Application of the anammox process under microaerophile conditions to anaerobic digestates for nitrogen removal and bio-induced phosphorus precipitation

Direct wastewater discharges to the environment will cause problems due to the uncontrolled availability of nutrients. Energy consumption in wastewater treatment must be optimized to promote sustainability. Moreover, nutrients can be recovered as a resource to produce agricultural fertilizers in the framework of the circular economy. Partial nitrification combined to anaerobic ammonium oxidation -anammox- (PNA) allows for fully autotrophic nitrogen removal from wastewater, which implies significant energy savings with respect to conventional treatment alternatives Additionally, phosphorus bio induced mineralization may be an interesting way for the recovery of this nutrient. This work deals with the start-up of a PNA process in one SBR using granular biomass for the treatment of the anaerobically digested sludge dewatering centrate produced in the side stream of a municipal wastewater treatment plant. This study has been carried out in the framework of the R & D project “DIGESTAKE” (COMRDI-16-0061). The start-up of the PNA SBR was successfully achieved after 200 days. Final ammonium removal rate reached was about 300 mg N L-1 d-1. The emission of N2O was identified as potentially significant. The growth of granular biomass was characterized. Final suspended solids content in the reactor was 2739 mg L-1 (95% volatile). However, phosphate bio induced mineralization was not significantly achieved. The addition of an extra amount of calcium or magnesium ions inside the reactor is advised to promote such process ​
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