Glutaral

Biodegradation in water and sediment: simulation tests

Description of key information

Glutaraldehyde is biodegradable in activated sludge, sediment and pond water under aerobic as well as anaerobic conditions: Glutaraldehyde dissipated in the aerobic water/sediment system with the half-life of 1.25 d (12 °C). The corresponding rate constant is 0.555 d-1.

Additional information

The biodegradability of glutaraldehyde 50% was tested according to the OECD Guideline 303 A (1993) respectively ISO Standard 11733 in the Activated Sludge Simulation Test (BASF AG 97/0329/30/1). The test duration was 73 days, the DOC concentration of the test substance in the influent was 20 mg/l; the nutrient solution was 53 mg/L DOC in the influent, the dry weight of the added inoculum (domestic sludge) was 2.5 g/l, the mean retention time was 6 hours. Samples were taken from the influent and effluent of the two parallel running units; one unit served for control whereas the second one served as test unit. The adaptation phase was < 1 day, followed by a plateau phase of 72 days. The mean biodegradation was 97 % after 73 days with a corresponding standard deviation of 1% (95% confidence interval).

The aim of four other studies was to investigate the environmental fate of glutaraldehyde in pond water and sediment under aerobic (EPA Subdivision N Pesticide Guideline 162-4; PTRL West 365W-1 and ABC Lab 32736) and anaerobic conditions (EPA Subdivision N Pesticide Guideline 162 -3; PTRL West 365W-1 and ABC Laboratories 32735). However, the studies conducted at ABC Laboratories are considered as supporting information since they are old and do not fulfil the current requirements of the OECD 308. There are several deficiencies:

- only one combination of sediment + water tested (two required)

- source of water and sediment not given

- repeatability and sensitivity of analytical methods have not been reported

- nothing is said about an acclimation period

- transformation products have not been identified

- transformation rate in the sediment was not determined

- mineralization rate was not determined, neither the transformation rate for the whole system

- Anaerobic study only: - no evidence has been provided about anoxic conditions, e.g. oxygen contents have not been reported.

 

However, the supporting studies confirm the results of the key studies with respect to rapid aerobic and anaerobic degradation of glutaraldehyde in aqueous systems.

 

The results of the key-studies can be summarized as follows:

Aerobic conditions: In the beginning of the study (Esser, 1994)glutaraldehyde was found mainly in the river water (86.9-90.8% of the dose within the first 12 hours). Glutaraldehyde decreased rapidly in the water and was completely metabolized within 48 hours. The major metabolite was ¹⁴CO₂(total of 80% in the headspace and the water at the end of the study). Glutaric acid was formed as an intermediate in the water phase (18.9-21.5% of the dose at 12 hours), but was itself completely metabolized within 48 hours. Radioactivity from glutaraldehyde or its metabolites was incorporated into biomass or adsorbed to the sediment (maximum of 21-25.3% at 48 hours) and could not be extracted completely. The calculated pseudo-first order half-life of glutaraldehyde in water under aerobic conditions was 10.6 hours at 25°C corresponding to 1.25 d at 12°C.

 

Anaerobic conditions: Glutaraldehyde and its metabolites were predominantly associated in the aqueous phase (Esser, 1994). After 123 days, >87% of the radioactivity was still in the aqueous phase, and sediment levels were 7.6-9.2%. The overall material balance of radioactivity was 98.7 +/- 2.5%. The parent compound was rapidly metabolized with the first-order half-life being 7.7 hours. Glutaraldehyde was transformed to 5-hydroxypentanal which accounted ca. 37% of applied radioactivity on day 1, after that it declined below 10% and after 30 days it was not detected at all. Glutaraldehyde was transformed to Compound A via Aldol condensation, cyclization and dehydration. Compound A accounted about 10-20% of total radioactivity from day 1 on. The second stable transformation product was 1,5-pentanediol which accounted 35% of radioactivity on day 1, peaked on day 3 to 76% after two weeks and accounted 70% of radioactivity at the end of the test. Less than 10% of radioactivity was detected in the sediment. Insignificant amounts of CO2 were produced during the experiment.The calculated pseudo-first order half-life of glutaraldehyde in water under anaerobic conditions was 7.7 hours.

In conclusion, the results of the different studies confirmed the results of the ready biodegradability test; therefore, the test substance can be regarded as biodegradable in the activated sludge as well as the pond water and sediment simulation test.