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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Waste water from NaOH production sites is coming from the salt electrolyses and is an inorganic wastewater stream. For this reason it is not feasible to treat it biologically. Therefore, wastewater streams from NaOH production sites will normally not be treated in biological waste water treatment plants (WWTPs). Direct discharging of NaOH solutions into municipal wastewater must be avoided unless neutralization is carried out. NaOH may be used beneficially, however, for pH control of acid wastewater streams that are treated in biological WWTP’s (EU RAR, 2007). Consequently, the pH of the influent of a municipal wastewater treatment plant is neutral and therefore, there is no exposure of micro-organisms.

Key value for chemical safety assessment

Additional information

No valid studies are available for the endpoint toxicity to microorganisms. Despite of this, there is no need for additional aquatic toxicity testing with NaOH, as all available tests resulted in a rather small range of toxicity values and there are sufficient data on the pH ranges that are tolerated by major taxonomic groups (EU RAR of NaOH, 2007; section 3.2.1.1.4, page 30).