The present technology relates generally to fluid filtration systems. In particular, several embodiments are directed toward compartmentally expandable rotating belt filters and associated systems and methods. In some embodiments, for example, a filtering system for contaminated fluid includes a first fluid filtering chamber having a first filter belt movably positioned therein and a second fluid filtering chamber having a second filter belt movably positioned therein. The first filter belt can be operable in parallel with the second filter belt. The system can further include a sensor configured to sense a condition related a volume of the contaminated fluid, a speed of flow of the contaminated fluid, or a level of contaminants in the contaminated fluid. A controller can be configured to initiate, stop, or adjust fluid flow to the first fluid filtering chamber and second fluid filtering chamber individually in response to the sensed condition.