Theory to Practice: Oxygen Transfer and the New ASCE Standard Michael K. Stenstrom, Shao-Yuan (Ben) Leu, and Pan Jiang Civil and Environmental Engineering Dept, UCLA, Los Angeles, CA ABSTRACT Oxygen transfer is an important part of wastewater treatment and accounts for as much as 60% of the energy consumption for the activated sludge process. Prior to 1984, no standard method for quantifying oxygen transfer existed, which created problems in the design and warranties for treatment plants. The ASCE Standard for the Measurement of Oxygen Transfer in Clean Water and the ASCE Standard Guidelines for In-Process Oxygen Transfer Testing have found widespread application and have reduced the variability in new designs and allowed operators and engineers to access the process operation of existing treatment plants. A new clean water standard is in press as of this writing and the in-process Guidelines are undergoing updating for reissue. This paper illustrates the key concepts of both the Standard and the Guidelines and shows why they are important and reduced the variability of testing. The paper also highlights key new areas of the revised clean water Standard, which includes an optional correction for test water total dissolved solids concentration, and applications to loop (ditch) activated sludge process and the high purity oxygen activated sludge process. KEYWORDS Activated sludge, aeration, ASCE, off-gas, oxygen transfer, standard INTRODUCTION In 1977, under the sponsorship of the US EPA, a Committee organized by ASCE began the study of methods to quantify oxygen transfer rates in wastewater treatment. The Committee met as a group in Asilomar, California in 1978 (US EPA, 1979) and proposed consensus methods for establishing uniform and repeatable test conditions, estimating clean water parameters (mass transfer coefficient or K L A, and equilibrium oxygen concentration * ∞ C ) from reaeration data, and translating clean water rates to process conditions. The resulting methods were evaluated over next several years by the committee members, consultants and manufactures and refined through the collective experience of the group. The final result was the 1984 version of the ASCE Standard for the Measurement of Oxygen Transfer in Clean Water. The Standard was subsequently improved, updated and republished in 1991 and will be published again in 2006. Following the development of the Clean Water Standard, it was realized that the next most important gap in knowledge was the characterization of process water transfer rates. The Standard provided ways of calculating expected process water rates from clean water rates, by adjusting for standard conditions, such as barometric pressure, temperature and the effects of the contaminants in the process water (α and β factors for K L A and * ∞ C , respectively), but there were no consensus-based process water 4838 WEFTEC®.06 Copyright 2006 Water Environment Foundation. All Rights Reserved ©