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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
15 February 1999 - 17 May 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
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
- Method:
Test substance: a stock dispersion of the test substance was prepared by dispering 0.2010 g of Ziram in 1000 mL of BOD dilution water
Reference substance: a stock solution of the reference substance was prepared according to the OECD guideline by dissolving 0.1251 g in 5 mL NaOH solution, adjusting the pH to 7.7 with HCl solution, and the making up to 250 mL with Nanopure water
- Controls: yes
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source: oxidation ditch treating domestic sewage, Berkel en Rodenrijs, The Netherlands
- Preparation of inoculum for exposure: the sample was centrifugated and the supernatant discarded. Activated sludge was washed three times by centrifugation (10 min at 2000 rpm = max. 1218 g) and resuspension in tap water twice and in dilution water once. The dry weight of the sludge suspension was determined and the suspension diluted to approximately 4 g/L of mixed liquor suspended solids (MLSS) by addition of dilution water. Then, it was aerated vigorously and kept at approximately 20°C in the dark.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20°C
pH:
7.9
Nominal and measured concentrations:
Nominal concentrations: 0.10, 0.32, 1, 3.2, 10, 32 and 100 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 1 L glass beakers containing 16 mL of synthetic sewage feed, 284 mL of control (dilution water) or treatment solutions and 200 mL of activated sludge
- Aeration: 0.5 to 1 L/min
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: the dilution water was prepared according to NEN standard No. 6634.
- Synthetic sewage feed was prepared according to OECD guideline

EFFECT PARAMETERS MEASURED: respiration inhibition

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
19.2 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
0.32 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
The EC50 for 3,5-dichlorophenol was determined to be 13.2 mg/L, value within the validity range of the OECD guideline (5 to 30 mg/L)
Validity criteria fulfilled:
yes

Description of key information

EC50 (3 h) = 19.2 mg/L (nominal, activated sludge, OECD 209)

Key value for chemical safety assessment

EC50 for microorganisms:
19.2 mg/L

Additional information

The effect of zinc bis dimethyldithiocarbamate (CAS No. 137-30-4) on aquatic microorganisms activity was investigated by Hanstveit et al. (1999). This test was conducted according to OECD Guideline 209, Activated Sludge, Respiration Inhibition Test (1984), under GLP conditions. After 3 hours of exposure to the test substance at 20°C, respiration rate inhibition in activated sludge microorganisms was reported, resulting in a EC50 (3 h) value of 19.2 mg/L.