Safety Data Sheets (SDSs) are the best general source of information available for any chemical, and they should be consulted as a first step in assessing the risk associated with disposal.
Due to toxicity to the aquatic environment, potassium permanganate solution should not be allowed to enter drains or waterways. Therefore, the safe and recommended practice for disposal of this solution is through a licensed waste disposal contractor.
Alternatively, this solution can be stored for future use. Care should be taken when preparing and storing since potassium permanganate solutions are not stable and decompose when reducing agents are present. It is affected by light and is best stored in an amber glass bottle. An additional measure to exclude light is to wrap the bottle in aluminium foil.
A dilute solution of potassium permanganate is not classified as hazardous in general. It is used as an oxidising agent, a disinfectant, as an anti-algal agent, in metal cleaning, in tanning, bleaching, and as a preservative for fresh flowers and fruits.
However, potassium permanganate is very toxic to the aquatic environment, which is why it is not suitable for being disposed of down the sink and into waterways.
Most toxicity tests have been carried out using soluble Mn(II) salts. Potassium permanganate is a highly soluble salt containing Mn(VII) ions. For example:
- For algae and protozoa, there is a wide range of toxicity values: the most sensitive species are marine diatoms and freshwater algae being affected by amounts as low as 1.5 mg manganese/litre.
- Aquatic invertebrates are affected by amounts ranging from 0.8 to 1389 mg manganese/litre.
- A significant reduction in survival and hatching of crab embryos at >0.01 mg manganese/litre in seawater was found.
- Fish are affected at levels from 2.4 to 3350 mg manganese/litre.
- Significant embryonic mortality was observed in trout eggs at 1 mg manganese sulfate/litre.
- A single embryo-larval test was identified for amphibians at 1.4 mg manganese/litre.
Read more at http://www.inchem.org/documents/cicads/cicads/cicad63.htm#7.0 7.2 Toxicity to the aquatic environment.
ChemCentre, Curtin University, Bentley W.A. May 2015. With assistance from the Scientific Services Division. Personal communication
Howe, P.D, Malcolm, H.M, Dobson, S. 2004 ‘Manganese and its compounds: Environmental aspects’ WHO: Geneva http://www.inchem.org/documents/cicads/cicads/cicad63.htm#7.0
‘Manganese and compounds’ Australian Government Department of Environment website http://www.npi.gov.au/resource/manganese-compounds (Accessed May 2015)