Propane-1,3-diyl bis(4-aminobenzoate)

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

yes

Specific details on test material used for the study:

Test item: PU-2017-775
Chemical names: Trimethylene glycol bis 4-aminobenzoate
1,3-Propanediol bis(4-aminobenzoate)
Molecular formula: C17H18N2O4
CAS number: 57609-64-0
Purity: 99.8% (CoA)
Lot number: 1658304
Carbon content: 64.96% (calculated by Hydrotox on the basis of the molecular formula)
Water solubility: Insoluble

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Remarks:

Activated sludge from the municipal wastewater treatment plant AZV Breisgauer Bucht was used as inoculum with a concentration corresponding to 30 mg dry solids per litre.

Details on inoculum:

Activated sludge from the municipal wastewater treatment plant AZV Breisgauer Bucht was used as inoculum with a concentration corresponding to 30 mg dry solids per litre. The treatment plant clarifies predominantly domestic wastewater and has a capacity of 600,000 inhabitant equivalents. Sampling date of activated sludge was on 13 March 2018. The dry solid content of the activated sludge was 4.4 g/L. It was determined by weight measurements after drying at 105 °C for 5 hours (mean of triplicate measurements). The activated sludge was washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge.

Duration of test (contact time):

42 d

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

In total three reactors containing the test item, three reactors containing only inoculum (blank), three reactors containing the reference compound and one reactor containing test item and reference compound (toxicity control) were set up.
10.2 mL activated sludge was filled up to 1500 mL with 1489.8 mL mineral medium corresponding to 30 mg/L dry solids. The system was sealed and aerated with CO2-free air overnight. The reactors were kept mixed with magnetic stirrers. On the next day, the absorber wash bottles were filled with 0.2 M NaOH and the test substance was added into the two test vessels, into the toxicity control vessel and the abiotic control vessel. The reference compound was added into the reference vessels and into the toxicity control vessel and the toxicant into the abiotic control vessel. The aeration rate was kept at a rate of 30 - 100 mL / min (1.6 - 5.5 bubbles / second) and determined visually daily on working days. The determination by counting the gas bubbles over a defined period using a stopwatch was made on days 11 and 29. The CO2-free air production system, the air-tightness of the whole experimental set-up, the aeration of the absorber flasks and the magnetic stirrers were controlled daily on working days.
At the beginning of the study the IC concentration of the 0.2 M NaOH used for the CO2-absorption flasks was determined as 3.46 mg/L. The IC in the reactors at the beginning of the test was 0.78 mg/L. On the 4th, 7th, 11th, 14th, 22nd, 28th, 35th and 42nd day, 6 mL NaOH from the first of two CO2-absorber flasks connected in line was sampled and the IC's were determined. The vials were immediately closed with sealing film in order to avoid CO2 uptake from the air. On the 43rd day 2 mL of 4M hydrochloric acid (HCl) was added into each reactor to release the CO2 dissolved in water. On day 36 the IC was determined in both CO2-absorber flasks in line.
IC measurement was performed with a total carbon analyser (TOC-L Shimadzu) by purging the inorganic carbon with H3PO4 (25%) using a non-dispersive infrared (NDIR) detector.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

74.3

Sampling time:

42 d

Details on results:

Results:
• The degradation of the test item at the end of the test was 74.3% (d 42 after acidification, mean of three replicates).
• In two replicates a degradation of >60% was reached within 28 days and within a 10-d window. Therefore, in two of three replicates, the criteria for ready biodegradability were reached (60% of ThCO2 within a 10-d window).
• In one replicate a degradation of >60% was also reached within a 10-d window, however not within 28 days. This may be explained with the insolubility of the test item and a prolonged lag-phase. Therefore, in this replicate the criteria for ready biodegradability were not reached, but the criterion for non-persistence (60% of ThCO2 within 60 days).
• The degradation of the toxicity control after 14 days was 51.2%. The test item had no inhibitory effect on the inoculum according to the criterion of the guideline.
• In the toxicity control, the test item was also degraded by more than 60% within 28 days and within a 10-d window and therefore reached the criteria for ready biodegradability
Overall conclusion:
The fact that the test item reached the criteria for ready biodegradability in two of three replicates and in the toxicity control justifies the declaration of the test item as ready biodegradable.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Overall conclusion:
The fact that the test item reached the criteria for ready biodegradability in two of three replicates and in the toxicity control justifies the declaration of the test item as ready biodegradable.

Executive summary:

The degradation of the test item at the end of the test was 74.3% (d 42 after acidification, mean of three replicates).

In two replicates (reactors 15 and 16), the degradation started after a lag-phase of 14 days and reached a value of >60% by day 26 (see table 3). Since a mean degradation of 10% in those two replicates was reached on day 17, the degradation of >60% was reached within a 10-d window.

Therefore, in two of three replicates, the criteria for ready biodegradability were reached (60% of ThCO₂within a 10-d window).

In one replicate (reactor 14) the degradation started after a lag-phase of 22 days and reached a value of >60% by day 35 (see table 4). Since a degradation of 10% was in this replicate reached on day 25, the degradation of >60% was also reached within a 10-d window.

Since a degradation of 60% was reached beyond 28 days, this replicate did not reach the criteria for ready biodegradability but the criterion for non-persistence (60% of ThCO₂within 60 days).

In the toxicity control, the test item was also degraded by more than 60% within 28 days and within a 10-d window (see‎6.1.2).

Description of key information

The fact that the test item reached the criteria for ready biodegradability in two of three replicates and in the toxicity control justifies the declaration of the test item as ready biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable