C.H.
Having dealt with alot of biters in my class, I can say that it depends on the biter.
In this case is sounds as though he is biteing from either overstimulation or strong emotions he experiences from being around so many children.
No matter the motive, I usually suggest the parent set up playdates with children, increasing the number kids based off the child's progress. Your attention needs to be fully on him, without letting him know. So don't distract yourself by talking on the phone or making lunch or anything. What his emotions and see what is provoking the biting. Then start to correct his behavior by redirecting how to handle that emotion. For example. I had a biter that would do it when other children would take his toys or something he felt was his. So I redirect his emotion by showing him how to grunt and stomp his foot to show his was angry (he couldn't talk yet, otherwise I would have asked him to use word to say he was mad). Another child, for some odd reason was just totally obsessed with this little red headed girl, and kept doing anything to torture her, biting included. Because it was only her, we figured he was really interested in her, but didn't know how to express it. We had to spend an extensive amount of time showing him how to interact with her. he did get better, but I never stayed long enough to see it fully recover.
Anyway, just arrange playdates were he can be watched from a distance and see why he is biting, and redirect the emotion with an age appropiate responce. Increase the number of kids until he can handle the playgroup atmosphere better. It will take time. Just stick with it.