Registration Dossier
Registration Dossier
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EC number: 232-259-2 | CAS number: 7803-49-8
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
Depending on local conditions and existing concentrations, disturbances in the biodegradation process of activated sludge are possible
Key value for chemical safety assessment
Additional information
There are three tests available on the effect of bis(hydroxylammonium) sulphate to respiration inhibition of activated sludge (BASF 1979, BASF 1984, BASF 2007).
Due to insufficient documentation, the two older studies (BASF 1979, 1984) have been assessed as not reliable. However, in both tests a concentration-dependent inhibition of microbial respiration was observed starting at concentrations of 0.5 - 1 mg/l. The EC20s determined in the studies were 0.6 and 1.0 mg/l.
In another study, the inhibition of oxygen consumption by activated sludge was investigated according to OECD 209 (BASF AG 2007). Activated sludge was obtained from a municipal wastewater treatment plant, test concentrations ranged from 0.05 to 504 mg/L (nominal). After 180 minutes incubation at 20 ± 2 °C the respiration rates were recorded. An EC10 of 0.28 mg/l hydroxylamine was determined. The PNECmico-organisms was derived from the EC10 using an assessment factor of 10.
"Bis(hydroxylammonium)sulphate is known to inhibit microbial activity, also in sewage treatment plants. Other findings (e.g. Amarger & Alexander 1968), indicate an inhibition of microbial activity due to high concentrations of hydroxylamine. However, since hydroxylamine is an intermediate in the nitrification process, in lower concentrations hydroxylamine is expected to be degraded biologically to nitrite (e.g. Jetten et. al. 1997).
Taking these findings together with the data concerning transformation of bis(hydroxylammonium)sulphate, it can be assumed that the toxicity to microorganisms is associated with high concentrations of the hydroxyl-ammonium ion or hydroxylamine. In sewage treatment plants pH is buffered to pH 8 where the hydroxyl-ammonium ion is present only in very low concentrations. In addition to that, hydroxylamine (free base) is expected to decompose rapidly due to abiotic processes. The remaining concentration is not expected to inhibit microbial activity. Hence it can be assumed that additional biological degradation occurs in the waste water treatment plant." (EU-RAR Draft 14. May 2008)
Reference:
ECB (2008). EU-RAR Draft, Bis-(hydroxylammonium)sulphate, CAS: 10039 -54 -0,14. May 2008
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