Feasibility of hydraulic separation in a novel anaerobic-anoxic upflow reactor for biological nutrient removal

ABSTRACT : This contribution deals with a novel anaerobic-anoxic reactor for biological nutrient removal (BNR) from wastewater, termed AnoxAn. In the AnoxAn reactor, the anaerobic and anoxic zones for phosphate removal and denitrification are integrated in a single continuous upflow sludge blanket reactor, aiming at high compactness and efficiency. Its application is envisaged in those cases where retrofitting of existing wastewater treatment plants for BNR, or the construction of new ones, is limited by the available surface area. The environmental conditions are vertically divided up inside the reactor with the anaerobic zone at the bottom and the anoxic zone above. The capability of the AnoxAn configuration to establish two hydraulically separated zones inside the single reactor was assessed by means of hydraulic characterization experiments and model simulations. Residence time distribution (RTD) experiments in clean water were performed in a bench-scale (48.4 L) AnoxAn prototype. The required hydraulic separation between the anaerobic and anoxic zones, as well as adequate mixing in the individual zones, was obtained through selected mixing devices. The observed behaviour was described by a hydraulic model consisting of continuous stirred tank reactors and plug-flow reactors. The impact of the denitrification process in the anoxic zone on the hydraulic separation was subsequently evaluated through model simulations. The desired hydraulic behaviour proved feasible, involving little mixing between the anaerobic and anoxic zones (mixing flowrate 40.2% of influent flowrate) and negligible nitrate concentration in the anaerobic zone (less than 0.1 mgN L-1) when denitrification was considered

Green Pathways for the Enzymatic Synthesis of Furan-Based Polyesters and Polyamides

The attention towards the utilization of sustainable feedstocks for polymer synthesis has grown exponentially in recent years. One of the spotlighted monomers derived from renewable resources is 2,5-furandicarboxylic acid (FDCA), one of the most promising bio-based monomers, due to its resemblance to petroleum-based terephthalic acid. Very interesting synthetic routes using this monomer have been reported in the last two decades. Combining the use of bio-based monomers and non-toxic chemicals via enzymatic polymerizations can lead to a robust and favorable approach towards a greener technology of bio-based polymer production. In this chapter, a brief introduction to FDCA-based monomers and enzymatic polymerizations is given, particularly focusing on furan-based polymers and their polymerization. In addition, an outline of the recent developments in the field of enzymatic polymerizations is discussed. </p

Mode switching control in stages with synchronized motion

During the chuck swap process of a wafer scanner, i.e. the exchange of the measured chuck with the exposed chuck, a control mode switch occurs between two measurement systems. As a result of this switch, unwanted transients occur in the wafer stage system: the long-stroke (LoS) and the short-stroke (SS) wafer stage modules. By means of initial value compensation, an impulsive force is used to counteract these transients. But in view of actuator limitations, this appears insufficient and the following solution is proposed. Upon occurrence of a mode switch, the setpoint is adjusted with a third-order profile that limits the required actuator forces by limiting the jerk levels. The profile is scaled with the velocity difference measured over the mode switch. As a result, a continuous and smooth transition of the position signals is obtained. In addition, the SS feedforward controller is replaced by a feedback term in the multivariable and synchronized wafer stage system. This removes the interaction term from the LoS to the SS module, which decouples the synchronization performance from mode switching, and which renders the control design multi-loop SISO

Oblique Projected Dynamical Systems and Incremental Stability Under State Constraints

Projected dynamical systems (PDS) are discontinuous dynamical systems obtained by projecting a vector field on the tangent cone of a given constraint set. As such, PDS provide a convenient formalism to model constrained dynamical systems. When dealing with vector fields, which satisfy certain monotonicity properties, but not necessarily with respect to usual Euclidean norm, the resulting PDS does not necessarily inherit this monotonicity, as we will show. However, we demonstrate that if the projection is carried out with respect to a well-chosen norm, then the resulting 'oblique PDS' preserves the monotonicity of the unconstrained dynamics. This feature is especially desirable as monotonicity allows to guarantee important (incremental) stability properties and stability of periodic solutions (under periodic excitation). These properties can now be guaranteed based on the unconstrained dynamics using 'smart' projection instead of having to carry out a difficult a posteriori analysis on a constrained discontinuous dynamical system. To illustrate this, an application in the context of observer re-design is presented, which guarantees that the state estimate lies in the same state set as the observed state trajectory

Industry engagement with control research: Perspective and messages

Despite the enormous benefit that has accrued to society from control technology and the continued vitality of control science as a research field, there is broad consensus that the practitioners of control and the academic research community are insufficiently engaged with each other. We explore this concern with reference to the oft-cited theory/practice gap but also from an industry perspective. The core of this article is comprised of ten “messages,” intended primarily for researchers interested in the practical impact of their work, that we hope shed insight on the industry mindset. Results from surveys and other data are cited to underpin the points. Some educational synergies between industry and academia are also noted. To highlight the continuing relevance of control science to industry, several recent examples of successful, deployed advanced control solutions are presented. The authors of this article are members of the IFAC Industry Committee, formally established in 2017 with objectives that include (per the updated IFAC Constitution) “increasing industry participation in and impact from IFAC activities.