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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:
17 Mar - 14 Apr 1987
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
adopted in 1984
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: obtained from municipal laboratory wastewater treatment plant (16 Mar 1987)
- Concentration of sludge: 30 mg/L (in test)
Duration of test (contact time):
28 d
Initial conc.:
52 - 200 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Number of culture flasks/concentration: 100 mg/L: 3 replicats; 52/200 mg/L: two replicats
- pH: 6.8 - 7.8

CONTROL AND BLANK SYSTEM
- Toxicity control: yes
Reference substance:
aniline
Remarks:
100 mg/L
Parameter:
% degradation (O2 consumption)
Value:
90 - 100
Sampling time:
28 d
Details on results:
- lag phase 3 day
- > Manometric Respirometry test60% degradation after 10 days
- biodegradation degree after 28 days: >90%
The test substance is readily biodegradable.
Parameter:
COD
Value:
1 687 mg O2/g test mat.
Parameter:
BOD5
Value:
277 mg O2/g test mat.
Results with reference substance:
100% DOC elimination in 10 days

The toxicity control indicates that the test substance is not inhibitory to activated sludge microorganisms (> 90% degradation after 14 days)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance reached a biodegradation of 90 - 100% in 28 days. The 10-day-window was passed. Therefore, the test substance is readily biodegradable according to OECD criteria.
Executive summary:

The ready biodegradability of Bis(2-ethylhexyl) adipate was tested according to EU method C.4-D (manometric respirometry test equivalent to OECD 301F) under GLP conditions. Non-adapted municipal activated sludge was used as inoculum. The test substance was tested at concentrations between of 52 and 200 mg/L. The validity criteria are fulfilled. The pass level of 60% biodegradation was reached in less than 10 days. After 28 days a biodegradation of 90 – 100 % was observed. Therefore, the test substance is readily biodegradable according to OECD criteria.

Description of key information

Readily biodegradable (according to OECD criteria): > 90% in 28 days (OECD 301F)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Several studies investigating the ready biodegradability of Bis(2-ethylhexyl) adipate (DEHA, CAS 103-23-1) are available.

Ready biodegradabilityof DEHA

The key study was performed under GLP conditions in a manometric respirometry test according to EU method C.4-D (equivalent to OECD 301F) (BASF 1987). Non-adapted domestic activated sludge was used as inoculum. The validity criteria were fulfilled. The pass level of 60% biodegradation was reached in less than 10 days. After 28 days a biodegradation of 90 – 100 % was observed. Thus, DEHA is readily biodegradable according to OECD criteria.

This result is confirmed by a QSAR calculation using BIOWIN v4.10, which predicted the ready biodegradability of the test substance (BPCN 2014), and six additional experimental results, which are used as supporting information only since original reports are not available (METI 1994, Hüls 1996) or adapted inoculum was used (Felder et al. 1986, Saeger et al. 1976). One study was performed by the Japanese Ministry of Economy, Trade and Industry according to OECD guideline 301C (METI 1994). 100 mg test substance /L was applied. Based on O2 consumption a biodegradation of 67 – 74% was reached after 28 days.

A second study was performed according EU method C.4-C and GLP using non-adapted domestic activated sludge as inoculum (Hüls 1996). 21 mg test substance /L was applied. The pass level of 60% biodegradation was reached in less than 10 days. After 28 days a biodegradation of 83% was observed.

 

Felder et al. (1986) and Saeger et al. (1976) investigated the inherent biodegradability of DEHA using on the one hand the semi-continuous activated sludge method (similar to OECD 302A) and on the other hand a 35d CO2 evolution test according to Thomson and Duthie (1968) and Sturm (1973). Both tests were performed with adapted inoculum. SCAS studies were carried out by a procedure described previously (SDA 1965) with suggested feed (Mausner et al. 1969) in magnetically stirred 1.5 L glass vessels. Activated sludge was obtained from a local domestic sewage treatment plant. Acclimation of the activated sludge was carried out by an incremental feeding schedule for each unit during the first 3 weeks (1, 3, and 5 mg/24h cycle). After the acclimation period, the primary biodegradation rate was determined each weak by analyzing 50 mL liquor samples withdrawn after feeding and at the end of the aeration cycle. Degradation was measured initially at a feed level of 5 mg (3.3 mg/L), and then this level was increased to 20 mg (13.3 mg/L). Disappearance of the test substance was measured by GC. Primary degradation of 65 - 96% and of 73 – 92% was observed by Felder et al. (1986) and Saeger et al. (1976), respectively.

Carbon dioxide evolution studies were carried out by the Sturm modification (Sturm 1993) of the Thompson and Duthie procedure (Thompson and Duthie 1968) (T-D-S) and a shake flask system similar to that described by Gledhill (1975). The seed for both systems was prepared by a 14-day die-away procedure (Bunch and Chambers 1967). A 2 L flask containing 20 mg of test material, 50 mg of yeast extract, 100 mL of settled SCAS supernatant, and 900 mL of standard biological oxygen demand (BOD) dilution water was prepared and stored in the dark under static conditions. Settled SCAS supernatant from a blank unit was employed in the seed preparation. Ultimate degradation of 94% and of 93.8% (81.6% shake flask method) was observed by Felder et al. (1986) and Saeger et al. (1976), respectively.

Based on the available it can be concluded that Bis(2 -ethykhexyl) adipate is readily biodegradable according to OECD criteria.

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