Nitritating-anammox biomass tolerant to high dissolved oxygen concentration and C/N ratio in treatment of yeast factory wastewater

Abstract

Maintaining stability of low concentration (<1 g L⁻¹) floccular biomass in the nitritation-anaerobic ammonium oxidation (anammox) process in the sequencing batch reactor (SBR) system for the treatment of high COD (>15,000 mg O₂ L⁻¹) to N (1680 mg N L⁻¹) ratio real wastewater streams coming from the food industry is challenging. The anammox process was suitable for the treatment of yeast factory wastewater containing relatively high and abruptly increased organic C/N ratio and dissolved oxygen (DO) concentrations. Maximum specific total inorganic nitrogen (TIN) loading and removal rates applied were 600 and 280 mg N g⁻¹ VSS d⁻¹, respectively. Average TIN removal efficiency over the operation period of 270 days was 70%. Prior to simultaneous reduction of high organics (total organic carbon>600 mg L⁻¹) and N concentrations>400 mg L⁻¹, hydraulic retention time of 15 h and DO concentrations of 3.18 (±1.73) mg O₂ L⁻¹ were applied. Surprisingly, higher DO concentrations did not inhibit the anammox process efficiency demonstrating a wider application of cultivated anammox biomass. The SBR was fed rapidly over 5% of the cycle time at 50% volumetric exchange ratio. It maintained high free ammonia concentration, suppressing growth of nitrite-oxidizing bacteria. Partial least squares and response surface modelling revealed two periods of SBR operation and the SBR performances change at different periods with different total nitrogen (TN) loadings. Anammox activity tests showed yeast factory-specific organic N compound-betaine and inorganic N simultaneous biodegradation. Among other microorganisms determined by pyrosequencing, anammox microorganism (uncultured Planctomycetales bacterium clone P4) was determined by polymerase chain reaction also after applying high TN loading rates.

Keywords:

• anammox
• SBR
• yeast factory wastewater
• denitrification
• total nitrogen removal rate

Acknowledgements

Ms Anne Paaver is acknowledged for the analyses of water samples. Anne Menert, Madis Metsis and Jaak Simm are thanked for microbial analysis. Hannover University is acknowledged for inoculum