Grey water reuse system will teach youngsters much about the behaviour of water, soil and plants and should be part of the curriculum in school education, advises water expert S.Vishwanath
Grey water is the term used to describe water flowing from bathrooms and cloth wash areas which predominantly have only soaps in them. Water from the kitchen sinks used to just rinse vegetables or dishes is also considered as grey water. In the Indian context water from the toilets and kitchen sink which has organic substance and fats would be considered black water.
Grey water is relatively easier to treat and re-use as compared to black water since it has relatively less materials to decompose and treat. However grey water stored for long can really smell and it too can have high pathogen loads.
Simple steps in treating grey water would include a basic filter to remove large particles. This could be simple ‘sand and gravel' filter or a mesh filter. The mesh could be of metal or even cloth. The mesh filter will need to be cleaned regularly and best is on a daily basis.
Imagine a bucket half-filled with gravel and sand and grey water is allowed to come in from the top and picked up after the filtering at the bottom through a pipe. The mesh filter is generally put along with a sediment trap so as to remove the heavy particles such as what may come from the kitchen sink while rinsing vegetables, rice or dal.
After a basic filter, an oil and grease trap could be used to separate these if any. The oil and grease trap is a simple device which allows the fat to float up and collects water from an inverted ‘P trap' for further processing. The oil and grease trap also needs to be regularly cleaned and the top layer of oil skimmed off and put into a compost heap if possible.
Baffles, stones and mesh
The water that flows from an oil and grease trap then is allowed to pass through a series of baffles, usually three, in a large lined container. This container is filled with large stone at the top, smaller stones and finally a mesh is put on the stone and then sand is placed on it.
On the sand a small layer of soil can be placed and plants such as cat-tails put. The roots of the plants will go into the water, absorb it and evapo-transpire it. Other plants such as coriander or chillies can also be put. The outlet from this can then be either put into a pond or a small recharge pit to go into the ground.
Grey water treatment systems need space and should preferably be located on the sunny side of the plot. The less detergents and soap we use the better the quality of water. Reuse and less use is the mantra of our times and a grey water reuse system will teach youngsters much about the behaviour of water, soil and plants. This can very easily fit into schools as an educational system too. www.rainwaterclub.org
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