Module consists of four constant rate filters with individual feed pumps, and five chemical pumps. Each filter is independent with automatic flow control. The air scour and backwash systems are shared by all filters, and also utilize automatic PID flow control. Chemical feed pumps are flow paced with direct entry of chemical dosage. Each chemical pump can be selectively paced to any of the filter feed flows, the combined filter feed flow, or the backwash flow. An improved backwash process is included, providing superior performance when operating biological filtration processes. Backwashing is automatic, and initiated manually by an operator in the manual mode, or on runtime, run volume, headloss, or effluent turbidity in the automatic mode. Only one filter may be backwashed at a time. Other features include automatic data logging of key parameters, remote monitoring and control using a standard web browser, and email alarm notification.