Trichloro(hexadecyl)silane

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
The synthetic sewage feed (16 ml) and an adequate amount of the test substance loading were mixed and made up to 250 ml with Milli-RO water in a 1 litre bottle. The pH was determined. Thereafter 250 ml activated sludge was added. This was the start of the test. The mixture was then aerated during the contact time, using a pipette as an aeration device.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Laboratory culture: Municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Preparation of inoculum for exposure: The sludge was coarsely sieved, washed and diluted with ISO-medium. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (3.0 g/l of sludge, as used for the test). The pH was 7.7 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic sewage feed was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.

Test type:

static

Water media type:

freshwater

Total exposure duration:

3 h

Test temperature:

18.7 and 22.0°C

pH:

7.5 ± 0.5 (7.3-7.5)

Nominal and measured concentrations:

In a combined limit/range-finding test loading rates of 10, 100 and 1000 mg/l were tested.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material: All glass bottles/vessels.
- Aeration: yes
- No. of vessels per concentration (replicates): The highest loading rate was tested in triplicate, lower concentrations consisted of one replicate. In addition, blankcontrols and a nitrification control of the sludge were included.
- No. of vessels per control (replicates): 3


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Adjusted ISO medium, formulated using RO-water (tapwater purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) with
the following composition:
CaCl2.2H2O 211.5 mg/l
MgSO4.7H2O 88.8 mg/l
NaHCO3 46.7 mg/l
KCl 4.2 mg/l


OTHER TEST CONDITIONS
- Adjustment of pH: Since, it is preferred that test solutions have a neutral pH, the pH was adjusted to pH 7.5 ± 0.5 with 1 N NaOH.


EFFECT PARAMETERS MEASURED : The influence of Trichloro(hexadecyl)silane on the respiration rate of activated sludge was investigated
after a contact time of 3 hours.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Reported statistics and error estimates:

the combined limit/range-finding test no statistically significant inhibition of the respiration rate of the
sludge was recorded at and below a loading rate of 1000 mg Trichloro(hexadecyl)silane per litre (Two
Sample t-Test : α=0.05 Toxstat

Under the conditions of this present test Trichloro(hexadecyl)silane was not toxic to waste water

(activated sludge) bacteria at or below a loading rate of 1000 mg/l (NOEC).

Validity criteria fulfilled:

yes

Description of key information

Toxicity to microorganisms: 3-h EC50 >1000 mg/L; NOEC >= 1000 mg/L (OECD 209) 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The influence of trichloro(hexadecyl)silane on the respiration rate of activated sludge was investigated after a contact time of 3 hours. The study procedures described in this report were based on OECD 209. In a combined limit/range-finding test loading rates of 10, 100 and 1000 mg/L were tested. No statistically significant inhibition of the respiration rate of the sludge was recorded at and below a loading rate of 1000 mg trichloro(hexadecyl)silane per litre. Furthermore, there was no oxygen uptake from abiotic processes and the results at 1000 mg/L with a nitrification inhibitor showed that the heterotrophic inhibition of the respiration rate was in general comparable to the total inhibition. In conclusion, trichloro(hexadecyl)silane was not toxic to waste water (activated sludge) bacteria at or below a loading rate of 1000 mg/L (NOEC).