First of all, you need to ...

First of all, you need to consider the survey of the area(borehole). Depth of 25m can get polluted easily, by activities such as latrine, graveyard, chicken farm and other types of compost and manure.

Again consider the following:

1. The history of Borehole (How long does it used),

2. Surrounding activities of the borehole,

3. Volume of water abstraction v/s population, and

4. Leaking sewer pipes and any illegal actives around the borehole.

Treating methods

Pressure process, is the best technology to remove the odour into the water, by using lime as buffer and Aluminium sulphate as indicator. Meaning two chemical are flocculants.  

Thank you,

Mr Mangena P