Silicic acid, calcium salt

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

07/06/2010-11/04/2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

performed under GLP

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Principles of method if other than guideline:

n.a.

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Rheinland Pfalz. 01/11/2007

Test material

Test material information

Constituent 1

Reference substance name:

crystalline calcium silicate hydrate (xonotlite - tobermorite)

IUPAC Name:

crystalline calcium silicate hydrate (xonotlite - tobermorite)

Constituent 2

Reference substance name:

calcium oxosilanebis(olate)

EC Number:

935-756-9

Cas Number:

1344-95-2

Molecular formula:

Xonotlite Ca6Si6O17(OH)2 Tobermorite Ca5(Si6O16)(OH)2.4H2O

IUPAC Name:

calcium oxosilanebis(olate)

Constituent 3

Reference substance name:

Amorphous silicic acid, calcium salt

Molecular formula:

CaSiO3.nH2O

IUPAC Name:

Amorphous silicic acid, calcium salt

Details on test material:

- Name of test material (as cited in study report): crystalline Silicic acid, calcium salt (xonotlite - tobermorite)
- Molecular weight (if other than submission substance): unknown
- Physical state: white solid
- Analytical purity: confidential information
- Composition of test material, percentage of components:crystalline calcium silicate hydrate
- Lot/batch No.: confidential information
- Stability under test conditions: in H2O: 96h
- Storage condition of test material: 20 +/- 5°C

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
none

Sampling and analysis

Analytical monitoring:

not required

Details on sampling:

n.a.

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test item directly added to solution containing inoculum
- Controls: one positive control; two negative controls; control measurements: 2 replicates before and 2 after measuring positive control and test
item, resp.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Preparation of inoculum for exposure: inoculum was taken from the activation basin of the sewage treatments plant D-67480 Edenkoben, the same day as the experiment was performed. In the test facility the sludge was washed with tap water 3 times, then centrifuged and re-suspended in tap water. Dry matter of sludge: 3.46 g suspended solids/L; dry matter in test: 1.73 g suspended solids/L; pH 7.5

Nutrient solution composition ("synthetic sewage"):
Peptone: 16.0g; Meat extract: 11.0g; Urea: 3.0g; NaCl 0.7g; CaCl2*H2O: 0.4g; MgSO4*7H2O: 0.2g; K2HPO4: 2.8g, in 1000ml deionized water

Study design

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

5 minutes

Test conditions

Hardness:

0.91 mmol/L

Test temperature:

19.8 - 21.1 °C

pH:

7.5

Dissolved oxygen:

test parameter

Salinity:

no data

Nominal and measured concentrations:

test item nominal: 1000mg/L; positive control substance 3,5-dichlorophenol: 5, 10 , 20, 40 mg/L nominal

Details on test conditions:

TEST SYSTEM
- Test vessel: glass beakers as test vessels; narrow-neck glass bottles as measuring flasks.
- Aeration: purified air, using Pasteur pipettes; flow approx. 0.75 L/min.
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): one (positive control); 2 x 2 negative controls
- loading rate: dry matter in test: 1.73 g suspended solids/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water
- Total organic carbon:< 1.0 mg/L
- Particulate matter: 0
- Metals: Above detection limit: 0.018 mg/L
- Pesticides: < LOD
- Chloride: 9.0 mg/L
- Ca/mg ratio: 16/1
- Conductivity: 189 nS/cm


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : O2 content; intervals: 5 mins

TEST CONCENTRATIONS
- Test concentrations:
-positive control: 5, 10, 20, 40 mg/L
- test substance: 1000mg/L

Reference substance (positive control):

yes

Remarks:

3.5-dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 2

Key result

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

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50: 9.3mg/L, 95% C.I. 7.6-11 mg/L. The value lies within the recommended range of 5- 30mg/L
- Other: R-square (COD), of log/probit regression = 0.998

Reported statistics and error estimates:

The maximum variation in the control was 19.2 %;

Any other information on results incl. tables

The measured inhibition rates were the following:

Positive control   Inhibition       Treatment       Inhibition

mg/L                            %                  mg/L               %

5                             33.9                 1000              -2.9

10                           51.7                 1000               3.2

20                           71.2

40                           82.3

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

Relevant validity criteria fulfilled

Conclusions:

The 3h-EC50 and 3h-NOEC of Crystalline calcium silicate hydrates on the inhibition of the respiration of activated sludge were > 1000mg/L and ≥ 1000 mg/L ( nominal concentrations) respectively.

Executive summary:

The inhibition of the respiration of acitvated sludge was evaluated according to OECD TG 209 or EU C.11 (Muckle 2010). The study was performed as a limit test using one concentration in duplicate (1000mg/L). Due to the low water solubility the test item was added to the test vessels directly. The dry matter of the activated sludge was determined as 3.46 g suspended solids/L, giving a concentration of 1.73 g suspended solids/L in the test. The EC50 of the positive control was determined as 9.3 mg/l (95 % C.I. 7.6 -11 mg/L), which lies within the range of 5 -30 mg/L.

The following results for the test item crystalline silicate hydrates (xonolite-tobermorite) were determined: 3h NOEC ≥ 1000 mg/L nominal; 3h EC20 >1000 mg/L nominal; EC50 >1000 mg/L nominal.