Premium
Fifteen Years of Offgas Transfer Efficiency Measurements on Fine‐Pore Aerators: Key Role of Sludge Age and Normalized Air Flux
Author(s) -
Rosso D.,
Iranpour R.,
Stenstrom M. K.
Publication year - 2005
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143005x41843
Subject(s) - aeration , diffuser (optics) , flux (metallurgy) , airflow , bubble , environmental engineering , air stripping , environmental science , secondary air injection , wastewater , chemistry , waste management , materials science , mechanics , metallurgy , thermodynamics , engineering , light source , physics , optics
Fine‐pore diffusers, often called fine‐bubble diffusers, have nearly replaced coarse bubble diffusers in municipal wastewater treatment over the past 20 years. The rapid increases in energy costs, which began in the 1970s, created financial incentives to upgrade to this more expensive and maintenance‐intensive method of aeration. Fine‐pore diffusers have the added benefit of reducing volatile organic compound stripping and reduced aeration heat loss. This paper summarizes 15 years of oxygen transfer efficiency measurements using the offgas technique. Efficiencies are shown for different types of diffusers at various tank geometries (depth, diffuser size, and number), airflow rates, and mean cell retention times (MCRT or sludge age). By normalizing the airflow rates per unit of depth and diffusing area, efficiencies measured in different plants can be compared. The results show that aeration efficiencies are logarithmically related to the ratio between MCRT and the normalized air flux, with transfer rates suppressed by low MCRT or high normalized air flux systems. There is no evidence for different α factors among the different types of fine‐bubble diffuser types.