Sewer Airflow Analysis: An Integral Part of Collection System Planning, Design, and Operation

Gravity sewers are designed for efficient collection and conveyance of wastewater flows. Conventional planning and design mostly overlook the importance of the airflow that takes place in the sewer above the water line (sewer headspace). While this practice may not result in noticeable problems in many cases, it can lead to extremely costly and troublesome operational problems in larger, more complex systems. This has been the case in a number of large systems including the City of Los Angeles (CA), Orange County Sanitation District (CA), and Clark County Water Reclamation District (NV), which are managing odor problems resulting from complex airflow dynamics. These agencies are adopting a comprehensive and systematic approach to managing the collection system odors and are benefiting from recent advances in airflow modeling and analysis pioneered in the City of Los Angeles. Increasingly, wastewater agencies are realizing the importance of airflow in sewers and the requirement for comprehensive sewer airflow analysis and management as an integral part of collection system planning, design, and operation.