Relationship Between Oxygen Transfer Rate and Airflow for Fine‐Pore Aeration Under Process Conditions

Abstract

Although feedback systems that control the air supply to aeration tanks inherently incorporate some assumption about oxygen transfer response to changes in airflow, it is rare to measure this relationship under process conditions. This paper reports measurements of oxygen mass-transfer curves (MTCs) for a tank at the Tillman Water Reclamation Plant in Los Angeles, California. The curves were obtained by measuring the oxygen transfer efficiency (OTE) at selected points for several set values of airflow while the plant was operating. They approximate inverted parabolas because increasing the airflow increases the amount of oxygen supplied by the blowers, but decreases the OTE, which is the fraction of the supplied oxygen that actually enters the water. Data were recorded from both recently cleaned diffusers and ones that were moderately to severely fouled.The peaks in the curves from the fouled diffusers are at or below the midpoints of the observed ranges of airflows. Hence, there is only a narrow range of usable airflows between the lower limit, determined by the manufacturer of the diffusers, and the peak of the MTC, which is the maximum amount of oxygen that can be supplied. The peaks for the cleaned diffusers are higher, which allows more ability to adjust to changing biological loads.These results show that existing dissolved oxygen control systems may not be adequate and that fouling may reduce not only the overall efficiency of an aeration system but its ability to respond to changes in the biological load. The measurements also provide some insight to the limitations of using sparsely distributed dissolved oxygen sensors to control the aeration process and the excess costs that are incurred by the consequent need to compensate for uncertainty with extra air. However, additional testing is needed to determine whether the present results are aberrant or typical of tanks with fouled or cleaned diffusers. Water Environ. Res., 73, 266 (2001).

Fifteen Years of Offgas Transfer Efficiency Measurements on Fine‐Pore Aerators: Key Role of Sludge Age and Normalized Air Flux

“…With fine‐pore diffusers, the efficiency is also affected by the condition and age of the diffusers ( Iranpour et al, 2000a and b , 2001 , 2002 ). Membrane diffusers can harden or soften after use, resulting in increased pressure loss or increased bubble diameter.…”

Application of jetventurimixer for developing low-energy-demand and highly efficient aeration process of wastewater treatment

“…OTE, as assessed for air transfer to sustain microbial respiration, is closely related to overall energy demand and subsequent sustainability of the process [ 19 ]. OTE is the percentage of supplied oxygen that actually enters the water [ 20 ]. To calculate OTE of the JVM and air diffuser aerator, the following Eq.…”