My intuition as someone who has a UV light on their drinking water is also that the blood would also be too opaque for direct irradiation, anyway. (You need to

My intuition as someone who has a UV light on their drinking water is also that the blood would also be too opaque for direct irradiation, anyway. (You need to filter your water before it hits the UV light, because if it is eg cloudy or has too many minerals in it, the water treatment salesman tells me, the UV light won't actually do anything.)