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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-11-22 to
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
July 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
CAS No.: 7665-72-7
Batch No.: ZMG-195668
Appearance: Clear colourless liquid
Molecular formula: C7H14O2
Storage conditions: Cool, protected from light
Expiry date: 07 March 2019
Purity: 99.8%
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): municipal wastewater treatment plant Breisgauer Bucht. The treatment plant clarifies predominantly domestic wastewater and has a capacity of 600.000 inhabitant equivalents. -
- Sampling date of activated sludge: 2017-11-28
- Concentration of sludge: 30 mg dry solids per litre. The dry solids content of the activated sludge was 4.7 g/L. It was determined by weight measurements after drying at 105°C for 3.25 hours (mean of triplicate measurements).

Duration of test (contact time):
28 d
Initial conc.:
108.4 mg/L
Based on:
ThOD
Remarks:
The test item was added directly into the test vessels. Therefore 7.6 µL of the test item was added to the test vessels corresponding to a concentration of 108.4 mg ThOD/L.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of mineral medium:
a) 8.50 g KH2PO4, 21.75 g K2HPO4, 33.40 g Na2HPO4 * 2 H2O, were dissolved in demineralised water and made up to 1 litre.
b) 36.4 g CaCl2 * 2H2O was dissolved in demineralised water and filled up to 1 litre.
c) 22.5 g MgSO4 * 7H2O was dissolved in demineralised water and filled up to 1 litre.
d) 0.25 g FeCl3 * 6H2O was dissolved in demineralised water, stabilised with one drop of concentrated HCl and filled up to 1 litre

For preparation of the mineral medium 10 mL of solution (A) is mixed with 900 mL demineralised water, 1 mL each of solutions (B), (C) and (D) are added and the volume is made up to 1 litre.
Before use, the mineral medium is aerated for about one hour and the pH is if necessary adjusted to 7.4 ± 0.2.

- Test temperature: 21.5 - 21.9 °C
- pH: 7.4
- Suspended solids concentration: 30 mg/L

TEST SYSTEM
- Test system: OxiTop®- Control from WTW, Weilheim and the Sensomat-System from Aqualytic GmbH & Co., Langen: They consist of narrow-necked glass bottles with rubber sleeve inserts for NaOH pellets, in which the carbon dioxide evolved is absorbed. The liquid volume was fixed as 164 mL each. Magnetic stir bars were introduced into the bottles which were positioned on a stirrer platform. The bottles were sealed tightly with the measuring heads with a measuring range of 500 – 1350 hPa. Every 112 minutes the current pressure was measured and stored by each measuring head. At the end of the experiment pressure data were read out via an infrared interface to the controller unit and afterwards data were transferred via a RS232 interface using the Achat OC software of WTW to an Excel file where further data processing was carried out. Additionally several measured values were randomly read out and recorded by hand and were afterwards compared with the printed excel table for quality control.
- Preparation of Test flask: test item was added directly into the test vessels

SAMPLING
- Sampling frequency: on the 4th, 8th, 12th, 16th, 20th, 24th and 28th day as well as beginning and end of study

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates
- Abiotic control: 1
- Toxicity control: 1 replicate
- Reference compound: 3 replicates
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
7
Sampling time:
28 d
Remarks on result:
other: mean of three replicates
Details on results:
The pass level for ready biodegradability is 60% of ThCO2 and must be reached within a 10 day window (which begins when the degree of biodegradation reaches 10%).
- Biodegradation of the test item: Only very slight degradation of the test item could be observed during the test duration (28 days after acidification). The test item did not reach the criteria for ready biodegradability according to the OECD criteria.
- Biodegradation of the Toxicity Control: The degradation in the toxicity control reached a value higher than 25% within 4 days (see table 2). According to the validity criterion of the guideline OECD 301 the test item had no toxic effect to the inoculum.
- Abiotic control: There was no degradation observed in the abiotic control.

Summary of results: Please refer to the tables below, shown in "Any other information on results incl. tables"
Results with reference substance:
The reference compound sodium acetate reached the pass level for ready biodegradability (60% ThOD within a 10-day window) within 4 days
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
There was only a minor biodegradation of the test item observed within 28 days, the degradation extent at the end of the test was 7.0% (mean of three replicates).
Therefore the test item did not reach the pass level for ready biodegradability (60% ThOD within 28 days and 10 d-window).
Executive summary:

The biodegradation of Tert-Butyl glycidyl ether was studied in a suspension in mineral medium inoculated with activated sludge (30 mg suspended solids/L). The experiment was conducted in accordance with the OECD test guideline 301 F "Manometric Respirometry Test" and in compliance with the OECD-GLP standards.

The system OxiTop®- Control from WTW, Weilheim and the Sensomat-System from Aqualytic GmbH & Co., Langen were used as test systems. They consist of narrow-necked glass bottles with rubber sleeve inserts for NaOH pellets, in which the carbon dioxide evolved is absorbed. The liquid volume was fixed as 164 mL each. Magnetic stir bars were introduced into the bottles which were positioned on a stirrer platform. The bottles were sealed tightly with the measuring heads with a measuring range of 500 – 1350 hPa. Every 112 minutes the current pressure was measured and stored by each measuring head.

Tert-Butyl glycidyl ether never reached the pass level for ready biodegradability (60% ThOD in a 10-day window, which begins when the degree of biodegradation reaches 10%). Only slight degradation of the test item could be observed during the test duration (28 days after acidification).

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
1978-10-27 to 1979-01-15
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)
GLP compliance:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
The test material was submitted to the Environmental Sciences Research Laboratory by E. Ward, Oxides and Intermediates TS&D, for environmental screening test
- Source and lot/batch No.of test material: lot number 04078 (XAS-1467)
- Purity: 99.20 %
- Sample composition: t-BGE (99.20 %), t-butoxy-2-propanol (0.34 %), tri-isobutylene (0.14 %), t-butanol (0.10 %), unidentified (0.22 %)
- Physical state: clear liquid, stable during test conditions
- Solubility in water: 40 g/L at 25 °C
Oxygen conditions:
aerobic
Inoculum or test system:
other: Wastewater Treatment Plant
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): 1. Michigan Division's 437 Wastewater Treatment Plant. 2. City of Midland Wastewater Treatment Plant (before chlorination).
- Laboratory culture:
- Method of cultivation:
- Storage conditions:
- Storage length:
- Preparation of inoculum for exposure:
- Pretreatment:
- Concentration of sludge: The seeds were used at concentrations of 55 mL and 45 mL of effluent per liter of seed solution
- Initial cell/biomass concentration:
- Water filtered: yes/no
- Type and size of filter used, if any:
Duration of test (contact time):
20 d
Initial conc.:
40 g/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: standard 20-day BOD test
Details on study design:
TEST CONDITIONS
- Composition of medium:
- Additional substrate:
- Solubilising agent (type and concentration if used):
- Test temperature:
- pH:
- pH adjusted: yes/no
- CEC (meq/100 g):
- Aeration of dilution water:
- Suspended solids concentration:
- Continuous darkness: yes/no
- Other:
- Aeration: 4 hours

TEST SYSTEM
- Following tests were conducted: total oxygen demand (TOD-Dow analyzer), chemical oxygen demand (COD-potassium dichromate and alkaline potassium permanganate methods), biochemical oxygen demand (BOD), air stripping (aeration)
- Culturing apparatus:
- Number of culture flasks/concentration:
- Method used to create aerobic conditions:
- Method used to create anaerobic conditions:
- Measuring equipment:
- Test performed in closed vessels due to significant volatility of test substance:
- Test performed in open system:
- Details of trap for CO2 and volatile organics if used:
- Other:

SAMPLING
- Sampling frequency:
- Sampling method:
- Sterility check if applicable:
- Sample storage before analysis:
- Other:

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

STATISTICAL METHODS:
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
20 d
Key result
Parameter:
% degradation (test mat. analysis)
Value:
3
Sampling time:
4 h
Key result
Parameter:
ThOD
Value:
2.25 other: mg O2/L of test solution
Parameter:
COD
Value:
2.22 other: p/p
Remarks on result:
other: Acidic K2Cr2O7 Method
Parameter:
COD
Value:
0.68 other: p/p
Remarks on result:
other: Basic KMnO4 Method
Parameter:
BOD5
Value:
0 other: p/p
Remarks on result:
other: Municipal Seed
Parameter:
BOD5
Value:
0 other: p/p
Remarks on result:
other: Industrial Seed

Table 1 Aeration Test

Time (hr) % Removed
0.5 0.5
1 0.5
2 2.4
4 3.0
Conclusions:
The high water solubility of the title material (40 g/L) makes bioconcentration unlikely. Three percent of the title material was removed from water after four hours of aeration (concentration monitored by TOD analysis).
The test material consumed no oxygen in the standard 20-day BOD test. It would not be expected to degrade in a conventional biological wastewater treatment plant. If the use pattern of t-BGE suggests that it may be discharged in large quantities to the aquatic environment, or to a wastewater treatment plant, a more definitive biodegradation study should be considered.

Tertiary butyl glycidyl ether's high water solubility and low removal by aeration indicate that water will be its principal mode of environmental movement. Using the correlations between water solubility, octanol-water partition coefficient, and bioconcentration factor noted by previous workers, the bioconcentration potential of t-BGE in the aquatic environment is estimated to be low.

If the use pattern of t-BGE suggests that it may be discharged in large quantities to the aquatic environment, or to a wastewater treatment plant, a more definitive biodegradation study should be considered.
Executive summary:

t-BGE consumed no oxygen in the 20-day BOD test. Due to the deficiencies of the report (no guideline), no clear conclusions on the stability of the substance in terms of biodegradation can be drawn.

Description of key information

t-BGE consumed no oxygen in the 20-day BOD test. Due to the deficiencies of the report (no guideline), no clear conclusions on the stability of the substance in terms of biodegradation can be drawn. Therefore a subsequent OECD biodegradation study has been carried out. In the course of this study the biodegradation of tert-Butyl glycidyl ether (determined according to OECD guideline 301 F) within 28 days was 7 % of ThOD (mean of three replicates). The test item did not reach the criteria for ready biodegradability (60 % ThOD within a 10-d window).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information