The market share of biofilm based wastewater treatment systems has largely remained unchanged in the US over the last thirty years, while the market share for activated sludge systems has markedly increased. One of the reasons for the static market share of the former is the lack of sufficient research to support practical models useful to designers. A recent positive development is the inclusion of biofilm process elements in whole plant simulators. It is the obligation of a design consultant to evaluate the details of incorporated models prior to their adoption for design. Identified deficiencies are described and recommendations are offered for research to support model improvements. The US market share for biofilm reactors can be improved by additional research, by enhancing the transparency of mechanistic bases of biofilm reactor systems, and by translating innovations from older technologies. New technologies are certain to arrive as investigators are increasingly recognizing that biofilm environments can be induced to be quite different than activated sludge floc environments, giving them a broader potential for capability development.