Development of a MATLAB based model for the biological water processor of the water recovery system of an advanced life support program

The water recovery system (WRS) is one of the necessary systems of an advanced life support (ALS) program that regenerates potable water by sequentially processing wastewater through its four subsystems. The biological water processor (BWP) is one of the complex subsystems of a WRS that involves processes described by both continuous time dynamics as well as discrete event dynamics. It consists of two reactors, the organic carbon oxidation reactor and the nitrification reactor, where wastewater is treated and then it is stored in a gas-liquid separator. A part of the stored water is recycled back to the first reactor and the remaining water is fed to the next subsection for further processing. In this paper, wastewater flow through an organic carbon oxidation reactor and a nitrification reactor is analyzed and the dynamics of the gas-liquid separator are studied. The state variables of the BWP are identified and distributed models are developed for each unit of BWP. Further, these distributed models are integrated and the dynamics of the BWP is studied as a complete subsystem. The state variables description of the subsystem is simulated using MATLAB/Simulink.