Microbial community stratification in Membrane-Aerated Biofilm Reactors for Completely Autotrophic Nitrogen Removal

Carles Pellicer i Nàcher, Maël Ruscalleda, Akihiko Terada, Barth F. Smets

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Abstract

Due to the necessity of a source of nitrite, most of the processes involving Anaerobic Ammonium Oxidation (Anammox) are based on a separated two-step process with a previous partial-nitritation reactor. However, these two processes can occur simultaneously in the same reactor by taking advantage of bacterial granules or biofilms. In this sense, completely autotrophic nitrogen removal from high ammonium strength wastewater was achieved in a Membrane-Aereated Biofilm Reactor (MABR) in a single step. Here, a biofilm containing nitrifiers (Aerobic Ammonium and Nitrite Oxidizing Bacteria, AOB and NOB, respectively) and Anaerobic Ammonium Oxidizing Bacteria (AnAOB) is grown on bubbleless aeration membranes to remove ammonium. Since oxygen permeates through the membrane-biofilm interface while ammonium diffuses into the biofilm from the biofilm-liquid interface, oxygen gradients can be established across the biofilm, allowing nitrogen removal in a single reactor by simultaneous activity of the mentioned biocatalysts. This work consists on the analysis of the microbial community existing in two laboratory-scale reactors operated for more than 300 days, which removed up to 5.5 g-N/m2/day. The system contained 1028 hollow fiber membranes (200/280 µm inner/outer diameter) covered homogeneously by biofilm. Samples (low, middle and upper part of the biofilm) were collected, fixed, embedded in OCT compound for cryosection and later Fluorescence In-Situ Hybridization (FISH). Emphasis was put on elucidating the radial and longitudinal distribution and quantification of the involved microbial communities along the membranes. Our observations confirmed that the oxygen gradient was conditioning the spatial distribution of each population inside the biofilm. Thus, AOB were mainly located in the adjacent zone to the membrane, while AnAOB were localized next to them in areas where no oxygen was available. NOB were detected in very low amounts. Results proved the feasibility of developing biofilm structures for high-rate completely autotrophic nitrogen removal.
Original languageEnglish
Publication date2010
Publication statusPublished - 2010
EventWater Research Conference 2010 - Lisbon, Portugal
Duration: 11 Apr 201014 Apr 2010

Conference

ConferenceWater Research Conference 2010
CountryPortugal
CityLisbon
Period11/04/201014/04/2010

Keywords

  • Nitrogen removal
  • Membrane-Aerated Biofilm Reactor
  • Anammox
  • biofilms stratification
  • Anaerobic Ammonium Oxidization

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