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For industrial and testing laboratories, the regulatory requirement adds another layer: biodegradability tests according to OECD 301 F, DIN EN 29 408 and ISO 9408 must be carried out in a standard-compliant manner. Errors in sampling, dilution or inhibitor use jeopardize not only the results but also the legal certainty of the entire investigation.

Where the biggest stumbling blocks lie

Oxygen-saturated water contains only about 9 mg/L of dissolved oxygen at 20 °C. For a sample with 5,000 mg/L BOD it is immediately apparent that this oxygen content is far from sufficient - without dilution, nothing works here. Defined dilution series extend the measurement range up to 400,000 mg/L, but selecting the right dilution step requires experience.

Inhibitory or toxic substances are another classic interference factor: they can slow down or completely halt biological degradation, so the measured BOD value falls below the actual load. Biodegradability tests according to OECD, DIN and ISO therefore require a targeted check for inhibitory effects.

Temperature, sample homogenization and correct inoculation also determine the significance of the results. Anyone who does not control these influencing factors systematically often searches for a long time in everyday laboratory work for the cause of implausible values.

Compact practical knowledge for industrial and testing laboratories

The new BOD handbook from WTW® provides orientation across the entire application range of respirometric measurement - from routine BOD determination to biodegradability tests according to OECD and AT4 determination. Across more than 60 pages, the fundamentals of measurement technology are covered alongside concrete tips for practice.

Topics covered include:

• Fundamentals of BOD measurement and respirometry

• Ready biodegradability according to OECD, DIN and ISO

• Industrial wastewater: sampling and interference factors

• Handling inhibitory and toxic substances

• Measurement range extension via dilution series (up to 400,000 mg/L)

• AT4 determination for waste and soil samples

• Evaluation of BOD curves and error detection

• Cleaning, maintenance and quality assurance

Numerous practical examples, quick-reference guides and tips for avoiding errors enable direct implementation in the laboratory. The handbook is aimed at specialists in industrial and testing laboratories, engineering offices and anyone who engages more intensively with biodegradability testing and respirometric measurement technology.

→ Download BOD handbook now