p-phenylbenzaldehyde

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:

1998-12-08 to 1999-02-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Severn Trent Water Pic sewage treatment plant at Belper, Derbyshire, UK

- Pretreatment: The sample of activated sewage sludge was maintained on continuous aeration upon receipt. A sample of the activated sewage sludge was washed three times by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. A sub-sample of the washed sewage sludge was then removed and the suspended solids concentration determined.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

ThCO2

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Prepared acoording to OECD guideline
- Test temperature: 21 °C
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 L glass culture vessels
- Number of bottles containing the test item and inoculum: 2
- Number of bottles containing procedure control: 1
- Number of bottles containing inoculum control: 2
- Number of bottles containing toxicity control: 1
- Number of bottles containing abiotic control: 1
- Measuring equipment: Ionics 1555B TOC analyser
- Test performed in closed: yes

SAMPLING
- Sampling frequency:
The samples taken on days 0, 1, 2, 3, 6, 8, 10, 14, 16, 22, 27, 28 and 29 were analysed for CO2 immediately. The samples taken on days 12, 18, 20 and 24 were stored deep frozen at -20 °C. However, these samples were not analysed for CO2 as the results obtained from previous and subsequent analyses showed that degradation of the test material had met the 10 day window validation criterion given in the OECD Guidelines and therefore additional analyses were considered to be unnecessary.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes
- Test suspension: yes

Reference substance:

benzoic acid, sodium salt

Test performance:

The following test solutions were prepared and inoculated in 5 litre glass culture vessels each containing 3 litres of solution:
a) A control, in duplicate, consisting of inoculated culture medium.
b) The standard material (sodium benzoate), in duplicate, in inoculated culture medium to give a final test concentration of 10 mg carbon/L.
c) The test material, in duplicate, in inoculated culture medium to give a final test concentration of 10 mg carbon/L.
d) The test material plus the standard material in inoculated culture medium to give a final concentration of 20 mg carbon/L to act as toxicity control (one vessel only).
Each test vessel was inoculated with the prepared inocurum at a final concentration of 30 mg suspended solids (ss)/L. The study was carried out in a temperature controlled room at 21 °C, in darkness.
Approximately 24 hours prior to addition of the test and standard materials the vessels were filled with 2400 mL of culture medium and 30 mL of inoculum and aerated overnight. On day 0 the test and standard materials were added and the volume in all the vessels adjusted to 3 litres by the addition of culture medium.
The culture vessels were sealed and CO2-free air bubbled through the solution at a rate of approximately 40 mL/minute and stirred continuously by magnetic stirrer.
The CO2-free air was produced by passing compressed air through a glass column containing self-indicating (Carbosorb®) granules.
The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified de-gassed water.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

61

Sampling time:

28 d

Details on results:

The test material attained 61 % degradation after 28 days and satisfied the 10-day window validation criterion.

Results with reference substance:

Sodium benzoate attained 85 % degradation after 28 days thereby confirming the suitability of the inoculum and test conditions. The increase in inorganic carbon in the first absorber vessels on day 29 resulted in an increase in the percentage degradation value for the standard material from 85 % on day 28 to 89 % on day 29.

Table 1: Percentage Biodegradation Values

Day	% Degradation Sodium Benzoate	% Degradation p-phenylbenzaldehyde	% Degradation p-phenylbenzaldehyde plus sodium benzoate Toxicity control
0	0	0	0
1	21	3	11
2	38	2	18
3	39	2	29
6	66	1	45
8	80	38	65
10	79	43	70
14	81	50	72
16	81	61	75
22	84	58	70
27	82	61	73
28	85	61	72
29*	89	64	75

*Day 29 values corrected to include any carry-over of CO₂ detected in absorber 2

 

Table 2: Total and inorganic Carbon Values in the Culture Vessels on Day 0

Test Vessel	Total Carbon (mg/L)	Inorganic Carbon (mg/L)	% Inorganic Carbon
Sodium benzoate 10 mg C/L R1	14.04	2.39	17
Sodium benzoate 10 mg C/L R2	13.25	2.42	18
p-phenylbenzaldehyde 10 mg C/L R1	13.11	1.72	13
p-phenylbenzaldehyde 10 mg C/L R2	13.23	1.95	15
p-phenylbenzaldehyde plus Sodium benzoate Toxicity Control 10 mg C/L R1	23.13	1.43	6

R₁ – R₂ – Replicates

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test material attained 61 % degradation after 28 days and satisfied the 10-day window validation criterion. The test material can therefore be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

Executive summary:

A study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the OECD Guidelines 301B, Method C.4-C and US EPA Ecological Effects Test Guidelines OPPTS 835.3110 Paragraph (M).

The test material was exposed to activated sewage sludge micro-organisms at a concentration of 10 mg C/L with culture medium in sealed culture vessels in the dark at 21 °C for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

The total CO₂ evolution in the control vessels on day 28 was 29 mg/L(≡ 87 mg/3L) and therefore satisfied the validation criterion given in the OECD Guidelines.

The results of the inorganic carbon analysis of samples from the first absorber vessels on day 29 showed an increase in all replicate vessels. These increases are considered to be due to CO₂ present in solution being driven off by the addition of hydrochloric acid on day 28 and resulted in an increase in the percentage degradation value for the test material from 61 % on day 28 to 64 % on day 29.

Inorganic carbon analysis of the samples from the second absorber vessels on day 29 confirmed that no significant carry-over of CO₂ into the second absorber vessels occurred.

The TC/IC ratio of the test material dispersions was in excess of the recommended level of 5 % given in the Test Guidelines. This is considered to be due to the low TC concentration in the test medium and hence the IC contribution is relatively large. This is not considered to affect the integrity of the study or the results obtained given that the CO₂ evolution in the control vessels satisfied the validation criteria.

The toxicity control attained 72 % degradation after 28 days thereby confirming that the test material was not toxic to the sewage treatment micro-organisms used in the study. The increase in inorganic carbon in the first absorber vessels on day 29 resulted in an increase in the percentage degradation value for the toxicity control from 72 % on day 28 to 75 % on day 29.

Sodium benzoate attained 85 % degradation after 28 days thereby confirming the suitability of the inoculum and test conditions. The increase in inorganic carbon in the first absorber vessels on day 29 resulted in an increase in the percentage degradation value for the standard material from 85 % on day 28 to 89 % on day 29.

The test material attained 61 % degradation after 28 days and satisfied the 10-day window validation criterion. The test material can therefore be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

Description of key information

The test material attained 61 % degradation after 28 days and satisfied the 10-day window validation criterion. The test material can therefore be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

 

The biodegradation of the test item was examined via Oxygen demand (OD) and the test item was found to be not readily biodegradable with a biodegradation rate of 6.7 % (via OD). This study is disregarded because it was not performed according to guideline and GLP.

 

OECD 301B

A study was performed to assess the ready biodegradability of the test material in an aerobic aqueous media. The method followed that described in the OECD Guidelines 301B, Method C.4-C and US EPA Ecological Effects Test Guidelines OPPTS 835.3110 Paragraph (M).

The test material was exposed to activated sewage sludge micro-organisms at a concentration of 10 mg C/L with culture medium in sealed culture vessels in the dark at 21 °C for 28 days. The degradation of the test material was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the standard material, sodium benzoate, together with a toxicity control were used for validation purposes.

The test material attained 61 % degradation after 28 days and satisfied the 10-day window validation criterion. The test material can therefore be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.