Is it possible to restrict person or group columns in a site collection to resolve only from one OU in AD?

I would like to create two site collections in a web application. These site collections are belonging to two different customers so I would like to make sure users belongs to one customer do not resolve users belong to other customer in their site collection at all.

I don’t want to create two different SharePoint servers for this purpose. One idea is, create two different Organizational Units in AD and add AD users in corresponding OU. But, is it possible to restrict person or group columns in a site collection to resolve only from one OU in AD? If yes, please suggest the steps. Otherwise, any other suggestions?

Thank You