Combined BOD and COD Analyzer

What is the Combined BOD and COD Analyzer?

A combined BOD and COD analyzer shares sample handling, digestion or incubation modules and data software for both parameters. It reports the two values together so that biodegradability can be assessed from a single workflow.

Overview

Combined systems pair a respirometric BOD module with a sealed-tube COD reactor and colorimeter, or integrate both into one instrument with shared calibration and reporting. The same sample is prepared once, split for the two determinations and documented in a common record, which reduces transcription errors and laboratory time. The ratio of BOD5 to COD, generally expressed as a percentage, indicates how biodegradable the wastewater is and guides the choice of treatment process, and tracking both values shows whether an effluent has changed character. Instruments may also calculate BOD from a short-term respirometric measurement and recent correlation, while retaining periodic five-day verification for regulatory reporting.

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?

• Respirometric BOD and sealed-tube COD in one system
• Shared sample preparation and data records
• Automatic BOD5 to COD ratio calculation
• Common calibration, QC and reporting software
• Separate incubation and digestion modules
• Export to LIMS with combined results

What are the technical specifications?

A typical combined bod and cod analyzer configuration offers parameters of BOD5, COD, ratio, BOD method of Respirometric, 6–12 bottles, COD method of Sealed tube, 150 °C, COD ranges of 0–150 to 0–15,000 mg/L, BOD ranges of 0–40 to 0–4000 mg/L and incubation temperature of 20 °C, ±0.5 °C. 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 Combined BOD and COD Analyzer is used in wastewater treatability and biodegradability assessment, industrial effluent characterisation, treatment plant performance monitoring and contract laboratory multi-parameter reporting. 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 Combined BOD and COD Analyzer?

Choose a combined system when both BOD and COD are reported routinely and the BOD to COD ratio is used to guide treatment or to characterise effluent. Confirm that the BOD and COD modules meet your respective methods and that the software can record both results against one sample.

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.