Control of Anaerobic Digestion Process

The anaerobic digester is a common biological wastewater treatment process. A recently proposed fifth-order, nonlinear, dynamic model for the anaerobic digester has been shown to be qualitatively correct. Three methods of controlling the anaerobic digester are considered: base addition, organism recycle, and flow control. Feedback and feedforward controllers are designed for each of the control mechanisms, and a discrete adaptive predictive flow control algorithm is proposed. The control studies indicate that feedforward base addition control, in response to organic loading, is more effective and less expensive than feedback proportional base addition control. The predictive controller periodically computes optimum influent flow rate to the digester based on model response. This direct digital control method is adaptable to other wastewater treatment processes and offers flexible control objectives, allowing operational costs and quality of performance to be assigned weight factors, based on operational goals.