Reaction mass of 3-Isocyanatolmethyl-3,5,5-trimethylcyclohexyl isocyanate (Isophorone diisocyanate) with 4-Methylpentan-2-one oxime.

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

Deviations:

no

GLP compliance:

no

Remarks:

According to ISO/IEC 17025

Test material

Test material information

Test material form:

liquid

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Activated sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant, not adapted, not pre-conditioned; 0.2 g/l dry matter in the final mixture

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

250 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The activated sludge was used after sampling from the treatment plant without adaptation. However, the sludge was pre-conditioned for 1-4 days (aerated but not fed). Prior to the test the sludge was washed twice with tap water. The test material was diluted with mineral salts medium to give a final DOC concentration of about 50 mg/l. The activated sludge was applied to give a dry substance content of 0.2 g/l.
The dry substance content of the activated sludge is gravimetrically determined in regular intervals after drying of the sludge at 105°C.
For each test series the following number of test flasks was set up:
Test suspension (T) 2 replicates: containing activated sludge + test medium + test substance
Inoculum blank (B), 2 replicates: containing activated sludge + test medium
Procedure control (R), 2 replicates : containing activated sludge + test medium+ diethyleneglycol as ready biodegradable reference compound
The test vessels were stirred (100 r.p.m.) and aerated with synthetic CO2-free air for a maximum test period of 28 days. The air leaving the individual vessels was passed through gas-absorption bottles filled with NaOH. The pH-value was checked at the beginning and was adjusted to pH 7.4 +/- 0.2 with HCl. At the end of the test the pH was recorded.
The elimination of the test material was followed by DOC determinations at regular intervals. First samples were analyzed before the addition of the sludge and 3 h after starting the test. The trapped CO2 in the gas-absorption bottles was determined as inorganic carbon (IC).

Reference substance

Reference substance:

diethylene glycol

Results and discussion

% Degradation

Parameter:

% degradation (DOC removal)

Value:

71

Sampling time:

28 d

Remarks on result:

other: elimination due to adsorption by the activated sludge or other physico-chemical processes.

Details on results:

No biodegradation of the substance based on CO2 evolution was observed.

BOD5 / COD results

Results with reference substance:

99% biodegradation after 14d.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not inherently biodegradable

Conclusions:

Due to the limited water solubility almost complete elimination in wastewater treatment can be expected.

Executive summary:

The biodegradability of SPRPUZP exposed to activated sludge of a municipal sewage treatment plant was investigated under aerobic static conditions.
Based on the data of the individual DOC determinations SPRPUZP reached a biodegradation of 71% after 28 days. Due to the limited water solubility the DOC elimination was calculated with respect to the theoretically applied TOC concentration.
Due to the limited water solubility of Da-08129/19 the highest elimination was already attained after 1 day.
The positive control, diethyleneglycol, showed 99% biodegradation after 14 days of incubation thus confirming suitability of inoculum and test conditions. The test was considered valid, since the degradation of the reference compound reached more than 70% within 14 days of incubation.
No biodegradation of SPRPUZP based on CO2 evolution and calculated as % ThCO2 was observed. The extent of mineralization of the procedure control with diethyleneglycol was within the same range showing a value of 79% based on ThCO2.
Based on the mineralization data SPRPUZP is not inherently biodegradable under the conditions of the OECD guideline no. 302, since less than 20% degradation was attained after 28 days of contact time. However, due to the limited water solubility almost complete elimination in wastewater treatment can be expected.