By Mark Gehring, business development and market manager, biological treatment, Xylem Water Solutions and John Lindam, biological treatment process engineer, Xylem
On paper and in practice, aeration options and their corresponding efficiencies are calculated and compared.
Research and experiences within biological treatment have led to greater ability among municipal water resource recovery facilities to review and upgrade equipment and subsystems to reduce energy consumption. In most cases, processes and equipment involving aeration are the major consumers of energy. It has been estimated that up to 60 percent of a plant’s power consumption can be attributed to aerobic reactors in the activated sludge process of secondary treatment.
In this article, factors pertaining to power requirement and oxygen transfer of aeration systems in biological treatment are discussed, with emphasis on the difference and effects on energy efficiency between fine-bubble aeration and mechanical surface aerators. In particular, oxidation ditches are discussed; with numerous installations in the U.S. and worldwide, they present a number of engineering challenges with respect to aeration and mixing.