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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

There was no effect on the microorganisms up to approximately 8 g/L over a period of 37 days. With respect to the high NOEC values, sodium sulfate is not expected to be hazardous for activated sludge.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
8 g/L

Additional information

Three publications were found which described tests on activated sludge bacteria, motile protozoa and stalked ciliates. Two publications from Tokuz and Eckenfelder (1979) and Tokuz (1986)

described the same experiment, therefore only two different studies were found. Both were found reliable with restrictions as the studies were not performed according to standardised guidelines, but were described with enough details.

Tokuz & Eckenfelder and Tokuz found that the increasing concentrations of sodium sulfate did not cause any appreciable deterioration in effluent quality in terms of effluent suspended solids and COD. The eflluent COD stayed more or less at a constant level and suspended solids concentration increased slightly. The rate of increase of salinity was much faster for the sodium sulfate system but no negative effects were seen. Effects were measured by the efficiency of DOC removal.

There was no effect on the microorganisms up to approximately 8 g/L over a period of 37 days. With respect to the high NOEC values, sodium sulfate is not expected to be hazardous for activated sludge.