Kerosine (Fischer-Tropsch), full-range, C8-16-branched and linear

Biodegradation in water: screening tests

Description of key information

Key studies: 
1) Two samples were tested, whereby one sample just met the stringent ’10-day window’ criterion, and the second just failed to meet it: 74-54%  
degradation in 28 days; conclusion: readily biodegradable (OECD 301F).
2) One sample was tested, whereby the stringent ’10-day window’ criterion was met: >75%  degradation in 28 days; conclusion: readily 
biodegradable (OECD 301F).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

A large data set is available for whole product fractions of GTL Kerosine and related Fischer-Tropsch substances. The total solubility of constituents of this substance is <1 mg/l. Therefore, when the test substance is loaded into the medium at concentrations higher than this limit, the extent and rate of dissolution into water can be expected to influence the result of a ready biodegradation test. In such studies no measurements of the dissolved organic carbon from the substance are possible, and therefore it cannot be known how much bioavailable (dissolved) constituents were present. The highest levels of reported degradation are those which should be given most weight in hazard assessment and risk characterisation.

During biodegradation tests conducted using GTL Kerosine and related UVCB hydrocarbon products, it is anticipated that a sequential biodegradation of the individual hydrocarbon structures takes place. The 10-day window should not be applied to interpret the results of such tests (OECD, 2006).

The following discussion includes biodegradation test results for GTL Kerosine and closely-related substances.

Table: Ready biodegradation - Overview of screening tests for biodegradation in water

Method	Results	Remarks	Reference
Test type: ready biodegradability activated sludge, domestic (adaptation not specified) OECD Guideline 301F (Ready Biodegradability – Manometric Respirometry)	% Degradation of test substance:   Test 1: 75% after 28 d ( O2consumption)   Test 2: 74% after 28 d ( O2consumption)	2 (reliable with restrictions) Key Study read-across from supporting substance (structural analogue or surrogate) Test material (EC name): Distillates (Fischer-Tropsch), C8-26 - branched and linear (CAS: 848301-67-7)	Battersby and Bumpus, 2001
Test type: ready biodegradability activated sludge, domestic (adaptation not specified) OECD Guideline 301F (Ready Biodegradability – Manometric Respirometry)	% Degradation of test substance:   Test 1: >75% after 28 d ( O2consumption)	2 (reliable with restrictions) Key study read-across from supporting substance (structural analogue or surrogate) Test material (EC name): Distillates (Fischer-Tropsch), C8-26 - branched and linear (CAS: 848301-67-7)	Albertus and Phillips (2005)
Test type: ready biodegradability activated sludge, domestic (adaptation not specified) OECD Guideline 301F (Ready Biodegradability – Manometric Respirometry)	% Degradation of test substance:   68-70% ( O2consumption)	2 (reliable with restrictions) Supporting study read-across from supporting substance (structural analogue or surrogate) Test material: C11-15 n- and iso-alkanes (52%) and C10-15 cycloalkanes (46%)  (CAS: 64742-47-8)	Battersby, Bumpus and Eagle, 1997a
Test type: ready biodegradability activated sludge, domestic (adaptation not specified) OECD Guideline 301F (Ready Biodegradability – Manometric Respirometry)	% Degradation of test substance:   80% after 28 d ( O2consumption)	2 (reliable with restrictions) Supporting study read-across from supporting substance (structural analogue or surrogate) Test material: C9-13 n- and iso-alkanes (60%) and C9-11 cycloalkanes (38%) (CAS: 64742-48-9)	Battersby, Bumpus and Eagle, 1997b
Test type: ready biodegradability activated sludge, domestic (adaptation not specified) OECD Guideline 301B (Ready Biodegradability – CO2Evolution)	% Degradation of test substance:   14.3% after 28 d (CO2evolution)	4 (not assignable) disregarded study experimental result Test material (EC name): Kerosine (Fischer-Tropsch), full range, C8-16 - branched and linear (CAS: 848301-66-6)	Zhang, 2009
Test type: ready biodegradability activated sludge, domestic (adaptation not specified) OECD Guideline 301B (Ready Biodegradability – CO2Evolution)	% Degradation of test substance:   Test 1: 8.2% after 28 d (CO2evolution)   Test 2: 39.5% after 28 d (CO2 evolution)	4 (not assignable) disregarded study read-across from supporting substance (structural analogue or surrogate) Test material (EC name): Distillates (Fischer-Tropsch), C8-26 - branched and linear (CAS: 848301-67-7)	Xue Han, 2009a

 

A biodegradation test has been performed using Kerosine (Fischer-Tropsch), full range, C8-16-branched and linear (Zhang, 2009). The study was conducted in accordance with OECD Guideline 301B. The test substance was introduced into the test system by being adsorbed on to silica gel. The test substance concentration was 15.5 and 15.9 mg C/l in the two tests. There is no indication of steps being taken to minimise or prevent evaporation during test substance loading or during the test. The inoculum was non-adapted activated sludge sampled from a municipal waste water treatment plant treating predominantly domestic sewage. The concentration of inoculum in the test system was 30 mg suspended solids/l. The study determined, as far as possible, the absence of inhibition of micro-organisms by the test substance. Assessment of biodegradation in both tests was made by CO₂analysis only. At the end of the 28 d test period, 14.3% degradation was reported. The kinetics appear to show that the degradation proceeded smoothly with a short period of slightly increased degradation in the final days of the test. In view of the use of CO₂analysis only, it is not possible to interpret the results further than this or discriminate between constituents. The study was conducted in accordance with GLP. Whilst there is not strong evidence that the test had significant methodological deficiencies, the result showing such low degradation is surprising for this carbon chain range, conflicting with findings in other tests with similar samples, and casts significant doubt on this study, which is therefore disregarded for the present purpose.Kerosine (Fischer-Tropsch),full range, C8-16-branched and linearand was not readily biodegradable in this study.

In the absence of reliable data for GTL Kerosine, data have therefore been read-across from the related substance GTL Gasoil (Distillates (Fischer-Tropsch), C8-C26, branched and linear). This substance is produced using the same Fischer-Tropsch process as GTL Kerosine and contains all of the same hydrocarbon constituents, but the product fraction additionally contains longer carbon chain lengths, up to C26, compared to C16 in GTL Kerosine. Since biodegradation is slower for longer chain lengths (see Table 4.1.2), this is a conservative approach and read-across is valid.

Battersby and Bumpus (2001) report results of OECD 301 F tests performed on two samples of Distillates, (Fischer-Tropsch), C8-26 – branched and linear (sample nomenclature in the test report SMDS-1 and SMDS-2; no further information is available about sample characteristics or composition, though it is stated that both samples contained an antioxidant additive). The substances were introduced on to glass-fibre filter paper suspended over foil; the paper and foil were both added to the flask. The test substance concentration was 30 mg C/l. For neither method is there any indication of steps being taken to minimise or prevent evaporation during test substance loading or during the test. The inoculum was non-adapted activated sludge sampled from a municipal waste water treatment plant treating predominantly domestic sewage. The concentration of sludge in the test system was 30 mg as dry solids/l. Assessment of biodegradation in both tests was made by oxygen consumption analysis only. At the end of the 28 d test period, high levels of degradation were achieved for both samples: Based on fraction of the theoretical oxygen demand (ThOD), SMDS-2 reached 75% removal and the 10-day window criterion was met. SMDS-1 reached 74% removal, rapidly biodegradable but for this sample the 10-day window was not met. By comparison, the same study also reported a result of 60% ThOD in 28 days for an ultra low sulfur diesel fuel (ULSD), and values in the range 59% – 68% removal for blends of the SMDS samples with ULSD. The study concludes that one of the two samples of SMDS (Distillates (Fischer-Tropsch), C8-26-branched and linear) is readily biodegradable meeting the 10-day window; the other sample fails the 10-day window criteria by a small margin. The plotted degradation levels over time demonstrate a relatively smooth ongoing increase in degradation.

The ready biodegradability of a comparable product (Sasol SPD^TMDiesel) has been studied using the manometric respirometry method, OECD 301F (Albertus and Phillips, 2005). The composition is not discussed in the study report but an average carbon number of C13 is evident in the ThOD calculation. The substance was loaded onto glass fibre filter papers and added to the test flasks. The test substance concentration was ca. 27 mg/l. There is no indication of steps being taken to minimise or prevent evaporation during test substance loading or during the test. The inoculum was ‘return-water’ containing microorganisms sampled from a waste water treatment plant dedicated to treat only domestic sewage. The concentration of sludge in the test system was not stated but it is reported that the oxygen uptake of the inoculum blank was within the acceptable range. The progress of biodegradation was monitored via O₂uptake only. At the end of the 28 d test period, based on fraction of the theoretical oxygen demand (ThOD), greater than 75% removal was achieved and the 10-day window criterion was met. Validity criteria were reported to be met. The raw data were not presented in the report.

A study of the ready biodegradation of Distillates (Fischer-Tropsch), C8-26-branched and linear has been conducted (XueHan, 2009a). The study was conducted in accordance with OECD Guideline 301B. In this study two alternative methods were used to introduce the test substance into the test system. In test 1, the substance was adsorbed on to silica gel. The test substance concentration was 16.4 mg C/l. In test 2, the substance was introduced on to glass-fibre filter paper suspended over foil; the paper and foil were both added to the flask. The test substance concentration was 15.3 mg C/l. For neither method is there any indication of steps being taken to minimise or prevent evaporation during test substance loading or during the test. The inoculum was non-adapted activated sludge sampled from a municipal waste water treatment plant treating predominantly domestic sewage. The concentration of inoculum in the test system was 30 mg suspended solids/l. The study determined, as far as possible, the absence of inhibition of microorganisms by the test substance. Assessment of biodegradation in both tests was made by CO₂analysis only. At the end of the 28 d test period, 8.4% degradation was reported for test 1 and 39.5% in test 2. The kinetics show clearly that a plateau was reached early in both tests followed by increasing degradation late in the test (for test 2 in particular a significant increase in percent degradation is seen between days 25 – 28). This is suggestive of rapid degradation of some constituents with a lag period for others. In view of the use of CO₂analysis only, it is not possible to interpret the results further than this or discriminate between constituents. The increased surface area available in the test system associated with the presence of the filter paper may have played a role in the higher degradation levels achieved in test 2. The study was conducted in accordance with GLP. Whilst there is not strong evidence that the test had significant methodological deficiencies, the result showing such low degradation is surprising for this carbon chain range, conflicting with findings in other tests with similar samples, and casts significant doubt on this study, which is therefore disregarded for the present purpose.Distillates (Fischer-Tropsch), C8-26-branched and linear was not readily biodegradable in this study.

A study of ready biodegradability of C11-15 n- and iso-alkanes (52%) and C10-15 cycloalkanes (46%) is available (Battersby, Bumpus and Eagle, 1997a). The tested substance lies within the carbon number range for GTL Kerosine, but some of the long and short chain constituents are not fully represented by the substance used in this test. This method uses the guideline method OECD 301F (manometric respirometry) and is compliant with GLP. The inoculum is municipal WWTP sludge pre-conditioned with filtration and aeration. Alongside the test substance, a positive control, inhibition control and blank were tested. Due to low solubility the test substance (18 µl/l, equivalent to 14 mg/l) was loaded by injection into the test vessels below the surface, with magnetic stirring. The test report does not refer to any visible phase separation. The test substance was degraded by approx. 68-70% after 28 d based on oxygen uptake, but only ca. 48% degradation within the 10-day window occurred. The validity criterion relating to variation between replicates was not met; this was ascribed in the study report to insolubility / volatility of test substance, and assumed not to impact the interpretation. The kinetics display a short initial lag phase; a plateau was not reached by the end of the test. The test substance was considered readily biodegradable not meeting the 10-day window.

A study of ready biodegradability of C9-13 n- and iso-alkanes (60%) and C9-11 cycloalkanes (38%) is available (Battersby, Bumpus and Eagle, 1997b). The test substance lies within the carbon number range for GTL Kerosine, but some of the longer chain constituents are not fully represented by the substance used in this test. This method uses the guideline method OECD 301F (manometric respirometry) and is compliant with GLP. The inoculum is municipal WWTP sludge pre-conditioned with filtration and aeration. Alongside the test substance, a positive control, inhibition control and blank were tested. Due to low solubility (19 µl/l, equivalent to 15 mg/l) the test substance was loaded by injection into the test vessels below the surface, with magnetic stirring. The test report does not refer to any visible phase separation. The test substance was degraded by approx. 80% after 28 d based on oxygen uptake, but only approx. 52% degradation within the 10-day window occurred. The validity criteria were met. The kinetics display a short initial lag phase; a plateau was not reached by the end of the test. The test substance was considered readily biodegradable not meeting the 10-day window.