Aerobic–Anaerobic Microbial Wastewater Transformations and Re‐aeration in an Air‐Injected Pressure Sewer

Abstract

Wastewater quality changes and re‐aeration during transport in an air‐injected pressure sewer (force main) were studied. Samples were taken from an air‐injected pressure sewer located in the northern part of Japan. The study focused on the transformations of wastewater organic matter as characterized by measurements of oxygen uptake rate. Wastewater was maintained under aerobic conditions by injecting air, which controlled sulfide formation and removed readily biodegradable substrate ( S S ) by aerobic microbial processes. To preserve S S , it was necessary to decrease dissolved oxygen concentration by reducing air‐injection flow rate. An aerobic–anaerobic wastewater process model for the air‐injected pressure sewer was established, and model parameters were determined based on experimental findings. It was possible to simulate transformations of wastewater organic matter, dissolved oxygen, and sulfide. The model can be applied to determine an appropriate air‐injection flow rate to control sulfide formation and reduce S S removal.