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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Potassium hydrogen oxalte can be asimilated to oxalic acid: in water solution oxalte anion is present as occurs with the oxalic acid. 
A series of degradation studies was carried out in line with traditional BOD tests. These tests follow the mineralisation of oxalix acid in time (mostly in 5 days) and compare the oxygen consumption (BOD) with the Chemical Oxygen Demand (COD). Test conditions were generally in line with the strict conditions described for the screening tests for ready biodegradability (low inoculum, low test substance concentration, unadapted sludge, OECD 301). The results show that oxalic acid is readily biodegradable under aerobic conditions. This was also the case in seawater. The main part of the process seems to occur within the "10-day time window".
In a anaerobic test acc. to ISO 11734, oxalic acid was also rapidly degraded.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

A range of BOD tests is available all showing that oxalic acid is degraded rapidly in 5 days. The key study in itself is sufficient, but supporting studies confirm the findings. It is concluded that oxalic acid is to be considered as readily biodegradable. The degradation process seems to start without a delay and thus also the requirement on the rate of degradation (the 10 -day window) is met.

 Reference  Test type  % degradation  Reliability
 1968 Young KEY STUDY:Similar to EU Method C5: BOD test in large volume. measured oxygen consumption, TOC removal, bacterial growth after 5 days: 89%after 20 days: 89%   2
 1985 Deshkar  BOD5 test at 20, 25 and 35 degree C after 5 days: 54, 92 and 95 %    2
 1958 Gaffney  BOD test, standard dilution method  after 5 days: 78 -94%  2
 2004 Hongwei  ISO 11734, anaerobic degradation  rapidly biodegradable under anaerobic conditions  2
 1981 Takemoto  BOD5 test, standard dilution method, also in seawater  after 5 days 68%; in seawater 64%  2