Automatic Diluting BOD Analyzer

What is the Automatic Diluting BOD Analyzer?

An automatic diluting BOD analyzer prepares seeded dilutions and fills incubation bottles reproducibly before the five-day test. It removes the main source of manual error in the dilution method and improves comparability between operators.

Overview

The instrument dispenses dilution water and sample in programmed ratios into a series of bottles, adds seed and nitrification inhibitor, aerates the dilution water and mixes the contents to dissolve oxygen evenly. Barcodes or position records link each bottle to its dilution, so the operator does not need to label and track bottles manually. After five days of incubation in a separate 20 °C cabinet or bath, dissolved oxygen is measured, often with an optical sensor that avoids membrane maintenance, and the software calculates BOD5 for each valid dilution and flags those outside the acceptance window. Because dilution and seeding are the largest sources of variability in the method, automation improves laboratory reproducibility, although the incubation step itself still requires a stable cabinet.

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?

• Programmed sample and dilution water dispensing
• Automatic seed and inhibitor addition
• Barcode or position tracking of dilutions
• Optical dissolved oxygen measurement option
• Automatic BOD5 calculation per valid dilution
• Flags bottles outside the acceptance window

What are the technical specifications?

A typical automatic diluting bod analyzer configuration offers dilution ratios of Programmable, typically 1:5 to 1:500, bottle capacity of Up to 20 per batch, volume accuracy of ±1 percent, seed dosing of Automatic, 0.1–5 mL, dissolved oxygen measurement of Optical or membrane sensor and incubation temperature of 20 °C, ±0.5 °C in separate cabinet. 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 Automatic Diluting BOD Analyzer is used in regulatory BOD5 reporting laboratories, municipal and industrial effluent testing, high-volume contract laboratories and samples with high or variable BOD requiring multiple dilutions. 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 Automatic Diluting BOD Analyzer?

Choose an automatic diluting system when BOD5 is reported routinely and dilution error or operator workload is a problem. Confirm that the acceptance-window logic follows your method and that the incubation cabinet holds 20 °C reliably, since the dilution step is automated but incubation is not.

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.