Abstract: A rotary distributor speed control system that uses hydraulic forces is provided. This rotary distributor speed control system is part of a trickling filter used in wastewater treatment. The trickling filter includes a tank which is filled with a porous filter media, a center column that extends through the center of the tank and holds a feed pipe through which influent wastewater flows, and distribution arms that extend radially from the center well. Each distribution arm has a forward side and a reverse side. The forward side and the reverse side each define at least one orifice. Slide gates are coupled with the distribution arms, and these gates can be moved so as to cover the orifices. A slide gate valve operator is also coupled with each arm for mechanically moving the slide gates in response to a change in influent feed flow, a change in arm speed, or external conditions.