Is ozonotherapy really effective for herniated disks?

Investigational. There are lots of investigational options out there for treatments such as ozonotherapy, methyl blue injections, stem cell therapies and homeopathic injections, prolotherapy, etc... Some of these have better results and also have more research going into them. Most if not all are not covered by insurance due to the investigational nature. I would consider stem cell therapy as an option overall.
No. There are no studies to show that ozone can heal or restore a herniated disc and relieve pain. Save yourself the trouble.