Effect of anaerobic and anoxic selectors on oxygen transfer in wastewater

Pilot- and full-scale systems were operated with and without anaerobic and anoxic selectors to determine the effect of selectors on fine pore diffuser oxygen-transfer efficiency as reflected by the alpha correction factor. Al l systems operated at a mean cell residence time between 7.0 and 10.0 days and were fully nitrifying. Process water oxygen-transfer performance was mo nitored using offgas tests. Average measured alpha (alpha) factors in the p ilot plant ranged from 0.33 to 0.53 without selectors in operation and from 0.39 to 0.51 with selectors in operation. Average measured alpha factors i n the full-scale plant ranged from 0.29 to 0.79 without selectors in operat ion and from 0.28 to 0.68 with selectors in operation. Both pilot- and full -scale tests indicated that selectors had little influence on oxygen-transf er efficiency as reflected by a when compared with systems that were fully nitrifying.