As others have said, ammonia in your tap water is not a good thing. Not even for humans. So I would call your local water authorities (as others have mentioned) and explain to them that you are seeing fairly concentrated amounts of ammonia in your tap water and that you'd like to know "why" and "if thats part of the filtration system".
...I can tell you right now, it shouldn't be part of filtering the water, however you need to investigate and see what they say. They do have an obligation to provide you with clean (safe) water.
...I can tell you right now, it shouldn't be part of filtering the water, however you need to investigate and see what they say. They do have an obligation to provide you with clean (safe) water.