Household water treatment using commercial products
There are several examples of commercial products available for household water treatment:
Aluminum sulphate plus calcium hypochlorite
This is a combined coagulant–flocculant–disinfectant powder mixture produced for water treatment. The sachet contains aluminium sulphate as coagulant and a flocculant for reducing turbidity, and calcium hypochlorite as a disinfectant to kill bacteria and viruses (Figure 10.10).
The directions for using this powder are as follows:
- Put 20 litres of raw water into a clean bucket.
- Open the sachet (2.5 gr) and add the contents to the bucket.
- Stir rapidly with a stick for 2 minutes (to disperse the chemicals) and then stir slowly for an additional 3–4 minutes (to help the solid particles come together to form larger particles or flocs).
- Wait for at least 20 minutes for the flocs to settle and the micro-organism to die. The longer you wait, the clearer the treated water will be.
- Strain the water through a thick cotton cloth into a safe water storage container, from which it can be consumed.
- Dispose of the material that settles at the bottom of the bucket by burying it.
Sodium dichloroisocyanurate (NaDCC) is a disinfectant (Figure 10.11). The tablets are easier than bleach to store, handle and transport. One tablet contains 67 mg of NaDCC and can treat 20 litres of clear water. The tablet has to be dissolved in the water by vigorous mixing, and a contact time of 30 minutes is necessary. If the water is turbid, two tablets will be needed.
P&G Purifier of water (ferrous sulphate plus calcium hypochlorite)
P&G Purifier of Water is the brand name of a combined coagulant, flocculant and disinfectant product produced by Procter & Gamble (Figure 10.12). The coagulant/flocculant is ferrous sulphate and the disinfectant is calcium hypochlorite. It can be used to treat raw source waters with a wide range of turbidity and pathogen load. This water treatment chemical allows flocculation to take place and helps to remove Giardia and Cryptosporidium cysts that are resistant to chlorine disinfection. (A cyst is a dormant stage in the life cycle of some protozoa and bacteria that is resistant to adverse environmental conditions and therefore difficult to destroy.) P&G Purifier of Water comes in sachets and one sachet is needed to treat 10 litres of water.
The procedure for using P&G Purifier of Water is illustrated in Figure 10.13.