What do you need? Why?
When approaching the issue of treatment, I find the second question the most important. So many people have an interesting response when I ask why they have the treatment unit they do. It usually goes along the lines of, "someone told me I needed it." or "it was there." or "just in case." The number of educated consumers of treatment units is minimal. A number of years ago there was a company (no longer operating in Connecticut because Consumer protection chased them out) who would scare a home owner because of all the potential problems they might have and sell them a unit that this company made that had no chance of fixing the problems that were true to that well. The reality, most well water is very good and healthy.
Okay so lets deal with the most prevalent issue, aggressive water. You might get a hint that you have this problem if you see blue-green staining in the white porcelain fixtures. If you do not notice that, you will notice when your water pipes develop small pinhole leaks and plumbers have to be called. Treatment depends on the water quality and if the water is the cause. The pH is one issue and levels below 6.4 (7 is neutral) might be an issue. I say might because if your water hardness is about 150 mg/L, the calcium will coat the pipes and prevent the acid from hurting them. So figuring out the aggressive index of the water is important. The simplest treatment is a calcium carbonate bed (marble chips) and it will raise the pH modestly and add hardness to the water, all very good. Sometimes this does not do the trick or is not applicable because either the pH is below 6 and/or there is a significant amount of hardness in the water already. In this case a feeder pump must be installed to sodium or potassium hydroxide. Those substances are dangerous and so the water should be monitored.
If the water is not the problem for the blue staining, you will need to call an electrician who knows what electrolysis is. This can be an expensive proposition, but the fix is usually fairly simple, ground the copper pipes.
Again, the first step is have your water tested by a state certified lab, then go on with it.