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An Alternative Mathematical Model for Oxygen Transfer Evaluation in Clean Water
Energy consumption from aeration system is a biggest part of the total energy cost in wastewater treatment plant and account for as much as 60% of the energy consumption for the activated sludge process. Therefore, it is very important to know how effective the aeration system and significant attention has been paid to development and upgrade of standard method for quantifying oxygen transfer efficiency of the aeration system. In order to evaluate the performance of different types of aeration systems, the American Society of Civil Engineers (ASCE) and US EPA jointly developed a standard for the measurement of oxygen transfer in Clean Water in 1984. The Standard was subsequently improved, updated, and republished in 1991 and 2006. The focus of this paper has been to develop an alternative model which includes more parameters than the standard method. A new model would probably be a more accurate description of the aeration process and give more reliable oxygen transfer performance evaluation results.
BOD5 REMOVALS VIA BIOLOGICAL CONTACT AND BALLASTED CLARIFICATION FOR WET WEATHER
Ballasted clarification has long been accepted as a viable treatment method for the removal of solids (TSS) from wet weather wastewater flows. However, as there is no biological mechanism in a typical system, removal of Soluble BOD5 is minimal and total BOD5 removal is therefore a function of the Total BOD5 present as particulate. The addition of an aerated contact tank upstream of the ballasted clarification unit, where wet weather wastewater and Return Activated Sludge (RAS) are combined, has been proposed as a means to accomplish Soluble BOD5 (SBOD5) uptake and meet the EPA's requirement of 85% Total BOD5 removal for secondary treatment.