Safe To Drink

File under: Press Releases, Almost Overly Reassuring.

Apparently, the water in some parts of Cape Town has been tasting a bit funny for a few days now. Cue widespread panic about it being poisonous and deadly and deadly and poisonous.

It’s not.

The slight odour and earthy taste is due to a chemical called Geosmin, which is produced by some naturally occurring bacterial and algae species in the reservoirs around Cape Town. It’s harmless.

It also happened last year.

Says the City:

The presence of Geosmin was confirmed during the routine water quality analyses and tests. Geosmin is non-toxic and not harmful to health.

In this instance, it is originating from the Theewaterskloof Dam – one of the Department of Water Affairs’ (DWA) dams from which the City draws water. It could be caused by the inflow of nutrients to the dam following heavy rainfalls, which increases the growth of the blue-green algae.

The water is perfectly fit for human consumption. Continual water quality monitoring by the City’s South African National Accreditation System (SANAS) accredited laboratory has revealed elevated but still extremely low Geosmin concentrations.

And they are fixing the problem:

The City has begun treating the water in the Theewaterskloof Dam with powdered activated carbon with the aim of returning and maintaining the concentration of Geosmin to below the normal human taste and smell threshold level.

Yeah – read that again. The deadly chemical will still be in there, it’s just that you won’t be able to smell or taste it. It’ll still be eating away at your insides like that heinous Dihydrogen monoxide you insist on consuming.


And how much is that, exactly? Well:

The human nose is extremely sensitive to Geosmin. If you poured a teaspoon of Geosmin into the equivalent of 200 Olympic-sized swimming pools, you would still be able to smell it.

The general threshold for human perception is about 15 ng/l. However people with sensitive noses can detect these compounds in drinking water when the concentration is as low as 8 ng/l.

So, that’s 0.00000008 grams per litre of water. Frankly terrifying.

But hey. Here’s the expert scientific opinion (mine) on all this:

Stop being so dramatic, you desperate attention-seeking prima donnas.

Have a nice day.

Leave a Reply