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Ecotoxicological information

Toxicity to microorganisms

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Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well documented publication which meets basic scientific principles.

Data source

Reference
Reference Type:
publication
Title:
Estimating Toxicity of Organic Chemicals to Activated-Sludge Microorganisms.
Author:
Sun B et al.
Year:
1994
Bibliographic source:
J. Environ. Eng. (N.Y.) 120 (6)

Materials and methods

Principles of method if other than guideline:
=> testing of biodegradation of 1,2,4-TCB by municipal sewage (activated sludge) in closed vessels
=> inhibition effects on microorganisms were measured by reductions in oxygen uptake (BOD)

Activated-Sludge Test Cultures:
The activated sludge test cultures were obtained daily from the Las Cruces Wastewater Treatment Plant, which receives mainly municipal sewage. The reactor (test vessels) received 10 ml of activated sludge each. The test reactors were topped with tap water to reach the final volume of 60 ml, and the control reactors were topped up to 62 ml. All the reactors were then capped with potassium hydroxide pellets in holders attached to the caps. The tests were conducted at the endogenous phase, without any additional growth substrate.

Respirometric Test Procedure:
The tests were run on a 12-reactor, computer-interfaced Comput-OX Respirometer (N-CON Corporation, N.Y.). Except of the control, each reactor was administered with different volumes of the toxicant. The toxicant dose was prepared by dissolving the toxicant in 2 ml of acetone and injecting into the liquid phase in each reactor. The capped reactors were placed in the respirometer water bath, maintained at 25°C with continued supply of oxygen. The data acquisition system was then initiated to monitor and record the oxygen uptake of each reactor; for the next 12 hours.
The inhibition effects were measured in IC50 terms. The percent inhibition at different concentrations of the toxicant was taken as reductions in oxygen uptake rates of spiked reactors compared to that of the control reactor. These percent inhibition values were then plotted against the respective concentrations, and from linear regression analysis of these plots in the range of 2080% inhibition, the concentration causing 50% inhibition, IC50 was determined.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 1,2,4-Trichlorobenzene
- Analytical purity: no data
- Impurities (identity and concentrations): no data

Sampling and analysis

Analytical monitoring:
not specified
Details on sampling:
The tests were run on a 12-reactor, computer-interfaced Comput-OX Respirometer (N-CON Corporation, N.Y.). Details of this system have been presented elsewhere (Cadena et al., 1988). The data acquisition system was initiated to monitor and record the oxygen uptake of each reactor; for the next 12 hours.

Test solutions

Vehicle:
not specified

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The activated sludge test cultures were obtained daily from the Las Cruces Wastewater Treatment Plant, which receives mainly municipal sewage.
The tests were conducted at the endogenous phase, without any additional growth substrate.

Study design

Test type:
static
Water media type:
freshwater
Total exposure duration:
12 h

Test conditions

Test temperature:
25°C
[The capped reactors were placed in the respirometer water bath, maintained at 25°C with continued supply of oxygen.]
Details on test conditions:
Test System:
- Type: closed
- Aeration: continued supply of oxygen


All the reactors were then capped with potassium hydroxide pellets in holders attached to the caps.
The reactor (test vessels) received 10 ml of activated sludge each. The test reactors were topped with tap water to reach the final volume of 60 ml,
and the control reactors were topped up to 62 ml.
Reference substance (positive control):
no

Results and discussion

Effect concentrations
Duration:
12 h
Dose descriptor:
IC50
Effect conc.:
35 mg/L
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

Applicant's summary and conclusion

Validity criteria fulfilled:
not specified