Development of denitrifying phosphate accumulating and anammox micro-organisms in anaerobic hybrid reactor for removal of nutrients from low strength domestic sewage

Low strength domestic sewage was treated in an Anaerobic Hybrid Reactor. The first phase was focused on the enhancement of denitrifying phosphate accumulating organisms (DPAOs) for the concurrent removal of nitrogen and phosphate. 16S rRNA gene confirmed the presence of Flavobacterium spp. and Pseudomonasalcaligenes spp. which are dominant DPAOs. The second phase was the anaerobic ammonium oxidation (anammox) enrichment phase, and it exhibited much higher chemical oxygen demand (87%) and nitrogen removal (90%) as compared to the first phase. However, it had failed to remove the phosphate from the system. In case of anammox, the dominant specie detected was Candidatus Brocadia, along with minor counts of Candidatus Jettenia and Anammoxoglobus Propionicus. Apart from that, ammonia oxidizing bacteria (Nitrosomonas europaea, Nitrosomonas nitrosa) and methanogens (Methanosaeta, Methanobacterium) were also detected in the system. This study showed the feasibility of anammox species over DPAOs in treating domestic sewage.