Yes, UV light would be more effective than chlorination at killing most of this stuff. But, you know...good luck convincing people to add expensive UV systems to their sewage effluent.
Apparently there is anyway movement to UV, as it is safer than handling/dealing with chlorine (at least, this is what someone tells me about the industry in the US).
UV is certainly easier to deploy than chlorine gas (a UV leak won't poison everyone in the room via gas inhalation), but it's still dangerous at the scales used to sterilize large quantities of water.
The bigger problem than either is that AFAIK, few places bother to sterilize their effluent. I'm not even sure if San Francisco bothers to do that, actually...
UV is used in some wastewater reclamation plants, it is the new how shit as of about 10 years ago. But with all things the volume of water being treated determines which processes are used, I know of a UV only plant that processes 37million gallons a day via UV. Thirty minutes away at a larger facility that treats 150million gallons a day they use chlorine only. These are massive facilities, and to change the processes used is a massive undertaking, expecting them to be able to pivot over night is not realistic.
New Scientist has an article in this weeks number about sunshine and fresh air working as "antibiotics", and how the use of air and light could reduce the risk of infections in hospitals.