Orthoboric acid, compound with 2,2',2''-nitrilotriethanol

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:

6th July 2017 to 10th August 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Version / remarks:

OECD, 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Purity: 88% Test Item, 12% Water

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

An inoculum containing an active microbial population was prepared as follows. Six days prior to test initiation, a sample of secondary effluent was collected from the Guelph Wastewater Treatment Plant (Guelph, Ontario). The Guelph Wastewater Plant treats sewage of predominantly domestic origin .The secondary effluent was continuously aerated during transport to, and storage at AquaTox, and then pre-conditioned for testing. During preconditioning, the secondary effluent was maintained at test temperature (22 ± 2 °C) prior to test initiation. The secondary effluent was settled for 30 minutes prior to the clear supernatant being decanted for use as the inoculum.

Duration of test (contact time):

35 d

Initial conc.:

3.87 mg/L

Based on:

test mat.

Initial conc.:

4 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The test involved exposure of an active microbial population (secondary effluent from a wastewater treatment plant) to the test item under constant temperature in the dark. The test is typically terminated on the 28th day; however, the test was extended by an additional 7 days since acclimation of the bacteria to the test item occurred late in the test. Initial oxygen demand for the test item was determined from the Chemical Oxygen Demand (COD) The test item was evaluated at approximately 4.0 mg COD test item/L in a series of test chambers. During the test, the bacteria utilize a nutrient solution (devoid of carbon) and the test item (the carbon source), consuming dissolved oxygen in the process. The dissolved oxygen from each biodegradation test vessel was measured with an oxygen electrode on a frequency adequate to track the degradation of the test item (i.e., on days 0, 4, 7, 14, 21, 28 and 35). The test was terminated on the 35th day.

The amount of oxygen consumed within the test system was compared to the COD of the test substance and the percent (%) degradation was calculated. The 35-day biodegradation curve for the test item was prepared using calculations prescribed in the test method and by graphical representation. The degradation rates of the test item and degradation values for any point in time were calculated and reported to the nearest 0.1%.

To monitor nitrification during the test, samples were collected from all test and inoculated control solutions at each sampling period (single sample for each of nitrate and nitrite). Samples (approximately 10 mL) were collected in 15-mL plastic centrifuge tubes and submitted for analysis.

Reference substance:

other: Potassium Hydrogen Phthalate (KHP)

Remarks:

KHP, which does not degrade in the absence of an inoculum within the duration of the test, was selected over the reference substances recommended by OECD (1992) which will degrade in water in the absence of an inoculum

Test performance:

The test item achieved 70.0% degradation over the 35-day exposure.

• The reference substance achieved >60% degradation within 14 days of test initiation
• The difference of extremes of replicate values of the removal of the test item at the plateau, and at the end of the test, was less than 20%.
• Inoculated control (nutrient blank) did not exhibit more than 1.5 mg/L reduction in dissolved oxygen concentration.
• The residual dissolved oxygen concentration in the test vessels did not fall below 0.5 mg/L.
• Inhibition of the microbial population was not observed (i.e., >25% degradation in 14 days).

Key result

Parameter:

% degradation (O2 consumption)

Value:

70

Sampling time:

35 d

Remarks on result:

other:

Details on results:

Reference Series (Procedural Control)
The reference item achieved 86.2% degradation in 14 days, thereby meeting the pass criteria of ≥ 60% within 14 days.
Therefore, the test system was acceptable for the determination of biodegradability.
Percent Biodegradation of the Reference Substance After 14 and 35 Days
Duration (Days) Percent Degradation
14 86.2
35 86.2
* The percentage degradation is the average of two replicates.

Inhibition Series (Toxicity Control)
Inhibition of the microbial population was not observed (i.e., >25% degradation in 14 days)
Percent Biodegradation in the Inhibition Test After 14 and 35 Days
Duration (Days) Percent Degradation
14 43.1
35 85.6
* The percentage degradation is the average of two replicates.

Test Item Series (Test Suspension)
Estimate of the Ready Biodegradability of the Test Item After 28 and 35 Days
Test Item Degradation (%) after 28 35 days
TEA BORATE 36.0 70.0
* The percentage degradation is the average of two replicates.

NITRATE AND NITRITE ANALYSIS.
The concentrations of nitrite and nitrate in the test solutions (T-1, T-2) were below the detection limits of 0.01 mg/L and 0.1 mg/L, respectively during the first 14 days of the test. However, corrections to the dissolved oxygen concentrations were required for some of the measured
values for T-1 on days 21, 28 and 35 and for T-2 on day 35.
Measured nitrite and nitrate concentrations of the control (S-1, S-2) and test (T-1, T-2) solutions measured during the 35-day exposure.
Date Day Nitrite Nitrate Nitrite + Nitrate
S-1 S-2 T-1 T-2 S-1 S-2 T-1 T-2 S-1 S-2 T-1 T-2
2017-07-06 0 <0.01 - <0.01 - <0.1 - <0.1 - <0.1 - <0.1 -
2017-07-10 4 <0.01 <0.01 <0.01 <0.01 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
2017-07-13 7 <0.01 <0.01 <0.01 <0.01 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
2017-07-20 14 <0.01 <0.01 <0.01 <0.01 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1
2017-07-27 21 <0.01 <0.01 0.101 <0.01 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.17 <0.1
2017-08-03 28 0.029 0.028 0.252 0.020 0.12 0.12 0.11 0.11 0.15 0.15 0.36 0.13
2017-08-10 35 0.090 0.043 0.338 0.274 <0.1 0.12 0.11 <0.1 0.19 0.16 0.45 0.36
- Not sampled

Comment;
The accuracy of the dissolved oxygen meter is +/-2%

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable, not fulfilling specific criteria

Conclusions:

The pecentage degradation obtained by the test item in the first 28 days was 36%. Therefore, the test item is not considered to be readily biodegradable according to OECD Guideline 301D (i.e., did not achieve 60% degradation within the 28-day test period).

Executive summary:

The study was conducted in accordance with the OECD 301 D Biodegradability Closed Bottle Test guideline to investigate the ready biodegradability of the test item. The test exposes microorganisms to the test items, which they utilise as carbon source. The test involved exposure of an active microbial population (secondary effluent from a

wastewater treatment plant) to the test item for 35 days under constant temperature in the dark.

The test duration was extended beyond 28 days to Day 35 due to an extended lag phase where acclimation of

the bacteria to the test item occurred late during the test.

Initial oxygen demand for the test item was determined from the Chemical Oxygen Demand (COD). The test item was evaluated at approximately 4.0 mg COD test item/L in a series of test chambers. During the test, the bacteria utilize a nutrient solution (devoid of carbon) and the test item (the carbon source), consuming dissolved oxygen in the process. The dissolved oxygen from each biodegradation test vessel was measured with an oxygen electrode on a frequency adequate to track the degradation of the test item (i.e., on Days 0, 4, 7, 14, 21, 28 and 35). The test was terminated on the 35th day. The amount of oxygen consumed within the test system was compared to the COD of the test substance and the percent (%) degradation was calculated. The 35-day biodegradation curve for the test item was prepared using calculations prescribed in the test method and by graphical representation. The degradation rates of the test item and degradation values for any point in time were calculated and reported to the nearest 0.1%.

The percentage degradation obtained by the test item in the first 28 days was 36.0%. Therefore, the test item is considered to be non rapidly biodegradable according to the CLP crietria for classification and labelling.

NOTE: Any of data in this dataset are disseminated by the European Union on a right-to-know basis and this is not a publication in the same sense as a book or an article in a journal. The right of ownership in any part of this information is reserved by the data owner(s). The use of this information for any other, e.g. commercial purpose is strictly reserved to the data owners and those persons or legal entities having paid the respective access fee for the intended purpose.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria