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Grey water – shades of grey matter

grey water

When water is scarce, our gardens take strain.  One of the ways to stave off parched lawn syndrome is diversion of grey water to the thirsty garden parts.  Just in case there is some confusion, grey water is any used water that has not been part of the food preparing or digesting process.  It is mostly clean, in fact very clean because it would contain quite abit of soap, shampoo, toothpaste and anything else that lathers.  There will also be a small amount of organic material in the form of skin cells and even smaller amounts of bodily extrudate.

For life in the soil, grey water is a mixed blessing.  Although the liquid component is very welcome, the attendant du parfum toilette presents a puzzling conundrum.   In grey water there is very little organic material that is of use to microbes living in the soil.  Although there are some nutrients in the grey water and phosphorous is one of these, the quantities far exceed the demand.  Soap is the ticking time bomb.  Most soaps contain active ingredients that act as solvents in water.    When soap loses its active functionality it very quickly dissolves and in so doing increases the baseline conductivity of the water.  In other words, the water becomes brackish.

If there is not a decent rain water flushing regime a soil could become saturated with dissolved salts.  Most plants shy away from salty water and it is not surprising that low plant density areas, such as found in the Karoo, are also areas in which ground water is distinctly brackish.

Grey water

Salt water poisoning is a slow process - it could take a lifetime.  Some soils are more forgiving than others.  In many instances the effects of dissolved soaps will not be registered.  If there is any doubt, our recommendation is to install a grey water treatment system that pays attention to conductivity.  Conductivity is the yardstick by which engineers measure the salt content of water.

"The lamps are going out all over Europe, we shall not see them lit again in our life-time", British Foreign Secretary Sir Edward Grey remarked to a friend on the eve of Britain's entry into the First World War.

Non sequitur - or perhaps there is some light in the grey after all.


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