 Figure 1: Prototype bioreactors I and II in full operation. In prototype I (left), the adult chamber is the large chamber on the right side of the reactor. In prototype II (right), the adult chamber is smaller and on the left of the reactor. The airlift column on the left side of prototype I is notably connected to the adult chamber by two openings in the wall separating the airlift column from the adults (more visible in Figure 2), whereas in prototype II the airlift column is completely surrounded by four walls. 