Pilot-scale evaluation of anammox-based mainstream nitrogen removal from municipal wastewater

Abstract

Autotrophic nitrogen removal in the mainstream wastewater treatment process is suggested to be a prerequisite of energy autarkic wastewater treatment plants (WWTP). Whilst the application of anammox-related technologies in the side-stream is at present state of the art, the feasibility of this energy-efficient process at mainstream conditions is still under development. Lower operating temperature and ammonium concentration, together with required high nitrogen removal efficiency, represent the main challenges to face in order to reach this appealing new frontier of the wastewater treatment field. In this study, we report the evaluation of the process in a plug-flow granular sludge-based pilot-scale reactor (4 m³) continuously fed with the actual effluent of the A-stage of the WWTP of Dokhaven, Rotterdam. The one-stage partial nitritation–anammox system was operated for more than 10 months at 19 ± 1°C. Observed average N-removal and ammonium conversion rates were comparable or higher than those of conventional N-removal systems, with 182 ± 46 and 315 ± 33 mg-N L⁻¹ d⁻¹, respectively. Biochemical oxygen demand was also oxidized in the system with an average removal efficiency of 90%. Heterotrophic biomass grew preferentially in flocs and was efficiently washed out of the system. Throughout the experimentation, the main bottleneck was the nitritation process that resulted in nitrite-limiting conditions for the anammox conversion. Anammox bacteria were able to grow under mainstream WWTP conditions and new granules were formed and efficiently retained in the system.

Keywords:

• anammox
• municipal wastewater
• low temperature
• mainstream
• autotrophic nitrogen removal

Acknowledgements

The authors gratefully thank Stefan Geilvoet, René Pasch and Maaike Hoekstra for their valuable work in the laboratory and for discussions, and Udo van Dongen and Marianna Perra for the help with FISH analysis. Jordi Gabarró i Bartual is acknowledged for his valuable help with graphics. The authors thank the operators and technologists of the water boards of Waterschap Hollandse Delta (WSHD) for their kind collaboration.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Funding

This research was funded in the framework of the CENIRELTA [LIFE11 ENV/NL/785]. Z.H. was supported by ERC [232937] and B.K. was also supported by the Netherlands Organization for Scientific Research [VENI grant 863.11.003].

Supplemental data

Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/09593330.2014.982722.