A plant wide aqueous phase chemistry model describing pH variations and ion speciation/pairing in wastewater treatment process models

There is a growing interest within the Wastewater Treatment Plant (WWTP) modelling community to correctly describe physico–chemical processes after many years of mainly focusing on biokinetics. Indeed, future modelling needs, such as a plant-wide phosphorus (P) description, require a major, but unavoidable, additional degree of complexity when representing cationic/anionic behaviour in Activated Sludge (AS)/Anaerobic Digestion (AD) systems. In this paper, a plant-wide aqueous phase chemistry module describing pH variations plus ion speciation/pairing is presented and interfaced with industry standard models. The module accounts for extensive consideration of non-ideality, including ion activities instead of molar concentrations and complex ion pairing. The general equilibria are formulated as a set of Differential Algebraic Equations (DAEs) instead of Ordinary Differential Equations (ODEs) in order to reduce the overall stiffness of the system, thereby enhancing simulation speed. Additionally, a multi-dimensional version of the Newton–Raphson algorithm is applied to handle the existing multiple algebraic inter-dependencies. The latter is reinforced with the Simulated Annealing method to increase the robustness of the solver making the system not so dependant of the initial conditions. Simulation results show pH predictions when describing Biological Nutrient Removal (BNR) by the activated sludge models (ASM) 1, 2d and 3 comparing the performance of a nitrogen removal (WWTP1) and a combined nitrogen and phosphorus removal (WWTP2) treatment plant configuration under different anaerobic/anoxic/aerobic conditions. The same framework is implemented in the Benchmark Simulation Model No. 2 (BSM2) version of the Anaerobic Digestion Model No. 1 (ADM1) (WWTP3) as well, predicting pH values at different cationic/anionic loads. In this way, the general applicability/flexibility of the proposed approach is demonstrated, by implementing the aqueous phase chemistry module in some of the most frequently used WWTP process simulation models. Finally, it is shown how traditional wastewater modelling studies can be complemented with a rigorous description of aqueous phase and ion chemistry (pH, speciation, complexation)

Development of a fast and flexible generic process for the reduction of nitro compounds

The hydrogenation of aromatic nitro substrates is a frequently used reaction in the multi-step fabrication of active pharmaceutical ingredients (APIs). Today most pharmaceutical production processes are performed in batch mode. In the frame of the C2-campaign speed is an important factor during the production of a multitude of possible API’s. A generic reactor set-up able to be adapted for the transformation of a specific substrate would reduce the development time and thereby the campaign time significantly. In the frame of the EU-project F3-Factory such a flexible and continuous reaction system for this important reaction class able to produce 1-5 kg API is being developed. To allow for an easy and fast adaptation of this process for a range of nitro substrates a substrates adoption methodology (SAM) is also being developed. A literature study of the nature of different reduction methods (H2 gas, H-Donor, CO gas, etc.) led to the conclusion that the liquid phase reduction of aromatic nitro substrates by either hydrogen gas or an H-donor is the most selective method. Following the requirements of that reaction type a flexible and modular reactor for the liquid phase reduction with a heterogeneous slurry catalyst was designed that can be adapted for reduction of a range of nitro compounds. The generic process provides the possibilities of swapping out a reactor or work up technology as required. The equipments of the generic process should be also able to operate at wider range of operational variables making it suitable for a range of substrates. The SAM identifies the necessary changes to a generic process and plant in order to adapt it for a given substrate. The objectives of this presentation is to highlight the design of a generic nitro reduction process and to demonstrate the application of this generic process on a pharmaceutical manufacturing case study involving the nitro reduction of 6-Nitroquinoline