Public defence in Chemical Engineering, M.Sc. Otacílio Bezerra Leite Neto

Title of the thesis: Advances in predictive control and feedback equilibrium-seeking with applications to autonomous water resource recovery

Thesis defender: Otacílio Bezerra Leite Neto
Opponent: Prof. Lorenz Biegler, Carnegie Mellon University, United States
Custos: Prof. Iiro Harjunkoski, Aalto University School of Chemical Engineering

A paradigm shift is underway: Wastewater, historically viewed as an environmental hazard, is now recognized as a sustainable source of clean water, energy, and nutrients. Under this context, wastewater treatment plants (WWTPs) are being rethought as water resource recovery facilities (WRRFs), plants that produce goods and energy using wastewater as a raw material. While current efforts focus on designing novel processes, this dissertation considers the role of automatic decision-making (that is, feedback control) in this transition instead. We propose two research directions: (i) The repurposing of already existing infrastructure to these emerging objectives, and (ii) The promotion of a wastewater-centered market through an interconnected network of WRRFs.

In the first direction, the thesis studies the predictive control of conventional biological WWTPs for water resource recovery tasks. The framework is designed to control a WWTP to recover nutrients directly into effluent streams, thus producing reused water of tailored quality, while ensuring that such an operation regime can be fully sustained by the energy recovered from processing sludge into biogas. In the second direction, the thesis studies the control of (noncooperative) multi-agent systems. The underlying idea is to connect WRRFs into a supply chain exchanging wastewater and recovered resources. Here, the contribution is theoretical: it addresses the open problem of seeking game-theoretical equilibria (e.g., the Nash equilibrium) of output-feedback policies that incorporate both operational and informational constraints. The thesis proposes novel equilibrium-seeking algorithms in which noncooperative agents are able to converge to an equilibrium of feedback policies, while simultaneously operating their subsystem under the aforementioned constraints. 

Our theoretical and experimental findings contribute a step towards the transition into zero-waste water resource recovery infrastructures. In turn, the contributions to multi-agent control should benefit applications in different domains, such as smart grids and supply chain management.

Keywords: water resource recovery, feedback control, model predictive control, moving horizon estimation, multi-agent systems, Nash equilibrium, system level synthesis, fixed point iteration

Thesis available for public display 7 days prior to the defence at Aaltodoc. 

Contact information: 
otacilio.neto@aalto.fi