Purification methods for borewell water contaminated with sewage

The borewell water in our flats seems to have been contaminated with sewage water. Our flats is equipped with a septic tank and an additional soak pit to take care of additional flow of sewage water. Recently we added one more soak pit, which was almost near our borewell (approx. 5 to 7 feet difference betwn the new soak pit and the borewell). Over a period of time the water quality seems to have deteriorated and very recently we realised that the borewell water is contaminated. The water color is normal but we get strong smell of sewage water. Could you please suggest what we can do to overcome from this problem. Are there any viable means to treat this water and make it potable (or atleast make it safe for washing and bathing)?

Note: I have read through the question that was earlier answered on this service also regarding sewage in well water and found that to be an eye-opener. We are actually looking at some of those suggestions. But my immediate concern was to make the current water through the borewell more potable. It is not a big apartment complex, so we cannot invest on a very high-end water purification plant. Is there a simple way by which I as an individual flat-owner do to filter the current water and make it more potable (atleast for bathing and washing)? Your thoughts on this would be much appreciated.