Oxygen-limited nitrogen removal in a lab-scale rotating biological contactor treating an ammonium-rich wastewater

Abstract

A lab-scale Rotating Biological Contactor (RBC) was operated with the purpose of oxygen-limited (autotrophic) nitrification-denitrification of an ammonium-rich synthetic wastewater without Chemical Oxygen Demand (COD). Based on the field observations that RBCs receiving anaerobic effluents come to anoxic ammonium removal, the RBC was inoculated with methanogenic sludge. Some 100 days after the addition of the anaerobic sludge to the reactor as a possible means of a rapid initiation of the nitrogen (N) removal process, a maximum ammonium removal of 1,550 mg N m(-2) d(-1) was achieved. Batch tests with 15N labeled ammonium and nitrite indicated that a large part of that N was removed via oxygen-limited oxidation of ammonium with nitrite as the electron acceptor. The other part was removed via conventional denitrification, presumably with COD released from lysis of cells. Species identification of the most abundant microorganisms revealed that Nitrosomonas spp. were the dominant ammonium-oxidizers in the sludge. Thus far, the molecular characterization of the sludge could not show the presence of Planctomycetes among the most dominant species. Overall this experiment confirms the property of the RBC system to remove ammonium to nitrogen gas without the use of heterotrophic carbon source.

Characterization of an Autotrophic Nitrogen-Removing Biofilm from a Highly Loaded Lab-Scale Rotating Biological Contactor

“…Due to the dynamic behavior (sloughing and regrowth of the outer layers) of a biofilm and the lack of available O 2 at higher N loads, NOB were probably unable to maintain themselves in large numbers in the biofilm and most probably washed out. A biofilm sample supplied with NH 4 ϩ and NO 2 Ϫ under aerated conditions did not show any N removal, indicating that the N removal process in the RBC occurred via anoxic ammonium oxidation, which was also deduced from earlier 15 N-labeling experiments (37). Indeed, 76.5 Ϯ 6.4 mg of N g of VSS Ϫ1 day Ϫ1 was removed, a similar value to that reported for the Anammox process, with the higher NO 2 Ϫ and N 2 levels per unit NH 4 ϩ possibly caused by some activity of nitrifiers and heterotrophic denitrifiers (equation 6).…”

“…2A). However, despite the initial presence of NOB based on high NO 3 Ϫ production during periods before the one described in this paper (36,37), the long-term (more than 600 days of operation) oxygen-limited conditions in the RBC reactor established a biofilm in which the NOB were apparently outcompeted (Fig. 2B).…”

“…17 h). Detailed information on the reactor performance prior to the period described in this paper is published elsewhere (36,37).…”

“…In a second phase, granular anaerobic sludge from a full-scale upflow anaerobic sludge blanket reactor treating potato-processing wastewater (Primeur, Waregem, Belgium) was added to this reactor as a second biocatalyst inoculum. High N removals were achieved afterward, which were shown to be due to a coupling of NH 4 ϩ and NO 2 Ϫ to N 2 under anoxic conditions (37). In this paper, we describe several important physiological and microbial characteristics of the RBC biomass that developed from these two different kinds of biocatalyst after long-term operation on a synthetic NH 4 ϩ wastewater devoid of organic carbon.…”

Anaerobic ammonium oxidation for treatment of ammonium-rich wastewaters

“…Unlike the co-existence of AOB and the ANAMMOX bacteria, nitrifying bacteria such as Nitrosomonas eutropha conduct aerobic ammonium oxidation and anaerobic ammonium oxidation simultaneously. Impressively, molecular biological experiments discovered that typical ANAMMOX species Kuenenia stuttgartiensis was active in the OLAND system as well (Pynaert et al, 2002).…”