Suitability of A Biofilter For Removing VOCs

yes, many things are inert and persist.

http://www.google.ca/search?hl=en&q=dnapl&btnG=Google+Search&meta=

"Are there VOCs that cannot be biodegraded in a biofilter? I presume that some bacterias can only biodegrade certain chemicals but not a wide variety of chemicals. Some chemicals could even be a "poison" to some bacterias."

Yes, many of the non-biodegradable VOCs are of the halogenated type . Also, certain other VOCs (e.g. phenols) are toxic to many types of bacteria and require an extended anerobic treatment process to degrade them.

"If different types of bacteria cultures is needed to biodegrade a group of VOCs, can these different cultures live together?"

No, some are aerobic (i.e. require dissolved oxygen) and some are anerobic. Even different species of aerobic and anerobic bacteria cannot always live together. Bacteria secrete antibiotics (it's how pharmaceutical firms manufacture these things) to kill off the competition. Only bacteria that can tolerate the same conditions and do not compete with one another can live together.

"Where can I find information about VOCs that can and cannot be biodegraded?"

Try Google. You can find a lot of information here. Also, if you have access to them, professional journals are also a great source of information.