Predictive control of wastewater treatment plants as energy-autonomous water resource recovery facilities

TL;DR

This paper introduces an automatic control method for wastewater treatment plants to operate as energy-autonomous resource recovery facilities, ensuring water quality and biogas production through model predictive control.

Contribution

It presents a novel output-feedback model predictive control approach for optimizing water quality and energy self-sufficiency in full-scale wastewater treatment plants.

Findings

Successful long-term operation with energy-neutral biogas production

Control strategy accommodates diverse resource recovery goals

Proof-of-concept demonstrated on a full-scale plant

Abstract

This work proposes an automatic control solution for the operation of conventional wastewater treatment plants (WWTPs) as energy-autonomous water resource recovery facilities. We first conceptualize a classification of the quality of treated water for three resource recovery applications (environmental, industrial, and agricultural water reuse). We then present an output-feedback model predictive controller (Output MPC) that operates a plant to produce water of specific quality class, while also producing sufficient biogas to ensure nonpositive energy costs. The controller is demonstrated in the long-term operation of a full-scale WWTP subjected to typical influent loads and periodically changing quality targets. Our results provide a proof-of-concept on the energy-autonomous operation of existing wastewater treatment infrastructure with control strategies that are general enough to accommodate a wide range of resource recovery objectives.