Start‐up and enrichment of a granular anammox SBR to treat high nitrogen load wastewaters

BACKGROUND: Landfill leachate is characterized by low biodegradable organic matter that presents difficulties for the complete biological nitrogen removal usually performed by conventional biological nitrification/denitrification processes. To achieve this, the anaerobic ammonium oxidation (anammox) process is a promising biological treatment. This paper presents an anammox start‐up and enrichment methodology for treating high nitrogen load wastewaters using sequencing batch reactor (SBR) technology. RESULTS: The methodology is based on the gradual increase of the nitrite‐to‐ammonium molar ratio in the influent (from 0.76 to 1.32 mole NO₂^?‐N mole^?1NH₄⁺‐N) and on the exponential increase of the nitrogen loading rate (NLR, from 0.01 to 1.60 kg N m^?3 d^?1). 60 days after start‐up, anammox organisms were identified by polymerase chain reaction (PCR) technique as Candidatus Brocadia anammoxidans. After one year of operation, NLR had reached a value of 1.60 kg N m^?3 d^?1 with a nitrogen (ammonium plus nitrite) removal efficiency of 99.7%. The anammox biomass activity was verified by nitrogen mass balances with 1.32 ± 0.05 mole of nitrite removed per mole of ammonium removed and 0.23 ± 0.05 mole of nitrate produced per mole of ammonium removed. Also, enrichment of anammox bacteria was quantified by fluorescence in situ hybridization (FISH) analysis as 85.0 ± 1.8%. CONCLUSIONS: This paper provides a methodology for the enrichment of the anammox biomass in a SBR to treat high nitrogen loaded wastewaters. Copyright © 2007 Society of Chemical Industry     

Operational strategy for a partial nitritation–sequencing batch reactor treating urban landfill leachate to achieve a stable influent for an anammox reactor

BACKGROUND: In recent years, new technologies have been developed to deal with streams with high nitrogen loads, most of them based on the anammox process. As a first step in this process, ammonium has to be partially oxidized to nitrite. This partial nitritation is usually carried out through the SHARON process. However, it can also be achieved using other configurations (sequencing batch reactor or biofilm airlift, among others). The aim of this paper is to compare two different feeding strategies (fed‐batch and step‐feed) for the operation of a partial nitritation–sequencing batch reactor (PN‐SBR) treating raw urban landfill leachate. RESULTS: A PN‐SBR treating urban landfill leachate was started up and operated using two different feeding strategies: fed‐batch and step‐feed. When the experimental results were compared, it could be seen that during the step‐feed strategy the system was more stable and presented a better performance. In addition, a cycle profile evolution of the reactor in each strategy was carried out to study the dynamics of the main chemical compounds, as well as different physical parameters. The profiles were similar for the nitrogen compounds, but with a difference in behaviour of pH, inorganic carbon and oxygen uptake ratio, which could explain the better performance and stability of the step‐feed strategy. CONCLUSIONS: This study has demonstrated that the step‐feed strategy is more suitable than the fed‐batch because it performs better overall, there is less fluctuation in its operation and it has higher effluent quality stabilization. Copyright © 2008 Society of Chemical Industry