biodegradability testing, river and lake organic load monitoring and laboratory BOD5 determination without titration. Across the wider BOD Analyzers class, laboratories also deploy it for municipal wastewater treatment plant control, industrial effluent biodegradability assessment and discharge permit compliance monitoring.

Which standards and certifications apply?

Relevant standards and methods include ISO 5815-1, ISO 5815-2, Standard Methods 5210 B, EPA 405.1 and ISO/IEC 17025. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

BOD measurement is sensitive to the seed, the dilution water and the incubation conditions, so dilution water must be free of chlorine and organic matter and should be aerated and seeded consistently. Nitrification inhibitors are added when only carbonaceous demand is required, since nitrifying bacteria consume oxygen and inflate results. Dilution must bring the final dissolved oxygen into the accepted window, typically at least 2 mg/L remaining and a depletion of at least 2 mg/L. Bottles, stoppers and seals must be clean and leak-free, especially in respirometric systems where a small leak ruins the pressure measurement. Incubation must be maintained at 20 ± 1 °C, and reference standards such as glucose-glutamic acid check the whole procedure.

How do I select the right Respirometric BOD Analyzer?

Choose a respirometric system when routine BOD5 testing is required and you want automatic readout without titration. Confirm that the range covers your samples and that the incubator holds 20 °C accurately, and plan seeding and nitrification inhibition as required by your method.

How does it compare with other BOD Analyzers variants?

Select the method from the data you need and the resources available. Respirometric systems automate incubation and readout, remove the need for titration and allow several bottles to run in parallel with continuous data, which suits routine plant control. Dilution methods with dissolved-oxygen measurement remain the reference approach for regulatory reporting and are used for samples with high or variable BOD. No measurement is valid without correct seeding, dilution and nitrification control, and the seed blank must be run with every batch. Choose a combined BOD and COD system if both parameters are reported routinely, since sharing incubation and reagents simplifies workflow. For continuous control, online respirometric instruments provide trend data but must be correlated with laboratory results.