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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Following GLP
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
22 July, 2010
Deviations:
no
Principles of method if other than guideline:
not relevant
GLP compliance:
yes
Test material information:
Composition 1
Specific details on test material used for the study:
Identity: 4,4’-Oxybis(benzenesulfonyl hydrazide) (OBSH)
CAS No.: 80-51-3
EC No.: 201-286-1
KIT Code No.: K-5450
Lot No.: 201512001
Appearance: White fine powder
Purity: 99.5~100%
Expiry date: December, 2016
Storage conditions: Room temperature / Protect from moisture and light

Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
to be decided
Test organisms (species):
activated sludge
Details on inoculum:
Activated sludge was collected from Nivå wastewater treatment plant on 13 November 2017. After addition of 75 mL synthetic sewage to 7-8 L sludge, the sludge were stored overnight with aeration at room temperature. Sludge was separated from the water phase by centrifugation (10 min. at approx. 1,500 rpm - approx. 15,000 m/sec2). Then the sludge was re-suspended in tap water and the washing procedure was repeated. The sludge was sieved through a 1-mm sieve and finally re-suspended in tap water. The concentration of the suspended solids (SS) in the re-suspended sludge was determined as descirbed in DS/EN 872 to be 23.4 g SS/L. The sludge was stored at 5oC overnight. On the test day, the activated sludge was aerated until use.

A preliminary respiration rate of the sludge, measured in a mixture consisting of 10% sludge, synthetic seage medium and Milli-Q water, was estimated to be 64 mg O2/L/hr (corresponding to 27 mg O2/g SS/hr). The respiration rate fulfilled the validity criterion af >20 mg O2/g SS/hr).

The final sludge concentrations in the test mixtures were 2.26 - 2.47 gSS/L.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
180 min
Post exposure observation period:
no
Hardness:
No data
Test temperature:
21 (20.5-21.8) oC
pH:
7.5 ± 0.5 (start of test); 7.7 -7.9 (at completed test)
Dissolved oxygen:
3.7-7.0 (controls, 30 minutes)
2.5-7.0 (controls, 180 minutes)
Salinity:
NA
Conductivity:
NA
Nominal and measured concentrations:
Nominal
Details on test conditions:
Please refer to information stated in the section above
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
911 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: Confidence interval: 801-1069
Key result
Duration:
30 min
Dose descriptor:
other: EC20
Effect conc.:
244 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: Confidence interval: 201-283
Key result
Duration:
180 min
Dose descriptor:
EC50
Effect conc.:
641 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: Confidence interval: 593-697
Key result
Duration:
180 min
Dose descriptor:
other: EC20
Effect conc.:
186 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks on result:
other: Confidence interval: 164-207
Results with reference substance (positive control):
The results obtained with the reference item 3,5-dichlorophenol, showed an EC50 of 10.7 mg/L (30 min) and 6.7 mg/L (180 min). The EC50 was within the 2 to 25 mg/L range, and it was considered acceptable for the test

No data

Validity criteria fulfilled:
yes
Conclusions:
30 min EC50 = 911 mg/L (respiration rate)
30 min EC20 = 244 mg/L (respiration rate)
180 min EC50 = 641 mg/L (respiration rate)
180 min EC20 = 186 mg/L (respiration rate)
Executive summary:

The test item was tested according to OECD Guideline no 209: Activated Sludge, Respiration Inhibition Test. The study was conducted according to GLP.

Resulting EC50 = 911 mg/L (30 min), EC20 = 244 mg/L (30 min), EC50 = 641 mg/L (180 min) and EC20=186 mg/L (180 min).

Description of key information

The test item was tested according to OECD Guideline no 209: Activated Sludge, Respiration Inhibition Test. The study was conducted according to GLP.

Resulting EC50 = 911 mg/L (30 min), EC20 = 244 mg/L (30 min), EC50 = 641 mg/L (180 min) and EC20=186 mg/L (180 min).

Key value for chemical safety assessment

EC50 or LC50 for microorganisms:
641 mg/L

Additional information