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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August 2005 - October 2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Test material: REACH substance in aqueous solution = commercial product
- Analytical purity: 48.7%
- Purity test date: Not specified
- Lot:bacth No.: WI6G16X07
- Expiration date of the lot/batch: July 2006
- Appearance: Yellowish viscous liquid
- Storage: At room temperature
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Domestic activated sludge was collected from the Galt Wastewater Treatment Plant, Cambridge, Ontario on August 9, 2005. The sludge was gently aerated for 2.25 hours and then settled for 0.5 hours prior to the supernatant being filtered through a 5.0-µm filter. The filtered supernatant was added to the mineral medium.
Duration of test (contact time):
28 d
Initial conc.:
8.5 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:
TEST CONDITIONS
- Composition of medium: Reagent water with nutrients
- Test temperature: 22 ± 1 °C
- pH: 7.4 ± 0.2
- pH adjusted: No
- Aeration of dilution water: None
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 300-ml BOD bottles
- Number of culture flasks/concentration: 2
- Measuring equipment: Oxygen electrode

SAMPLING
- Sampling frequency: On Days 0, 7, 14, 21 and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: Yes
- Toxicity control: Yes

Reference substance:
other: Phthalic acid
Key result
Parameter:
% degradation (O2 consumption)
Value:
63.3
Sampling time:
14 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
78.5
Sampling time:
28 d
Details on results:
INHIBITION SERIES
The inhibition series demonstrated that the test item was not toxic to the bacterial inoculum (> 25% biodegradation after 28 days).

DEFINITIVE TEST SERIES
Changes in oxygen concentration due to nitrification were calculated based on changes in nitrate and nitrite in test and contrOL solutions sampled at the beginning and end of the 28-day biodegradability evaluation. Changes in dissolved oxygen due to nitrification/denitrification in the test and contrOL solutions were minimal (-0.217 mg/L). The 28-day oxygen concentrations for the test item were corrected for this gain in oxygen. The test item achieved 63.3% biodegradation in 14 days, and 78.5% biodegradation in 28 days.
Results with reference substance:
The reference substance (phthalic acid) achieved 86.8% biodegradation within 14 days and maintained this approximate level of biodegradation over the 28-day test, satisfying the acceptability criterion (i.e., 60% biodegradation in 14 days). Reference test results indicate that the bacterial inoculum and test system were acceptable for the determination of ready biodegradability.

 Table 1: Oxygen determinations (mg/L)

 

 

Vessel

Measured O2 concentrations

Day

0 hours

7

14

21

28

Control:     
                            C1


8.800


8.100


8.150


8.167


8.000

Inoculated control:

                           S1
                           S2
                     Mean


8.700
8.600
8.650


7.900
7.900
7.900


7.950
7.950
7.950


8.100
8.150
8.125


7.400
7.700
7.550

Test item:

                           T1
                           T2
                     Mean


8.500
8.500
8.500


5.700
5.800
5.750


5.300
5.500
5.400


5.300
5.500
5.400


4.486 *
4.286 *
4.386

Reference substance:

                           R1
                           R2
                     Mean


8.600
8.700
8.650


4.700
4.700
4.700


4.550
4.400
4.4475


4.500
4.400
4.450


4.100
4.100
4.100

Inhibtion control:

                           I1
                           I2
                     Mean


8.400
8.500
8.450


3.300
3.500
3.400


2.850
2.600
2.2725


2.400
2.600
2.500


1.900
2.000
1.950

 

* : The day 28 measured oxygen concentration in T1 and T2 were 4.7 and 4.5 respectively. The day 28 oxygen concentration in the test solutions were corrected by a 0.214 mg/l gain in oxygen to the test system due to notrification. No other data were corrected for nitrogen content.

 

 Table 2: Oxygen depletions (mg/l)

 

 

Vessel

Oxygen depletions

Day

0

7

14

21

28


Test item


N/A


2.150


2.550


2.725


3.164


Reference substance


N/A


3.200


3.475


3.675


3.450


Inhibition control


N/A


4.500


5.225


5.625


5.600

Note: Oxygen depletions were calculated by subtracting the mean oxygen concentration of the test item, reference, and inhibition series, respectively, from the mean oxygen concentration of the inoculated control.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item achieved ≥ 60% degradation within 14 days after achieving 10% degradation (14-day window).
Executive summary:

The ultimate aerobic biodegradability of the test item (= REACH substance in aqueous solution) was investigated in a GLP-compliant ready biodegradability screening study performed in accordance with OECD Guideline No. 301D. The test item achieved 60% degradation in 28 days, and ≥ 60% degradation within 14 days after achieving 10% degradation (14-day window). The test item is thus considered 'readily biodegradable'.

Description of key information

The ultimate aerobic biodegradability of the test item (= REACH substance in aqueous solution) was investigated in a GLP-compliant ready biodegradability screening study performed in accordance with OECD Guideline No. 301D. The test item achieved ≥ 60% degradation in 28 days, and ≥ 60%degradation within 14 days after achieving 10% degradation (14-day window). The test item is thus considered 'readily biodegradable'.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The ready biodegradability of the test item was investigated in one GLP-compliant study performed in accordance with standard methods, without deviations. The study is considered as reliable (Klimisch 1) and is selected as a key study for the endpoint.