Will water filter work. Help me out to reach a decision?

See this image http://dl.dropbox.com/u/21019240/image.JPG to understand my question well. In the image, A is my home well in garden. C is the water tank on the third floor which I usually fill using a electric motor fitted in well. From last few months, my well water became dirty due to poor sewage system in my street. I don't have enough money right now and also place in my garden to go for new well or simply make bore in garden. I have an idea. If you see B in image, B is the water filter I want to fit before water tank so that water after being filtered enter in to tank. I believe to get rid of smelly and dirty water with this idea but I wonder will filter be able to filter all water? When I shall turn electric motor on then dirty water from well will take its way to water tank passing through filter.
I can boil cooking/drinking water

If your filter is rated same as the flow rate of the pump then it will work in the system. However filters with this kind of flow rate do not remove small organizims etc, that is why water is also clorinated.

You should look at iodine treatment to kill the orgs in the water for temporary solution, it is less dangerous than chlorine for home use. But you can only do small quantities. I would not bath or clean with the water, you can have it tested to see whats really there.

How do you know the sewage line is leaking and causing the problem?

You should persue the people/government that own the sewer line that is leaking to fix the problem and even provide you a new well. You may need a lawyer if they wont listen.