Estimating the Effect of Magnetite on Nitrogen and Phosphorus Removal Using Intervention Analysis

Abstract

This study investigated the effectiveness of magnetite as ballast material through a technology called BioMag in nitrogen and phosphorus removal and in processing peak flows at a wastewater treatment plant using data from the Marlay-Taylor Water Reclamation Facility in Maryland. Using intervention analysis, the magnitude of the difference in effluent total nitrogen (TN) and total phosphorus (TP) before and after the magnetite technology retrofit was estimated, but with the time series forecast forward both before and after the upgrade, as opposed to a backward forecast of the series after the upgrade suggested by previous studies. The sludge volume index (SVI) and mixed liquor suspended solids (MLSS) were also examined to ascertain the effect of the magnetite technology on these parameters. The findings showed improved SVI and increased MLSS and that the upgraded facility is successfully treating peak flows while maintaining good effluent quality. The effluent TN and TP decreased by 98% and 77%, respectively. These results were compared to results from a backward forecast as well as results obtained from a simple difference between actual reported values.