As others have ...

As others have noted/suggested, Aeration & Chlorination are the standard/basic Rx methods of removal: But for Chlorination to work properly, treated water needs to be held - in a pipe or enclosed area - long enough for the chem process to fully interact. Aeration of Bore Hole water could prove both technically & cost difficult; with results depending on extent/source of the H2S tainting. To reinforce other recommendations, you REALLY need to try to determine the natural causal source of this chemical: E.g., in deepening the bore holes, you may have hit some volcanic rock formations. Grasses/weeds can also be a source; but whatever, there's a bacterial factor in the mix. Cautionary Note: "Chlorine" use is the "default" antidote; but this chem has been used for pathogenic "purification" purposes for over half a century now. However, what those "hooked" on this so-called panacea are totally ignoring are these now well known facts: 1) Chlorine is now a well known/recognized CARCINOGEN, with extended/heavy use!; 2) It's ingestion can also cause a number of potentially very negative health side-effects, with even short-term use; some people being HIGHLY sensitive! (NB: I've personally witnessed people go into convulsions, after ingesting heavily chlorine treated "raw" water.); 3) Chlorine has a very short "shelf/use life", & thereby easily loses whatever bacteria conversion/elimination powers it has at full strength. Bottom Line: You first need to determine the causative source creating the H2S condition/problem. Just keep in mind, as you review/consider all those "chemistry" change suggestions/formulae posted above: When one starts mixing chemicals, it's easy to arrive at "unanticipated/unwanted" results: INCLUDING THE CREATION OF POISONOUS/EXPLOSIVE GASES & WATER!!