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EC number: 215-481-4 | CAS number: 1327-53-3
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- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
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- Long-term toxicity to aquatic invertebrates
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Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
- Endpoint:
- activated sludge respiration inhibition testing
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Not a guideline study, but well reported and conducted study
- Qualifier:
- equivalent or similar to guideline
- Guideline:
- other: APHA (1989): Standard methods for the examination of water and wastewater, 17th ed. American Public Health Association
- Principles of method if other than guideline:
- The study investigated the effect of arsenic (As(III)) and As(V)) on the respiration rate of activated heterotrophic sludge microorganisms.
- GLP compliance:
- not specified
- Specific details on test material used for the study:
- Additionally, analytical grade arsenic pentoxide (As2O5), purchased from Merck, was tested.
- Analytical monitoring:
- no
- Vehicle:
- no
- Test organisms (species):
- activated sludge, domestic
- Details on inoculum:
- A sequencing batch reactor (SBR) was used to simulate the activated sludge process and to provide biomass for the toxicity tests. The SBR was operated in a 24-h fill and draw cycle, each cycle consisted of four stages: FILL (10 min), REACT (22.5 h with aeration), SETTLE (1 h) and DECANT (20 min). Activated sludge from a municipal wastewater treatment plant was used to seed the reactor. Synthetic wastewater with a known COD concentration was used as a feed and phosphate buffer was added to maintain a constant pH. When biomass was acclimatized to the feed and steady state had been attained, activated sludge of known
concentration of suspended solids was mixed in a 300 mL BOD bottle with the appropriate amount of feed to yield a food-to-microorganisms (F/M) ratio of 0.1 mg COD/ mg MLVSS, and the test compound at various concentrations. - Test type:
- static
- Water media type:
- freshwater
- Limit test:
- no
- Total exposure duration:
- 10 d
- Test temperature:
- 20 ± 1 °C
- pH:
- 7.0 ± 0.2
- Nominal and measured concentrations:
- Not reported
- Details on test conditions:
- TEST SYSTEM
- Test vessel: 300 ml BOD bottle
- Aeration: yes
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- Sludge concentration (weight of dry solids per volume): not reported
- Nutrients provided for bacteria: Synthetic wastewater (ratio of 0.1 mg COD/mg MLVSS)
- Nitrification inhibitor used: Thiourea (at a final concentration of 10 mg/L)
OTHER TEST CONDITIONS
- Adjustment of pH: phosphate buffer was added to maintain a stable pH
EFFECT PARAMETERS MEASURED:
- Respirometric measurements of specific oxygen uptake rate (sOUR) using an oxygen probe - Reference substance (positive control):
- no
- Key result
- Duration:
- 2.5 d
- Dose descriptor:
- EC50
- Effect conc.:
- 6.1 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- element
- Basis for effect:
- inhibition of total respiration
- Remarks:
- respiration rate
- Remarks on result:
- other: lowest reported EC50 for As (III)
- Duration:
- 5 d
- Dose descriptor:
- EC50
- Effect conc.:
- 7.3 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- element
- Basis for effect:
- inhibition of total respiration
- Remarks:
- respiration rate
- Remarks on result:
- other: for As (III)
- Duration:
- 10 d
- Dose descriptor:
- EC50
- Effect conc.:
- 10.6 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- element
- Basis for effect:
- inhibition of total respiration
- Remarks:
- respiration rate
- Remarks on result:
- other: for As (III)
- Duration:
- 2.5 d
- Dose descriptor:
- EC50
- Effect conc.:
- 81 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- element
- Basis for effect:
- inhibition of total respiration
- Remarks:
- respiration rate
- Remarks on result:
- other: lowest reported EC50 for As(V)
- Duration:
- 5 d
- Dose descriptor:
- EC50
- Effect conc.:
- 97 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- element
- Basis for effect:
- inhibition of total respiration
- Remarks:
- respiration rate
- Remarks on result:
- other: for As(V)
- Duration:
- 10 d
- Dose descriptor:
- EC50
- Effect conc.:
- 198 mg/L
- Nominal / measured:
- nominal
- Conc. based on:
- element
- Basis for effect:
- inhibition of total respiration
- Remarks:
- respiration rate
- Remarks on result:
- other: for As(V)
- Validity criteria fulfilled:
- not specified
- Remarks:
- Not assessable (control OUR not reported; no reference toxicant)
- Conclusions:
- In an activated sludge respiration inhibition test, the lowest EC50 for respiration inhibition was reported for 2.5-d old sludge at 6.1 mg As/L (nominal, As(III).
Reference
Description of key information
In an activated sludge respiration inhibition test, the lowest EC50 for respiration inhibition was reported for 2.5-d old sludge at 6.1 mg As/L (nominal, As(III).
Key value for chemical safety assessment
- EC50 for microorganisms:
- 6.1 mg/L
Additional information
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