Fast Pyrolysis Bio-oil

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:

08 May 2013 - 03 July 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg, Germany

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

As inoculum, activated sludge collected from the aeration tank of the municipal sewage treatment plant of Pforzheim/Germany was used. This sewage treatment plant treated predominantly domestic sewage. The activated sludge was washed in mineral medium for three times by centrifugation at 3000 rpm for 10 minutes and was afterwards kept under aerobic conditions for 2 days prior to application. The concentration of activated sludge was adjusted to 20 mg/L in the test bottles.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Test System:
The test was performed in accordance with OECD Guideline 301 F.
The mineral medium was inoculated with a defined amount of activated sludge from a municipal waste water treatment plant. 500 mL brown glass bottles served as reaction vessels. These were filled with 250 mL permanently stirred test media, and respective chemicals.
All reaction vessels were stored in an incubator BSB-Digi device (Selutec GmbH, 72379 Hechingen, Germany) ensuring a constant temperature (22 °C ± 1 °C) and continuous agitation. The system consisted of a reaction vessel containing a CO2 absorbing agent (soda lime) , an electro-chemical oxygen generator and a switching manometer. The amount of produced oxygen required to maintain constant gas volume was determined via coulometry.

Mineral Medium:
The mineral medium was prepared from four stock solutions using ultrapure grade water. The final composition was as follows:
Composition of the mineral medium:
Prepared from Compound Concentration mineral
medium [mg/L]
Stock solution 1 KH2PO4 85.0
K2HPO4 217.5
Na2HPO4 266.5
NH4Cl 5.00
Stock solution 2 CaCl2 *2 H2O 36.4
Stock solution 3 MgSO4*7 H2O 22.5
Stock solution 4 FeCl3 6*H2O 0.25
50 mL of stock solution 1 and 5 mL of stock solution 2 – 4 were given into 4000 mL deionised water.
For the abiotic control (treatment group 4) 500 mL of test medium were prepared separately, by adding 5 mL of stock solution 1 and 0.5 mL of stock solution 2 – 4.
All chemicals used were of analytical grade.

Test Medium:
The test medium (pH = 7.4 ± 0.2) was prepared by addition of activated sludge to the mineral medium and filled up to 5 L with deionised water. The concentration of activated sludge was adjusted to 20 mg/L.

Treatment Groups:
1. Test item group (test item and inoculum)
2. Procedure control group (reference item and inoculum)
3. Inoculum control group (inoculum)
4. Abiotic control group (test item and mercury chloride)
5. Toxicity control group (test item, reference item and inoculum)

For treatment groups 1 - 3 two replicates and for treatment groups of 4 and 5 one replicate was prepared.
The initial pH values were measured in the test item group after 0 and 28 days.
The oxygen uptake for each test vessel was measured continuously and recorded at 6 hour intervals.

Performance of the test:
For the test item replicates 1 L of test medium was prepared whereas for the procedure control replicates 100 mg sodium benzoate were weighed and added into 1 L of test medium. For the inoculum controls test medium was prepared. For the toxicity control 50 mg reference item were added to 500 mL test medium. The abiotic control was prepared by adding 5 mg HgCl2 to 500 mL mineral medium (no inoculum). Afterwards 250 mL were transferred into the respective test vessels by using volumetric flasks. Glass slides with 25 mg test item were given directly into the vessels where necessary. The preparation of the individual treatments is summarised in Table 2. Test vessels were put into the test chamber, and were allowed to acclimatise for about one hour at slightly opened manometer and test vessel lids. Afterwards lids were closed tightly and simultaneously.
The initial pH values were measured in the test item group after 0 and 28 days.
The oxygen uptake for each test vessel was measured continuously and recorded at 6 hour intervals.

Preparation of the test assays

Test item Reference item Inoculum control Abiotic control Toxicity control
100 mg/L 100 mg/L - 100 mg/L ref. item 100 mg/L test item
- - - 10 mg/L HgCl2 100 mg/L test item

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

50.9

Sampling time:

28 d

Details on results:

The O2 concentrations in the test vessels were measured at time intervals of 6 h from t = 0 days to t = 28 days. Due to digital data recording failure the O2 production on day 13 was corrupted for 7 hours and 39 minutes. Therefore all data rows were corrected by the mean delta of each data row. Therefore the mean delta was calculated using the deltas directly before and after the failure. These values were added to each data point obtained afterwards. All treatment groups but the abiotic control were corrected against the mean value of the inoculum controls. The results for the degradation test are given in the table below showing the calculated means indicating begin and end of 10 day-window. For test item replicates the 10% degradation levels where reached at day 2 and the 60% level was not reached. The reference item reached 10% degradation levels at day 1 and 60% levels at day 5. The overall degradation at the end of the 28 day test was 50.9% for the test item and 91.2% for the procedure control.
In the toxicity control, biodegradation amounted to 79% within 14 days of exposure. Thus, according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L because biodegradation in the toxicity control was > 25% within 14 days.
The abiotic control showed a negligible O2 demand of 2.3 mg/L

Mean results of the biodegradation experiment
10% O2 (calc) 10%-level passed [days] 60% O2 (calc) 60%-level passed [days] Overall degradation day 28 [%]
Test item 7.33 mg/L 2 44.0 mg/L - 50.9
Proc. control 16.7 mg/L 1 100.2 mg/L 5 91.2

Key result

Parameter:

COD

Value:

0.733 g O2/g test mat.

Results with reference substance:

The overall degradation at the end of the 28 day test was 91.2% for the procedure control containing the reference substance.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable, not fulfilling specific criteria

Conclusions:

Fast Pyrolysis Bio-oil biodegradation was determined to be 50.9 % (100 mg/L) in 28 days. Therefore, Fast Pyrolysis Bio-oil cannot be considered to be readily biodegradable under the conditions of this Manometric Respirometry Test.

Executive summary:

The ready biodegradability of Fast Pyrolysis Bio-oil was assessed with the Manometric Respirometry Test according to OECD Guideline 301 F. Fast Pyrolysis Bio-oil was tested at a nominal concentration of 100 mg/L.

The following biodegradation was determined at the end of the 28-d period:

* Fast Pyrolysis Bio-oil (100 mg/L): 50.9 %

* Sodium benzoate (100 mg/L): 91.2 %

Since the pass value of > 60% was not reached within the 10-day window Fast Pyrolysis Bio-oil cannot be considered to be readily biodegradable under the conditions of this Manometric Respirometry Test.

Fast Pyrolysis Bio-oil had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L.

Description of key information

Ready biodegradability of the test material was determined in a GLP compliant study according to OECD Guidelines for Testing Chemicals 301F (Ready biodegradability, Manometric Respirometry Test). As a result, the test material was found not to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Additional information

The ready biodegradability of the test material was studied at a loading rate of 100 mg/L. 50.9 % of the test material was degraded within 28 d. Since the pass value of > 60 % was not reached within the 10 -day window, Fast pyrolysis bio-oil cannot be considered readily biodegradable.