A disc filter having a controller for controlling or minimizing effluent surges is provided. The disc filter is operative to carry out a method or process for controlling the flow of effluent produced by the disc filter. The basic method entails sensing one or more process variables that are a function of the effluent, and based at least in part on the sensed process variables, the disc filter controls the flow of the effluent by implementing various control functions such as: 1) rotating the rotary filter discs of the disc filter one revolution or less without backwashing; 2) rotating the rotary filter discs more than one revolution at a relatively slow speed without backwashing; 3) rotating the rotary filter discs for one revolution or more at a relatively slow speed while backwashing; 4) rotating the rotary filter discs at a relatively high speed with or without backwashing; and 5) rotating the filter discs one revolution or more and periodically backwashing.