Article pubs.acs.org/est
Anammox Growth on Pretreated Municipal Wastewater Tommaso Lotti,† Robbert Kleerebezem,† Charlotte van Erp Taalman Kip,‡ Tim L. G. Hendrickx,§ Jans Kruit,§,∥ Maaike Hoekstra,† and Mark C. M. van Loosdrecht*,† †
Department of Biotechnology, Delft University of Technology, Julianalaan 67, Delft 2628 BC, The Netherlands Waterschap Hollandse Delta, Handelsweg 100, Ridderkerk 2988 DC, The Netherlands § Paques BV, T. de Boerstraat 24, Balk 8561 EL, The Netherlands
Environ. Sci. Technol. 2014.48:7874-7880. Downloaded from pubs.acs.org by UNIV OF FLORIDA on 01/07/19. For personal use only.
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ABSTRACT: Autotrophic nitrogen removal from municipal wastewater enables development of energy autarkic wastewater treatment plants. In this study we report the evaluation of the anammox process in a granular sludge fluidized bed lab-scale reactor continuously fed with the actual effluent of the A-stage of the WWTP of Dokhaven, Rotterdam. The reactor was anoxic, and nitrite was dosed continuously to support anammox activity only. The system was operated for more than ten months at temperatures between 20 and 10 °C. COD was also consumed during the process, but heterotrophs could not outcompete anammox bacteria. Volumetric N-removal rates obtained were comparable or higher than those of conventional N-removal systems, with values higher than 0.4 g-N L−1 d−1 when operated at 10 °C. The biomass specific N-removal rate at 10 °C was on average 50 ± 7 mg-N g-VSS−1 d−1 during the last month of operations, almost two times higher than previously reported activities at this temperature. FISH analysis revealed that the dominant anammox species was Candidatus Brocadia Fulgida throughout the experimentation. Evidence for growth of anammox bacteria at mainstream conditions was demonstrated for the entire temperature range tested (10−20 °C), and new granules were shown to be actively formed and efficiently retained in the system.
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INTRODUCTION To date, most of the autotrophic nitrogen removal systems reported in the literature were operated at temperatures exceeding 25 °C and influent nitrogen concentrations over 0.1 g-N L−1.1,2 The application at lower temperatures and lower nitrogen concentrations would allow for extending the application potential of processes involving anammox to municipal sewage treatment opening new possible scenarios in designing energy producing wastewater treatment plants.3−5 In order to maximize energy recovery from municipal wastewater energetic valorisation of organic carbon in a first step would be most advantageous. This first step could either be a UASB reactor at tropical climates6 or a CODconcentration step at lower temperature regions. This concentration can be performed by physical (e.g., sieving), chemical (e.g., precipitation), or biological7 methods or combinations thereof. The concentrated sludge can subsequently be digested anaerobically to methane containing biogas. The remaining liquid contains ammonium that can be removed in an autotrophic process based on anammox.2,3,8−10 To facilitate autotrophic nitrogen removal on pretreated sewage a process based on prevention of growth of nitrite oxidizing bacteria (NOB) and retaining anaerobic ammonium oxidation (anammox) bacteria in the system in symbiosis with ammonium oxidizing bacteria (AOB) has to be developed. The main challenge for applying anammox in the water line of WWTP is to achieve a high rate process with good biomass retention and low effluent nitrogen concentrations at low water © 2014 American Chemical Society
temperatures. A very strong decrease in specific anammox activity was reported after lowering the temperature of warm reactors.11−13 Despite this decrease in anammox activity, several laboratory studies have reported 1-stage partial nitritation/ anammox at lower temperatures (≤25 °C) and reasonable conversion rates higher than 0.2 g-N L−1 d−1 at 15 °C.13−16 Hendrickx et al.17 and Isaka et al.12 studied the anammox process at low temperature in anoxic reactors (2nd step of the 2-stages partial nitritation/anammox process) fed with synthetic feeding-medium, and volumetric N-removal rates of 0.26 and 0.36 g-N L−1 d−1 were reported at 10 and 6.3 °C, respectively. Until now no report is available describing the application of anammox based process treating actual municipal wastewater. In natural ecosystems such as Northern European soils and marine sediments, anammox bacteria thrive at low temperatures (
