Molecular and Kinetic Characterization of Anammox Bacteria Enrichments and Determination of the Suitability of Anammox for Landfill Leachate Treatment

Graduation date: 2017Anaerobic ammonium oxidation (anammox) has recently appeared as a\ud promising approach for removing nitrogen from landfill leachates because it requires\ud less oxygen and no organic carbon compared to traditional nitrification-denitrification\ud system, and it produces low sludge volumes, thereby reducing operating and\ud biological sludge disposal costs by over 60%. Anammox bacteria anaerobically oxidize\ud ammonia with nitrite to form dinitrogen gas, which is bubbled out of the system.\ud When combined with partial nitrification (the aerobic oxidation of half the ammonia\ud to nitrite), anammox bacteria can be an efficient and sustainable solution to treat\ud landfill leachate. However, leachate loading rates to the anammox reactor are critical\ud due to the high concentrations of potential anammox inhibitors, including\ud heterogenous organic carbon, heavy metals, pesticides and nitrite.\ud In this study, anammox bacteria were enriched from two sources; sludge from\ud the world’s first full-scale anammox plant (Dokhaven wastewater treatment plant) in\ud Rotterdam, Netherlands and sludge from the Virginia Hampton Roads Sanitation\ud District (HRSD) wastewater treatment facility, the first full-scale anammox plant in the\ud United States. The sludge was enriched over 14 months in two sequencing batch\ud reactors (SBR) and about a year period in a novel carbon nanotube membrane upflow\ud anaerobic sludge blanket (MUASB) reactor. Of the two systems, SBR and MUASB, the\ud MUASB was much more effective at enriching anammox bacteria due to its ability to\ud capture planktonic anammox cells and enhance the anammox granulation process.\ud First-order, Grau second-order, Stover-Kincannon kinetic models were developed for\ud both SBRs, with the second order Grau and Stover-Kincannon kinetic models\ud describing the SBRs most accurately.\ud To determine the effect of landfill leachate loading rates on anammox activity,\ud partially nitrified Coffin Butte landfill leachate (Benton County, OR) was fed to MUASB\ud reactor over a variety of nitrogen loading and hydraulic retention times. A Stover-Kincannon model was developed for the MUASB reactor with and without leachate\ud present in the anammox media. It was observed that the Stover-Kincannon model\ud constants were affected and decreased in presence of leachate in the media. The\ud maximum substrate utilization rate (U[subscript max])decreased by the factor of 11 and saturation\ud constant (K[subscript B]) decreased by the factor of 29. Therefore, the inhibition observed here\ud is most likely best described by mixed inhibition kinetics, and organic carbon present\ud in the leachate was suspected to be a major cause of the observed anammox\ud inhibition. The leachate was pretreated with a FeCl₃. 6H₂O coagulation process to help\ud alleviate the observed anammox inhibition. This process removed 40% of the organic\ud carbon from the leachate. However, the pretreated leachate still induced a 40%\ud inhibition of the anammox processes. This suggests that the FeCl₃. 6H₂O pretreatment\ud process did not remove enough of the organic carbon to prevent inhibition from\ud occurring