Grey Water
The Effect of the Solar Water Purifier on the Chemical and Physical Properties of Grey Water
After processing by the Solar Water Purifier, all the parameters in the table above will be converted into acceptable values for potable water. For example, after processing, the Total Dissolved Solid (TDS) content will lie in the range 2 – 10 mg/L (or ppm). The pH value will be very closely neutral, with a value of 7.0.
The special glass cover on the Solar Water Purifier transmits both infra-red radiation to heat the water and ultra-violet radiation to break the DNA bonds of any bacteria, virus or algae.
The prolonged exposure throughout the day to the available ultra-violet radiation from the sun effectively kills any germs present in the impure water. Germs cannot cross a vapour barrier and therefore cannot reach the flow of pure water on the underside of the glass surface.
Colony forming units (cfu) are reduced to extremely low values, almost beyond an easy detection level. Regular flushing of the Solar Water Purifier with impure water will result in the removal of any residue resulting from the input grey water.
Cautionary Notes:
1. Currently the standard unit of the Solar Water Purifier can purify grey water to a purity level of 5 – 20 parts per million (ppm) of totally dissolved solids (TDS). However, this level of impurity can still include minute and harmless amounts of the soaps, detergents and scents mentioned above. Many humans are super-sensitive to such odours and tastes. These undesirable characteristics can be reduced to closely zero levels by passing the pure output water from the SWP through an activated charcoal filter. The resultant output water is then perfectly safe and palatable for drinking purposes.
2. pH is a measure of the acidity and alkalinity of a liquid. Some soaps and detergents can be aggressively alkaline. Grey water with an initial pH value greater than around 9.0 is likely to degrade the plastic material of the absorber tray on the Solar Water Purifier. Our Research Division is currently investigating other plastics with a wider range of pH tolerances to be used for the absorber tray.
