Energy-environment closed-loop through Oxygen Pinch

Abstract

Oxygen Pinch emphasizes oxygen management and integration by splitting and recycling of oxygen/substrate requiring processes to achieve minimum “fresh” oxygen supply and maximum biodegradation per unit mass and hence to reduce energy consumption, to shorten operating times and to improve plant capacity. The presented approach considers not only the concentration differences that represent the mass transfer driving force between streams of varying substrate concentration but also the influence substrate utilization kinetics have on this driving force. Through the use of classical Pinch Principles, the maximum amount of substrate required to maintain a healthy sludge is identified assuming oxygen concentration is not limiting. The challenge posed by the presented case study towards improvement of an existing plant is not to reduce the oxygen supply (the oxygen is always maintained in excess), but to improve the substrate utilization for the same amount of supplied oxygen thereby increasing the capacity of the plant and lowering the energy consumption per unit volume of wastewater. It is reported that the principles introduced by the Thermal Pinch concept can work successfully for environment protection purposes and finally can again be returned to their original address leading to energy saving.