Monitoring the performance of waste water treatment aerators
Dudley, J., WRc
(free)
Abstract
The conventional way to estimate the performance of an operational aerator is onerous. The process involves isolating the aerator from incoming flow; switching the aerator off briefly to allow the dissolved oxygen levels to fall; restarting the aerator; and, monitoring the rate of dissolved oxygen increase to estimate the mass transfer rate of the aerator, and from that the aeration efficiency. A Kalman filter is a technique for estimating the aerator performance in situ, without the need for isolating the tank or changing operational settings. The filter provides estimates of the respiration rate and oxygen transfer rate. If there are additional power measurements then the aeration efficiency can also be estimated. The technique was evaluated at four wastewater treatment plants, with the results compared against conventional reaeration tests. The direct measurement of bubble sizes provides additional information on performance that the filter approach can miss. A new measuring approach for the UK water industry (using an instrument developed for use in the nuclear sector) was evaluated at the same four sites, and found to detect differences between parallel lanes that were not immediately obvious from the filter technique because of the range of variation in aeration performance found with varying flows, loads, and the application of DO control.
