1-naphthol

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:

from June 16, 2016 to September 26,2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Test performed according to OECD 301B guideline and GLP.

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Version 1992. Ready Biodegradability: CO2 Evolution (Modified Sturm Test)

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Name: A017, 1-Naphthol
Batch Number: ADT1214003
CAS Number: 90-15-3
Storage Conditions: Ambient
Initial analysis : 27 May 2016 and purity : 98.9%
Re-analysis Date: 23 September 2016 and purity 99.2%
The purity is unchanged and remain 98.9%
Carbon Content: 83.30%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge : collected from the Easton Wastewater Treatment Facility, Easton, Maryland on July 07, 2016. The Easton facility treats predominantly residential wastes
- Storage length : up to 3 days
- Preparation of inoculum for exposure : the sludge was sieved using a 2-mm screen, adjusted to approximately 1,000 mg total suspended solids/L with mineral media and then aerated at test temperature until use
- Concentration of sludge: A total suspended solids measurement and standard plate count were performed on the inoculum on the day of use in the test. Plates were incubated at 20 ± 3ºC for approximately 48 hours. Standard plate count = 2.2 x 10E+4 CFU/mL and TSS measurement = 893 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium:
2470 mL of NANOpure water
3 mL calcium chloride solution (2.75%)
3 mL of ferric chloride solution (0.025%)
3 mL of magnesium sulfate solution (2.25%)
30 mL of phosphate buffer (pH 7.4)
A volume of activated sludge inoculum to achieve a final TSS concentration of ≤30 mg/L

- Test temperature: 20 ± 3ºC
- pH: 7.6
- pH adjusted: no
- CEC (meq/100 g): not reported
- Aeration of dilution water: All chambers were aerated with CO2-free air for approximately 24 hours at a rate of approximately 55 mL per minute to purge the systems of CO2. Magnetic stirrers will be employed to mix the contents of the chambers. The stirrers will be cycled on and off every 15 min. to prevent the transfer of heat.
- Suspended solids concentration: Final concentration in the test chanber ≤30 mg/L
- Continuous darkness: not reported

TEST SYSTEM
- Culturing apparatus: Test Chamber of 4 liter. A final volume within all chambers was brought up to 3000 mL by the addition of NANO pure water.
- Number of culture flasks/concentration: 3 per concentration
- Method used to create aerobic conditions: Biodegradation was started by bubbling CO2-free air through each of the test chambers at a rate of approximately 55 mL per minute.

- Measuring equipment:
- Details of trap for CO2 : After the aeration period, the flow of CO2-free air was stopped, and three CO2 traps, each containing approximately 100 mL of 0.5 M KOH, were connected to the exit air lines of each chamber. The CO2 trap nearest the test chamber was removed and analyzed for inorganic carbon. The two remaining traps were placed one position closer to the test chamber and a new trap was placed on the end of the series.

SAMPLING
- Sampling frequency: On days 3, 6, 9, 13, 16, 20, 23 and 27.
- Sampling method: The CO2 produced from the degradation of organic carbon sources within the test chamber was trapped as K2CO3 in the KOH solution and the amount of inorganic carbon in the trapping solution was measured using a Shimadzu Model TOC-VCSH carbon analyzer.
Test termination : On the 28th day of the test, an aliquot of the contents of each test chamber was removed and the pH determined. The contents of all chambers were then acidified by the addition of 1 mL of concentrated hydrochloric acid to drive off inorganic carbonate. All chambers were aerated overnight and then a sample from each test chamber was removed for dissolved organic carbon (DOC) analysis and the trapping solutions closest to the test chambers were analyzed for inorganic carbon.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicats
- Abiotic sterile control: : not performed
- Toxicity control: 1 replicat
- Positive control (sodium benzoate) : 3 replicats

Reference substance:

benzoic acid, sodium salt

Remarks:

A nominal concentration of 10 mg C/L was added in the appropriate chambers (reference and toxicity controls)

Key result

Parameter:

% degradation (CO2 evolution)

Value:

77.8

St. dev.:

1.7

Sampling time:

29 d

Details on results:

The blank control chambers evolved an average of 41.5 mg CO2 over the test period. It did not exceed the 40 mg/L (120 mg total) value considered the acceptable limit for CO2 evolution tests.
The difference of extremes of replicate values of the removal of the test chemical at the end of the test is less than 20% (79.6%; 77.8% and 76.20%).
The toxicity control achieved > 25% degradation by Day 14 and may be considered non-inhibitory at the concentration tested in this study.

The final mean percent biodegradation for A017 was 77.8%. A017 may be considered as readily biodegradable since the pass level of 60% biodegradation was achieved within 10 days of achieving 10% biodegradation.

Results with reference substance:

The reference substance, sodium benzoate, shows a biodegradation of 94.3%. An average percent biodegradation of greater than 60% was achieved by Day 6, thereby fulfilling the criteria for a valid test by reaching the pass level by Day 14.

Percentage of biodegradation- A017
Days	Replicate1	Replicate2	Replicate3	mean biodeg (%)	+/- SD (%)	CV (%)
3	0.20	-1.20	-1.00	-0.67	0.76	-113.58
6	45.20	28.10	15.40	29.57	14.95	50.58
9	61.70	50.80	46.30	52.93	7.92	14.96
13	71.90	65.70	61.60	66.40	5.19	7.81
16	76.60	71.00	67.20	71.60	4.73	6.60
20	78.30	73.60	71.60	74.50	3.44	4.62
23	79.00	74.60	73.70	75.77	2.84	3.74
27	79.60	76.40	75.70	77.23	2.08	2.69
29	79.60	77.80	76.20	77.87	1.70	2.18

 

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The substance 1-Naphtol is biodegraded to a level of 77.8% within the 10 day-window in a ready biodegradation test OCDE 301B. A017 is considered as readily biodegradable

Executive summary:

The ready biodegradability of 1-Naphthol (A017), was determined by the Carbon Dioxide Evolution Test Method (OECD Guideline 301B) under GLP. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2 (TCO2) that could have been produced if complete biodegradation of the test substance occurred. There were 3 replicates of test chamber that consist of the blank control group (to measure the background CO2 production by the inoculum), the reference group containing 10 mg C/L of sodium benzoate known to be biodegradable, the treatment group containing 10 mg C/L of A017, and a single toxicity control containing the reference and the tested substances each at 10 mg C/L.

The results indicated that the activated sludge inoculum was active, degrading the reference substance at an average of 94.3% and that the test substance was not inhibitory to the inoculum at the concentration tested, as the toxicity control exceeded 25% degradation by Day 14 of the study. All the validity criteria are fulfilled.

The average percentage of biodegradation of A017 was 77.8%. 1 -Naphtol is considered as readily biodegradable since the pass level of 60% was achieved within 10 day-window.

Description of key information

The substance 1-Naphtol is biodegraded to a level of 77.8% within the 10 day-window in a ready biodegradation test OCDE 301B. A017 is considered as readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradability of 1-Naphthol (A017), was determined by the Carbon Dioxide Evolution Test Method (OECD Guideline 301B) under GLP. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2 (TCO2) that could have been produced if complete biodegradation of the test substance occurred. There were 3 replicate of test chamber that consist of the blank control group (to measure the background CO2 production by the inoculum), the reference group containing 10 mg C/L of sodium benzoate known to be biodegradable, the treatment group containing 10 mg C/L of A017, and a single toxicity control containing the reference and the tested substances, each at 10 mg C/L.

The results indicated that the activated sludge inoculum was active, degrading the reference substance at an average of 94.3% and that the test substance was not inhibitory to the inoculum at the concentration tested, as the toxicity control exceeded 25% degradation by Day 14. All the validity criteria are fulfilled.

The average percentage of biodegradation of A017 was 77.8%. 1 -Naphtol is considered as readily biodegradable since the pass level of 60% was achieved within 10 day-window.