Which of the following tasks does not belong to a chemical engineer project?

The task that does not belong to a chemical engineering project is the one involving figuring out how to communicate via Bluetooth. This task is primarily associated with electrical engineering and computer science, focusing on communication systems and networking technology.

In contrast, the other tasks are intrinsic to the chemical engineering field. Building chemical reactors involves designing and constructing systems where chemical reactions take place, which is a fundamental responsibility of a chemical engineer. Designing wastewater treatment systems requires an understanding of chemical processes to purify water, an essential aspect of environmental engineering within the chemical field. Developing catalysts for fuel cells is related to creating substances that speed up chemical reactions, particularly in energy production, which aligns with chemical engineering's focus on reaction mechanisms and product efficiency.

Thus, the inclusion of Bluetooth communication is distinctly outside the scope of chemical engineering principles and practices.