I am giving you information based on some research that I did for removing arsenic from water supplies in southeast Asia. I have not done anything related to household systems in the US.Originally Posted by sandpond
0.036 mg/liter is not a level that creates imminent danger, but I would fix it if it were my well and my kids.
Your choices depend on a number of things and you need a complete analysis of the water. Some of the systems for removing arsenic involve adsorbing it on precipitated iron and filtering out the iron. Therefore, the amount of iron in the water is a factor in using those systems.
There are two different forms of arsenic compounds (I'm away from my references but my recollection is that they are arsenite and arsenate) and some systems remove only arsenate.
There are systems that use iron deposited on a granular substrate such as alumina or other mineral, and the mineral is thrown away when ir reaches capacity. The regeneration process is usually not something that a homeowner wants to do (sodium hydroxide (lye) and hydrochloric acid).
Whatever solution you select, I suggest separating your potable water (drinking and cooking) from the other uses so you don't have to treat it all. Brushing your teeth with it isn't going to be a problem at the level you report. Washing vegetables or running the dishwasher is not going to be a problem.
If you treat only the potable water, then your total usage and total operating cost should be low. You should do a comparison of the cost of just buying water for drinking and cooking. You can do that while you make the decision on the system. Look at the cost of fairly large quantities; not what you get in single gallon jugs at the grocery store.
Take the time necessary to compare and carefully evaluate systems that someone wants to sell you, and get some guarantees on removal effectiveness and operating cost. I don't know what systems are being sold for indivuidual homes.
Your hardness is near the upper limit of what water suppliers consider acceptable. You might have to soften it if you install an RO system.