The Effect Of The Acclimation Strategy On The Biological Nitrification And Denitrification In The Salinity Wastewater

In coastal areas, seawater infiltration into the sewers could cause the sudden increase of the salinity in the sewage. The biological treatment is usually used in the municipal wastewater treatment plant. Now the conclusions about the effect of salinity shock on the microorganisms in the biological system are inconsistent. In the biological treatment of salinity wastewater, the microorganisms need to be acclimated in the saline sewage. And the acclimation strategy is an important factor affecting the effluent treatment performance. However, there are few studies about the effect of acclimation strategy on the nitrification and denitrification in the saline wastewater treatment. In this research, batch experiments were conducted to study the effects of salinity shock on the microorganism in the conventional activated sludge. And different acclimation methods were used in two sequencing batch reactors (SBRs). During the period of acclimation, the process of nitrification and denitrification were investigated.The results showed that the bioactivities of the activated sludge decreased 79% at salt content of 20 g/L. Nitrosomonas was inhibited79% at salt content of 15 g/L. Nitrobacter seemed to be more sensitive to the salinity shock than Nitrosomonas. Nitrosomonas and Nitrobacter were completely inhibited when the salt content was over 25 g/L. Compared with the Nitrosomonas and Nitrobacter, the denitrifiers possessed a better salt tolerance capability. The degree of inhibition was 25% at the salt content of 20g/L.The phosphate accumulating organisms (PAO) were also sensitive to the salinity shock. At the salt content of 10g/L, the anaerobic phosphate release and the aerobic phosphate uptake were inhibited 36% and 94%, respectively.In this research, different acclimation methods were used in two reactors. The increments of the NaCl concentration were 5g/L and 2.5 g/L in reactor 1 and reactor 2, respectively. In reactor 1, Nitrosomonas could be adapted to the salt content of 25 g/L after 50 days of acclimation. The specific ammonia oxidation rates in reactor 1 were 2.07³.08mgNH₄⁺-N/gMLSS·h. When the salt concentration was lower than 15 g/L, the ammonia oxidation rates in reactor 2 were slightly higher than those in reactor 1. Nitrobacter was inhibited severely at the salt content of more than 15 g/L, which resulted in the short nitrification in two reactors. After a period of acclimation, the denitrifiers could be adapted to the high salinity. The specific denitrification rates in reactor 2 were also slightly higher than those in reactor 1. During the process of acclimation, it was found that there were large amount of filamentous bacterium in two reactors. And the amount of filamentous bacterium in reactor 1 was higher than that in reactor 2. The sludge volumetric indexes were high, which meant that bad settling properties appeared in the two reactors.