[Effect of Influent Ammonia Concentration on a Biological Phosphorus Removal Granules System]

Mature biological phosphorus removal granules were inoculated into a SBR. The effect of the ammonia concentration on biological phosphorus removal granules system was investigated by increasing the concentration of ammonia in the influent. The ability of the system to withstand ammonia loading was determined. The results showed that when the influent ammonia concentration was below 45 mg·L^-1, the biological phosphorus removal granule system showed good performance. The TP removal efficiency was above 96%, the COD removal efficiency was over 89%. The effluent TP concentration and COD concentration were 0.4 mg·L^-1 and 25 mg·L^-1 respectively. The particle size was above 950 μm and the SVI was below 45 mL·g^-1. When the influent ammonia concentration was 60 mg·L^-1, the removal efficiency of TP was more than 95%. The effluent TP concentration was below 0.5 mg·L^-1, the particle size was 760 μm, and the SVI was 56 mL·g^-1. Furthermore, the biological phosphorus removal granules partially disintegrated and the metabolism and growth of PAOs began to be inhibited in the system. When the influent ammonia concentration reached 70 mg·L^-1, the removal efficiency of TP was 70%, the effluent TP concentration was about 3 mg·L^-1, the particle size was 570 μm, the SVI was 75 mL·g^-1, and the value of PN/PS was about 7.50. The biological phosphorus granules severely disintegrated and the metabolism and growth of PAOs was severely inhibited in the system. Moreover, as the influent ammonia concentration increased, the protein increased and polysaccharide decreased from the microbial secretion of biological phosphorus removal granules. Moreover, the value of PN/PS increased, the biological phosphorus removal granules disintegrated, the particle size decreased, the SVI increased, and the structure and function of the biological phosphorus removal granules were destroyed.