Science Buddies: "Ask an Expert"

Hello,
I am Abhi.i am studying in 9th grade.I am doing a science project on saving water.Under this I have selected a theme of watering plants with greywater.I have two questions.

a) To what extent the soil/ground water table will be affected because of using grey water. Using grey water should not affect these. Is it not?

b) Are the veg/fruits we are getting out of these plants safe for eating. (If more acidic / alkaline ?).

Please answer these questions.

Thank You

Abhi --

I think this is a great topic for a science project. Regarding your questions though, I'm not sure if anybody will be able to give you a definitive answer, because the whole subject of grey water seems to be undergoing a lot of debate. There is one side that feels it is totally safe to recycle grey water for use in watering plants and other things, and the other side that believes grey water contains enough pollutants that it shouldn't be recycled, and instead should be sent to the water treatment plant with the rest of the sewage.

In case you haven't seen it already, here is the wikipedia article discussing this topic:

http://en.wikipedia.org/wiki/Greywater

Unfortunately the wikipedia article is pretty disorganized and difficult to follow, but it does seem to contain arguments from both camps. Here's a quote from the article specifically about the use of grey water for watering plants:

Greywater from the shower or bath is generally great quality water for the garden. The soap levels at the dilutions typical are actually good for the garden as they are a wetting agent. When laundry greywater is diverted to the garden then the laundry products must be chosen carefully to ensure phosphate and salt levels are low, and the pH balance is neutral. Independent reviews provide detailed information on laundry products. Basic guidelines are also available from system suppliers. It is essential that greywater is diverted to sewer when garden-unfriendly products are being used.

My suggestion in this case would be to design a series of science experiments that actually helps you to determine your own answer to the questions you posed, rather than trying to research the answers in advance. (I know that you're probably required to do some background research in advance, but in this case, the questions you are asking don't seem to have solid well-known answers. Maybe another expert on these forums will chime in and give you a more definite answer.)

--Rajeev