Hexadecan-1-ol

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Remarks:

Good quality study but not conducted to GLP. Published paper based on a more complete unpublished study report.

Qualifier:

according to guideline

Guideline:

OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units)

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Initial conc.:

4 mg/L

Based on:

test mat.

Details on study design:

Laboratory continuous activated sludge study.

Concentration: 4 mg/L of TS
Temperature: 20ºC
Hydraulic residence time (HRT) 6 h
Sludge retention time (SRT) 10 d

The feed to the sludge unit was of sterile synthetic sewage and AE concentrate and non-sterile tap water.

19 d acclimation was used, followed by 10 days of evaluation.

At the start the unit was seeded with sewage treatment plant (STP) activated sludge.

The unit was sampled several times per week, and the samples were analysed immediately.

Test performance:

Analytical recovery of the alcohols was high.

The results showed that the CAS unit was running in a similar way to a full scale STP.

% Degr.:

99.5

Parameter:

test mat. analysis

Sampling time:

30 d

Details on results:

Results are corrected for control values.

Alcohol Conc. in Conc. in % removal
effluent ng/L sludge µg/g
C12 18 0.6 98.6
C13 21 0.7 99.5
C14 5.5 0 99.6
C15 2.9 1.1 99.8
C16 1.6 0.01 99.5
C18 58 0.7 99.1
Total 130 2 99.4

Total elimination of alcohols, correcting for control: 97.4% of input
Total alcohols in waste sludge solids 2.0% of input
Total alcohols in suspended solids 0% of input
Total alcohols dissolved in effluent 0.7% of input

This shows that most of that which does not degrade (itself a small amount) is in the solids.

Conclusions:

A very high degree of removal of C12-18 alcohols from a test substance constituting alcohols as part of a mixed alcohol ethoxylate test substance was demonstrated in a 30-day test using a continuous activated sludge simulation methodology. The findings are reliable as part of a weight of evidence.

Reference 2

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2005-03-30 to 2005-06-08

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The study was conducted according to a test protocol that is comparable to the appropriate OECD test guideline. It was not compliant with GLP.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD 314B. Deviations, reliability, and validity evaluated against current OECD 314B (Oct. 3, 2008)

Deviations:

no

Principles of method if other than guideline:

Radiolabelled test material was dosed to freshly collected activated sludge in an open test system. Periodically subsamples were collected, lyophilised and extracted. The disappearance of parent and progression of metabolite formation and decay were monitored over time by thin layer chromatography with radioactivity detection. Production of CO2 was determined by comparing total radioactivity in a bioactive treatment compared to that in an abiotic control using liquid scintillation counting (LSC).

GLP compliance:

no

Remarks:

study conducted before 2008

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on source and properties of surface water:

Not applicable

Details on source and properties of sediment:

Not applicable

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge mixed liquor was obtained from Fairfield Wastewater Treatment Plant (Fairfield, OH), which receives predominantly domestic wastewater.

- Storage length: None (radiolabeled test material was dosed to freshly collected activated sludge)

- Preparation of inoculum for exposure: Not reported

- Concentration of sludge: TSS of sludge at the time of collection is not provided in the report. However, the solids level of the mixed liquor suspended solids was adjusted to 2500 mg/L before use.

- Initial cell/biomass concentration: Not reported

Duration of test (contact time):

48 h

Initial conc.:

10.7 µg/L

Parameter followed for biodegradation estimation:

CO2 evolution

test mat. analysis

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: Approx. 1 L

- Composition of medium: Each 2 L test flask contained: 1 L activated sludge; 0.05 µM of Hexadecanol.

- Test temperature: The test flasks were incubated at 20±2°C and gently mixed on shaker table.

- pH: 7

- Aeration of dilution water: No

- Suspended solids concentration: 2500 mg/L of TSS

- Continuous darkness: Not reported

TEST SYSTEM
- Culturing apparatus: 2 L flasks

- Number of culture flasks/concentration: One

- Method used to create aerobic conditions: Test was conducted in open test system.

- Measuring equipment: Mineralization to 14CO2 was determined indirectly by measuring the difference in total radioactivity between samples from the biotic and abiotic treatments.

- Test performed in open system: Yes

SAMPLING
- Sampling frequency: At 0.02, 0.08, 0.25, 0.5, 1, 1.5, 2, 3, 4, 5.5, 24, 48, and 144 h.

- Sampling method: At each sampling, each sludge mixture was mixed thoroughly and sampled as follows:

a) For determination of mineralization: Triplicate 1 mL samples of the mixed sludge were removed and and placed into 20 mL glass scintillation vials containing 1 mL of 0.5% HCI. acidified samples were incubated overnight.

b) For analysis of parent, metabolite and radioactivity associated with solids: 25 mL of sludge was collected from each treatment and transferred to a 35 mL screwtop centrifuge tube and immediately frozen in a dry ice acetone bath. The frozen samples were stored at -80°C until lyophilization on a Virtis bench-top model 3.3L freeze dryer.Analysis of sample is discussed in ‘Details on analytical method’ section.

- Sample storage before analysis: Not specified.

CONTROL AND BLANK SYSTEM
- Inoculum blank: No

- Abiotic sterile control: Yes (Sludge was autoclaved and amended with mercuric chloride (1g/L) to serve as an abiotic control)

- Toxicity control: No

STATISTICAL METHODS: For kinetic analysis, the data describing the disappearance of parent were fitted to various equations using Jandel TableCurve 2D software, Version 4.0. Based on statistical considerations and the visual quality of the fit, the two-compartment first order decay model was used to fit all data.

Reference substance:

not required

Test performance:

No data

Compartment:

other: water, material (mass) balance

% Recovery:

99.5

Key result

% Degr.:

66.3

Parameter:

CO2 evolution

Remarks:

(Mineralization)

Sampling time:

48 h

Key result

% Degr.:

17.1

Parameter:

other: % of radioactivity associated with solids

Sampling time:

48 h

Key result

% Degr.:

2.6

Parameter:

other: % of radioactivity as parent

Sampling time:

48 h

Key result

% Degr.:

13.6

Parameter:

other: % of radioactivity as metabolite

Sampling time:

48 h

Key result

Compartment:

activated sludge

DT50:

>= 0.4 - <= 97 min

Type:

(pseudo-)first order (= half-life)

Temp.:

20 °C

Remarks on result:

other: half-life for removal of parent. The shorter half-life (pool 1) is the most relevant for predicting removal of a chemical in an activated sludge system. This rate describes the biodegradation of the fraction in solution.

Other kinetic parameters:

first order rate constant

Transformation products:

yes

No.:

#1

No.:

#2

Details on transformation products:

- Formation and decline of each transformation product during test: Hexadecanoic acid reached a maximum level of 15.3% after 2 h, while polar metabolites reached their maximum level of 7.3% after 1.5 h. Concurrent with the loss of parent, there was the instantaneous appearance of fatty acids and polar metabolites, which peaked and subsequently declined.

- Pathways for transformation: Hexadecanol degradation involved two pathways: oxidation of the alcohol to a fatty acid, which was beta oxidized to form carbon dioxide, and omega; oxidation of the methyl group to yield dioic acids, which undergo beta oxidation from either direction

- Other: The majority of the activity in abiotic control remained as parent, 12.3% of radioactivity was in the form of transformation products, which had chromatographic mobility similar to the two major metabolites observed in the biotic treatments.

Evaporation of parent compound:

no

Volatile metabolites:

no

Residues:

yes

Details on results:

TEST CONDITIONS
- Aerobicity, moisture, temperature and other experimental conditions maintained throughout the study: Yes

TRANSFORMATION PRODUCTS: Please refer to the above section 'Details on transformation products'.

TOTAL UNIDENTIFIED RADIOACTIVITY (RANGE) OF APPLIED AMOUNT: Not reported

EXTRACTABLE RESIDUES
- % of applied amount at Day 0: 74.95% (parent and metabolite; sample time was 0.02 h)

- % of applied amount at end of study period: 16.15% (parent and metabolite; sample time was 48 h)

NON-EXTRACTABLE RESIDUES
- % of applied amount at Day 0: 12.09% in active flask (sample time was 0.02 h)

- % of applied amount at end of study period: 17.12% in active flask (sample time was 48h)

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: 66.3% in bioactive test flask (sample time was 48 h). CO2 evolution was not analyzed for abiotic flask as majority of the radioactivity in the abiotic control was recovered primarily as intact parent. For details, please refer to ‘table 1’ and 'table 2'in the ‘Any other information on results incl. tables’ section.

VOLATILIZATION: No volatilization of test material was observed as the TLC analysis of the abiotic control revealed that the parent test material remained intact throughout the experiment.

Continuous activated sludge (CAS) study of Hexadecanol (study # 45535)

Table 1: Biotic flask

Sampling time (h)	Parent and less polar metabolite* (%)	Water extracted (polar metabolite)	Associated with solids (%)	CO2 (%)	Mass balance
0.02	69.32	5.63	12.09	17.23	104.27
0.08	66.04	6.13	12.38	21.37	105.92
0.25	56.6	5.41	14.77	27.12	103.9
0.5	55.52	5.6	19.11	22.12	102.35
1	53.48	5.84	16.49	24.2	100.01
1.5	44.84	7.33	19.84	30.28	102.30
2	37.08	6.19	18.79	34.67	96.72
3	31.52	6.37	20.93	52.02	110.84
4	26.76	6.51	22.59	44.17	100.02
5.5	14.12	3.84	15.3	NA	NA
24	10.6	3.09	23.1	54.92	91.71
48	14.04	2.11	17.12	66.25	99.51

* Extracted using methanol as solvent

 

 

Table 2: Abiotic flask

Sampling time (h)	Parent (%)	Metabolite (%)	Water extracted	Associated with solids (%)	CO2 (%)	Mass balance
48	83	11.8	0.5	1.2	NA	96.5

 

 

 

Table 3: Predicted removal of parent Hexadecanol from activated sludge as a function of the concentration of effluent solids

	% Removed as a Function of Effluent Solids
Kd (L/kg)	0 mg/L	5 mg/L	20 mg/L
8486	99.84	99.82	99.76

Validity criteria fulfilled:

yes

Conclusions:

A reliable study conducted according to to generally accepted scientific principles determined the substance to achieve 66.3% mineralization, 17.1% was non-extractable (solids), 13.6% was metabolite, and 2.6% remained as parent after 48 hours. The rate constants for primary biodegradation and mineralisation in activated sludge were 103.4 and 1.8 h-1, respectively.

Executive summary:

A simulation of the biodegradation of Hexadecanol in activated sludge was conducted under aerobic conditions in accordance with the OECD 314B guideline. A solution of radiolabeled Hexadecanol (1-14C) was tested at 10.7 µg/L.  The inoculum was activated sludge obtained from Fairfield Wastewater Treatment Plant (Fairfield, OH), which receives predominantly domestic wastewater.

After 48 h, 66.3% was mineralized, 17.1% was non-extractable (solids), 13.6% was metabolite, and 2.6% remained as parent. The rate constants for biodegradation of Hexadecanol in activated sludge were:

Primary biodegradation: 103.4 h^-1

Mineralization: 1.8 h^-1

This biodegradation simulation test satisfied the guideline requirements for the OECD 314 B simulation tests to assess the biodegradability of chemicals discharged in wastewater.

Reference 3

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1993-06-08 to 1993-07-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was well documented, equivalent to an appropriate test guideline and in compliance with GLP.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD 314D. Deviations, reliability, and validity evaluated against current OECD 314D (Oct. 3, 2008)

Deviations:

no

Principles of method if other than guideline:

Radiolabelled test material was dosed to freshly collected river water and inoculum. Samples collected periodically were assayed for 14C activity by Liquid Scintillation Counting (LSC).

GLP compliance:

yes

Remarks:

EPA GLP (40 CFR, Part 792)

Radiolabelling:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: River water supplemented with domestic activated sludge

Details on source and properties of surface water:

- Details on collection: River water was collected on 7 June 1993 from the East Branch of the Brandywine Creek in Downingtown, Pennsylvania. The water was collected just below the surface using plastic containers.

- Storage conditions: River water was stored under refrigeration until used.

- Storage length: 1 d

- Temperature (°C) at time of collection: Not reported

- pH at time of collection: 7.9

- Electrical conductivity: Not reported

- Total Organic Carbon: 3.5 mg/L

- Total Suspended Solids: 3 mg/L

- Hardness: 101 mg/L

- Biomass: 1.3 x 10(4) CFU/mL (river water); 8.4 x 10(3) CFU/mL (river water supplemented with inoculum)

Details on source and properties of sediment:

Not applicable

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge collected from the Downingtown Regional Water Pollution Control Center, Downingtown, Pennsylvania

- Storage length and conditions: The sludge was held overnight with aeration

- Storage length: Overnight

- Preparation of inoculum for exposure: The sludge was screened to remove large clumps and a TSS level was determined. Based on this reading the sludge was added to two semi-continuous activated sludge units (SCAS) at a target solids level of 2,500 mg/L. The sludge was diluted to this concentration with tap water. Approx. 300 mL of mixed liquor was collected from each of the duplicate SCAS units, composited and homogenized at medium speed in a blender for 2 min. The homogenized sample was poured into a beaker and allowed to settle for 30 min. The supernatant was decanted and added to the flasks at a concentration of 0.1% v/v.

- Concentration of sludge: The sludge was adjusted to a target total suspended solids level of 2500 mg/L

Duration of test (contact time):

31 d

Initial conc.:

100 µg/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Volume of test solution/treatment: Approx. 1L

- Composition of medium: Each 2 L test flask contained:1 L river water; 1 mL activated sludge; 241 µL dosing solution; - Test temperature: 20.6 - 22.5 °C

- pH: Not reported

- Aeration of dilution water: The flasks were placed on a rotary platform shaker and aerated continuously with a CO2 free air source.

- Suspended solids concentration: 2500 mg/L

- Continuous darkness: Not reported

TEST SYSTEM
- Culturing apparatus: 2 L Erlenmeyer glass flasks

- Number of culture flasks/concentration: Two per concentration

- Method used to create aerobic conditions: The flasks were placed on a rotary platform shaker (100 to 150 rpm) and aerated continuously with a CO2 free air source. Air was purged through the scrubbing train at a constant rate which is adequate to provide 1-2 bubbles/second in the alkali traps. The CO2 scrubbing apparatus consisted of: (a) One empty 1 L plastic bottle, to prevent backflow; (b) Five 1 L plastic bottles containing 700 mL 10 N NaOH and (c) One empty 1 L plastic bottle to prevent overflow of alkali into the test containers connected in series with Tygon tubing to a pressurized air source (approx. 10-15 psi).

- Test performed in closed vessels: Yes

- Details of trap for CO2 and volatile organics if used: Glass bottles approx. 4 oz size containing 100 mL of 1.5 N KOH.

- Other: The study was terminated on Day 31 by adding 1 mL concentrated HCl to the flasks. Following an incubation of 3 d, duplicate 10 mL water samples were withdrawn from each flask and counted in Triton-X cocktail. Duplicate 1 mL samples from all three alkali traps were collected and counted in 20 mL Cab-O-Sil cocktail.

SAMPLING
- Sampling frequency: On Days 1, 3, 5, 7, 10, 14, 21, 28 and 31

- Sampling method: The first 14CO2 alkali trap in the individual trains was removed and a 1mL aliquot was counted in 20 mL of Cab-O-Sil. The remaining traps were moved one slot closer to the test flask and a new trap was added to the third slot. At the same time 10 mL water samples are withdrawn by syringe from each test flask and filtered through 0.2 µm filters. The filters were washed with 5 mL IPA/water, air dried, and counted in 20 mL of 3A cocktail to quantitate radioactivity in the biomass. The filtrate was treated as described in "Details on analytical methods" above.

- Sample storage before analysis: Not specified

CONTROL AND BLANK SYSTEM
- Inoculum blank: No

- Abiotic sterile control: No

- Toxicity control: No

STATISTICAL METHODS: Percent 14CO2 production vs time was analysed by the following empirical model: 14CO2 = a (1 - e(-k(t-c)))where,a = Extent of 14CO2 production (%)k = First order rate constant (day-1)t = Time of incubation (days)c = Lag period, if any (days). The constants a and k along with 95 % confidence intervals were generated for each treatment

Reference substance:

not required

Test performance:

No data

Compartment:

other: water, material (mass) balance

% Recovery:

100

Remarks on result:

other: reported as 105% in source.

% Degr.:

97.5

Parameter:

CO2 evolution

Sampling time:

31 d

Remarks on result:

other: Test replicate 1

% Degr.:

92.4

Parameter:

CO2 evolution

Sampling time:

31 d

Remarks on result:

other: Test replicate 2

% Degr.:

95

Parameter:

CO2 evolution

Sampling time:

31 d

Remarks on result:

other: Average of test replicates 1 and 2

Other kinetic parameters:

first order rate constant

Transformation products:

not measured

Evaporation of parent compound:

not measured

Volatile metabolites:

not measured

Residues:

yes

Details on results:

TEST CONDITIONS
- Aerobicity , moisture, temperature and other experimental conditions maintained throughout the study: Yes

MAJOR TRANSFORMATION PRODUCTS: Not determined in the study.

MINOR TRANSFORMATION PRODUCTS: Not determined in the study.

MINERALISATION
- % of applied radioactivity present as CO2 at end of study: 97.5 and 92.4% for Flask 1 and 2 respectively. For details see ‘Table1’ and 'Table 2' below in the ‘Any other information on results incl. tables’ section.

Results with reference substance:

Not applicable

14 CO2 production of Cetyl Alcoholin river water (Study # 35425)

Day	Indirect % T 14CO2	Direct % T 14CO2	Biomass % 14C	Solution % 14C	Mass balance
1	66	47	23.9	10.1	81
3	68.7	56.4	20.2	11.1	87.7
5	68	65.3	22.7	9.3	97.3
7	73.9	73.8	19.1	7	99.9
10	74.7	80.4	19	6.3	105.7
14	80.5	80.9	13.3	6.2	100.4
21	85.8	93	9.8	4.5	107.3
28	89.9	96	7	3.1	106.1
31	91.7	97.5	6	2.2	105.7

 

 

Table 2: Flask 2

Day	Indirect % T 14CO2	Direct % T 14CO2	Biomass % 14C	Solution % 14C	Mass balance
1	60.2	40.8	28.9	10.9	80.6
3	69.6	53.9	19.9	10.5	84.3
5	66.2	63.4	23.4	10.4	97.2
7	71.8	69.9	18.5	9.7	98.1
10	73.1	78.8	19	7.8	105.6
14	81.8	81.2	11	7.2	99.4
21	87.9	86.1	7.3	4.8	98.2
28	91.6	91.5	5.4	3	99.9
31	93.6	92.4	4.3	2.1	98.8

Validity criteria fulfilled:

yes

Conclusions:

A reliable study conducted according to generally accepted scientific principles determined the substance to achieved a percentage degradation of 95.0% (CO2 produced) over 31 days, and rate constant for mineralization in surface water was 0.34 day-1. Results are the average of 2 test flasks.

Executive summary:

A simulation of the mineralization of Cetyl Alcohol in surface water amended with activated sludge was conducted under aerobic conditions in accordance with the OECD 314D guideline. Cetyl Alcohol was tested at 100 µg active/L. The river water was collected from East Branch of the Brandywine Creek in Downingtown, Pennsylvania and the activated sludge inoculum was collected from Downington Regional Water Pollution Control Center. The test was run in duplicate.

After 31 d, the cumulative percent of theoretical 14CO2 produced was 95% (mean of flasks 1 and 2 having values 97.5 and 92.4 respectively).

The rate constant for biodegradation of Cetyl Alcohol in surface water was 0.34 day^-1(mean of flasks 1 and 2 having values 0.35 and 0.33 day^-1respectively).

This biodegradation simulation test satisfied the guideline requirements for the OECD 314D simulation tests to assess the biodegradability of chemicals discharged in wastewater.

Description of key information

Simulation test: ISO 11733: 1995 - 98% mineralisation (last 30 days of test) and OECD 314D: 1993 - 95% CO2 evolution.

Primary degradation is rapid with evidence of rates in the range 0.7 - 17 d- ¹ in the dissolved phase.

Key value for chemical safety assessment

Half-life in freshwater:

2.1 d

at the temperature of:

12 °C

Half-life in freshwater sediment:

0.6 d

at the temperature of:

12 °C

Additional information

In accordance with Column 2 of REACH Annex IX, the simulation test on ultimate degradation in surface water and the sediment simulation test (required in Sections 9.2.1.2 and 9.2.1.4 respectively) do not need to be conducted as the substance is readily biodegradable. Identification of degradation products (required in Section 9.2.3) is also not necessary because extensive mineralisation has been demonstrated.

Measured data are available for Hexadecan-1-ol. Radiolabelled C16 alcohol was found to biodegrade at 66.3% CO2 evolution over 48 hours in a batch-mode activated sludge die-away system study conducted according to or similar to OECD 314B (Federle 2005), and on a similar chain length alcohol (C14) as described in the discussion below. This biodegradation simulation test satisfied the guideline requirements for the OECD 314 B simulation tests to assess the biodegradability of chemicals discharged in wastewater. The rate constants for primary biodegradation and mineralization of hexadecanol in activated sludge were 103.4 h^-1and 1.8 h^-1, respectively. This study was not conducted according to GLP and has been assigned reliability 2.

Another reliable study conducted on the test substance reports a degradation of 95% (CO2 evolution) over a 31 days period (Federle 1993). This study was done according to or similar to OECD 314D and GLP requirements using a river water supplemented with domestic activated sludge as test system. It was assigned reliability 1.

It is appropriate to read across the C15 CAS result to similar chain lengths, but without extrapolating too far. It is suggested that C12 to C18 would be a realistic read-across range, on grounds of similar degradation and adsorption. Radiolabelled pentadecanol (branched with an average of 1.4 branches) was studied in a model continuous activated sludge (CAS) plant (Battersby N J, Sherren A J, Bumpus R N, 1999).

The CAS plant was fed daily with fresh domestic sewage, and the input concentration of pentadecanol was 1 mg/l, dispersed with a surfactant. The study duration was 53 days, allowing for a stabilisation period followed by a measurement period. Over the last 30 days of the study the substance was 98% mineralised, with 0.05% pentadecanol remaining in the effluent, and 0.4% of the radioactivity adsorbed to the sludge. The overall removal from influent was >99.9%, and removal from the total system was 99.5%. Of the remaining (non-mineralised) radioactivity there was evidence of more polar metabolites being formed as well as lipids derived from the alcohol. The study is Klimisch 1. GLP applies to a study conducted in accordance with an ISO method (ISO 11733:1995) comparable to the OECD 303 method (EU C.10).

Therefore the two higher results from the higher reliable studies are used as Weight of Evidence.

Discussion of trends in the Category of C6 -24 linear and essentially-linear aliphatic alcohols

Sediment simulation testing

The degradation of C14 linear alcohol in sediments was determined in two studies conducted in accordance with OECD 314 test method and using radiolabelled (¹⁴C) test substance. After 92 days, 76.5% mineralisation to CO₂was obtained using sediment from Ohio River near Cincinnati, Ohio area (Federle T Wand Itrich N R, 2010a). After 149 days, 83.6% mineralisation to CO₂was obtained using Lytle Creek sediments from Wilmington, Ohio (Federle T W and Itrich N R, 2010b).

The degradation of C18 linear alcohol in sediments was determined in a similar study, conducted in accordance with OECD 314 test method and using radiolabelled (¹⁴C) test substance (Itrich, 2010). After 60 days, 61.1% mineralisation to CO₂ was obtained using sediment from Ohio River, and 71.6% mineralisation to CO₂ after 60 days was obtained using Great Miami River sediments.

The radiochemical analytical results for sediment-associated and aqueous alcohols in these three sediment degradation studies indicatedthat there are two pools of substance, understood to represent the strength of adsorption of the alcohol to sediment particles, which degrade at different rates.

Activated sludge simulation testing

A simulation of the biodegradation of dodecanol in an activated sludge test was conducted under aerobic conditions in accordance with the OECD 314B guideline (Federle, 2005). A solution of radiolabelled dodecanol (1-¹⁴C) was tested at 9.3 µg/L. After 48 h, 73.9% was mineralized, 20.7% was non-extractable (solids), 5.9% was metabolite, and 0.8% remained as parent. The rate constants for primary biodegradation and mineralization of dodecanol in activated sludge were 113 h^-¹ and 11 h^-¹, respectively.

A simulation of the biodegradation of tetradecanol and hexadecanol in an activated sludge test using similar methods to the sediment studies described above, was conducted under aerobic conditions in accordance with the OECD 314B guideline (Federle, 2005).

 

A solution of radiolabelled tetradecanol (1-¹⁴C) was tested at 10 µg/L. After 48 h, 76.7% was mineralized, 21% was non-extractable (solids), 6.3% was metabolite, and 1.3% remained as parent. The rate constants for primary biodegradation and mineralization of tetradecanol in activated sludge were 86.5 h^-1and 3.4 h^-1, respectively.

 

A solution of radiolabelled hexadecanol (1-¹⁴C) was tested at 10.7 µg/L. After 48 h, 66.3% was mineralized, 17.1% was non-extractable (solids), 11.5% was metabolite, and 2.6% remained as parent. The rate constants for primary biodegradation and mineralization of hexadecanol in activated sludge were 103.4 h^-1and 1.8 h^-1, respectively.

 

The inoculum was activated sludge obtained from Fairfield Wastewater Treatment Plant (Fairfield, OH), which receives predominantly domestic wastewater. The disappearance of parent and progression of metabolite formation and decay were monitored over time by thin layer chromatography with radioactivity detection. Production of CO₂was determined by comparing total radioactivity in a bioactive treatment compared to that in an abiotic control using liquid scintillation counting (LSC).

 

This biodegradation simulation test satisfied the guideline requirements for the OECD 314 B simulation tests to assess the biodegradability of chemicals discharged in wastewater.