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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:
20 Oct 1992 to 17 Nov 1992
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
1981
Qualifier:
according to
Guideline:
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-hydroxyethyl acrylate
- Analytical purity: >98%
- Lot/batch No.: EB 920322
- Description: colourlessl liquid
- Container: brown glass bottle
- Storage conditions: room temperature
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: A mixed population of activated sludge micro-organisms was obtained on 20 Oct 1992 from Severn Trent PLC sewage treatment plant at Belper, Derbyshire, U.K, which treats predominantly domestic sewage.
- Preparation of inoculum for exposure: The activated sludge sample was continuously aerated in the laboratory at a temperature of 21 °C. The sample was then homogenized in a mixer for 10 minutes and allowed to settle. The solids were then removed by centrifuging and the supernatant maintained under aerobic conditions until used in the study.
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
test mat.
Initial conc.:
20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Test temperature: 21 ± 1 °C
- Aeration: Each culture vessel was aerated with CO2-free air bubbled through the solution at a rate of approximately 2 bubbles per second
- Stirring: Each culture vessel was stirred continuously by a magnetic stirrer
- Activated sludge concentratioin: Filtrate of activated sludge (Inoculum) from a sewage treatment plant was added to the each culture vessels at a final concentration of 1%.
- Continuous darkness: yes

COMPOSITION OF MEDIUM
- Solution 1: FeC13·6H20, 0.25 g/L
- Solution 2: MgSO4·7H20, 22.5 g/L
- Solution 3: CaCl2, 27.5 g/L
- Solution 4: (NH4)2SO4, 40.0 g/L
- Solution 5: KH2PO4, 8.5 g/L; K2HPO4, 27.75 g/L; Na2HPO4·7H20, 33.4 g/L; NH4Cl, 1.7 g/L
- To 1 litre of purified water (ion exchange and reverse osmosis treated tap water) is added the following volumes of solutions 1 - 5: 4 mL, 1 mL, 1 mL, 1 mL and 2 mL

TEST SYSTEM
- Culturing apparatus: 5-liter glass culture vessels
- Test volume: 3 liter
- Number of culture flasks/concentration: 2
- Test performed in closed vessels: yes

SAMPLING
- Sampling frequency: samples from the first CO2 absorber vessel of each culture vessel were taken at the test start and on days 1, 2, 3, 6, 8, 10, 14, 16, 21, 23, 27 and 28. The second CO2 absorber vessel was sampled on days 0 and 28 only.
- Sampling method: The carbon dioxide produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. On day 27 of the study the pH of each culture vessel was recorded and 1 ml of concentrated hydrochloric acid was added to drive off inorganic carbonate. The culture vesseis were resealed, aerated overnight and the final samples for CO2 analysis taken from both absorber vesseis on Day 28.

CONTROL AND BLANK SYSTEM
- Inoculum blank: conisted of nutrient medium and activated sludge
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
79
Sampling time:
28 d
Remarks on result:
other: 10 mg/L test substance
Key result
Parameter:
% degradation (CO2 evolution)
Value:
80
Sampling time:
28 d
Remarks on result:
other: 20 mg/L test substance
Details on results:
- Lag time: Day 0 to day 3 for both the concentration (10 mg/L and 20 mg/L).
- Time required for 10% degradation: Approximately 10% biodegradation occurred on  ~ 6.5 & ~ 8.2 days , at the 10 & 20 mg/L concentration respectively.
- Maximum biodegradation occurred between 10 to 14 days for 10 & 20 mg/L concentration.
For an overview of test results, see 'Any other information on materials and methods incl. tables'.
Results with reference substance:
The reference substance attained 94% degradation after 28 days.

Table: Percentage biodegradation values (%)

Days

RS

TM1 (10 mg/L)

TM2 (20 mg/L)

0

0

0

0

1

0

0

0

2

20

0

0

3

32

0

0

6

58

6

2

8

80

30

7

10

88

44

28

14

91

74

57

16

91

75

60

21

95

78

77

23

92

85

77

27

90

80

77

28

94

79

80

RS = reference substance

TM: test material

Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
13 Mar 1996 to 10 Apr 1996
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)
Version / remarks:
July, 1992
GLP compliance:
yes
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-hydroxylethyl acrylate
- Molecular formula (if other than submission substance): C5H8O3
- Molecular weight (if other than submission substance): 116.1
- Physical state: liquid
- Analytical purity: 97%
- Storage condition of test material: cool, dark
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: secondary effluent collected from the Downingtown Regional Water Pollution Control Center, Pensylvania
- Pretreatment: The effluent was allowed to settle for one hour. The supernatant was decanted and used as the inoculum.
Duration of test (contact time):
28 d
Initial conc.:
3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Test vessels: closed
- Test temperature: 20.0 - 20.1 °C
- Dilution water: Deionized water containing one milliliter of the following standard reagent solutions per liter.
- magnesium sulfate solution, 2.25%
- calcium chloride solution, 2.75%
- phosphate buffer, pH 7.2 at 25°C
- ferric chloride solution, 0.025%
- Aeration of dilution water: yes to ca. 9 mg/L
- Continuous darkness: yes
- Replicates: 1 at test initiation, 2 at the other sampling times.

SAMPLING
- Sampling frequency: at test initiation and at day 7, 14, 21 and 28.
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
32.9
Sampling time:
28 d
Details on results:
The test compound was degraded for 32.9% after 28 days of incubation.
Results with reference substance:
ThOD (28d) = 89.8%

Test results:

 

Initial DO (mg/L)

Mean final DO (mg/L)

% ThOD (28d)

Sodium benzoate

8.9

3.8

89.8

Hydroxyethyl acrylate

9.0

7.0

32.9

Validity criteria fulfilled:
not specified
Interpretation of results:
not readily biodegradable
Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, industrial, non-adapted
Duration of test (contact time):
15 d
Initial conc.:
400 mg/L
Parameter followed for biodegradation estimation:
DOC removal
Parameter:
% degradation (DOC removal)
Value:
95
Sampling time:
15 d
Details on results:
Adsorption after 3 hrs: ca. 10 %
Interpretation of results:
inherently biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))
Version / remarks:
May, 1981
GLP compliance:
no
Specific details on test material used for the study:
- Name of test material (as cited in study report): 2-Hydroxyethyl acrylate
Oxygen conditions:
aerobic
Inoculum or test system:
mixture of sewage, soil and natural water
Details on inoculum:
- Source of inoculum/activated sludge: In March, June, September, and December, sludge was sampled at the following 10 places in Japan:
1. Fukogawa city sewage plant,
2. Fukashiba industry sewage plant,
3. Nakahama city sewage plant,
4. Ochiai city sewage plant,
5. Kitakami river,
6. Shinano river,
7. Yoshino river,
8. Lake Biwa,
9. Hiroshima bay,
10. Dookai bay;
- Sampling: 1.
City sewage: Returned sludge from sewage plants was taken.
2. Rivers, lake and sea: Surface water and surface soil which were in contact with atmosphere were collected.
- Method of cultivation: About 30 minutes after ceasing aeration to the sludge mixture, supernatant corresponding to about 1/3 of the whole volume was removed. Then the equal volume of dechlorinated water was added to the remaining portion and aerated again, followed by addition of synthetic sewage at a concentration of 0.1% (w/v). This procedure was repeated once every day. The culturing was carried out at 25 ± 2 °C. 5 L of the filtrate of the supernatant of old activated sludge was mixed with 500 mL of the filtrate of the supernatant of new sludge and cultured at pH 7.0 ± 1.0 under sufficient aeration using prefiltered open air. During the cultivation, appearance of the supernatant, precipitability, formation of flock, pH, dissolved oxygen concentration in the solution and temperature were checked and necessary adjustments were made, Microflora in the activated sludge was microscopically observed and sludge with no abnormal symptom was used for the test.
- Concentration of sludge: 30 mg/L
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: 3 mL each of four stock solutions, as described in JIS K 0102-1986-21, are diluted to 1000 mL with purified water
- pH: 7.0
- pH adjusted: yes
- Suspended solids concentration: determined according to Method Japanese Industrial Standards (JIS) K 0102-1986-14.1

TEST SYSTEM
- Culturing apparatus: Closed system oxygen consumption measuring apparatus (Coulometer: Ohkura Electric Co., Ltd.); 300 mL vessel, absorbent for evolving carbon dioxide Soda lime No .l (extra pure reagent, Wako Pure Chemical Industries, Ltd.).
- Number of culture flasks/concentration: 1
- Measuring equipment: Coulometer, Okhura Electric Co., Ltd.
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: soda lime, extra pure, Wako Pure Chemical Industries, Ltd.)

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: no
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
78
Sampling time:
28 d
Remarks on result:
other: 76 - 80%
Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable

Description of key information

The test substance is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradability of 2-hydroxyethyl acrylate was tested in accordance with OECD guideline 301B, 301D, 301C and 302B. Readily biodegradability of the test substance was monitored after 28 days with degradation rates of 79 and 78 percent measuring CO2 evolution (301B) and O2 consumption (301C), respectively. In addition, 2-hydroxyethyl acrylate was tested in a closed bottle test performed in accordance with OECD guideline 301D (3 mg/L), attaining 30 - 40 % BOD of ThOD within 28 days (BAMM 1996). Based on the presented test results, 2-hydroxyethyl acrylate is considered to be readily biodegradable. This assessment is supported by the result of an investigation on the inherent biodegradability of the substance. In this investigation the inherent biodegradability of 2-hydroxyethyl acrylate was shown after 15 days of exposure (95 %).