| Many processes generate high-salinity wastewaters, which contain at least 1% total dissolved solids. Salt concentrations more than 1% can cause bacterial plasmolysis and loss of the metabolic functions. For this reason, high-salinity wastewater is often difficult to treat using biological processes. When the microorganisms are acclimated in high salt concentrations for a long period, the cultures are capable of surviving in hypersaline environments by regulating their metabolic functions. Carbon removal in high-salinity wastewater has been widely studied. However, biological nitrogen and phosphorus removal in high salinity wastewater seems to be very poorly studied. And the effect of salt content on conventional cultures is not clear. In this research, the activated sludge derived from conventional treatment processes was acclimated in the saline environment by gradually increasing salinity. And the effects of high salinity on the nitrifiers, denitrifiers and phosphate accumulating microorganisms (PAO) during the acclimation period were investigated.In preliminary research, the effects of salt contents on the municipal activated sludge (non-adapted activated sludge) were studied. The results showed that the bioactivities of non-adapted sludge decreased remarkably when the system was shocked with high salt concentrations. During the shock stage, the specific oxygen uptake rate SOUR decreased 70% at salt content of 30 g/L. Nitrobacter seemed to be more sensitive to high salinity than Nitrosomonas. The nitrification process was completely inhibited at salt content of 10 g/L. The denitrifiers possessed a better salt tolerance capability than the nitrifiers. When PAO was subjected to shock loads of salt, phosphate release under anaerobic conditions and phosphate uptake under aerobic conditions were inhibited severely. Complete loss of phosphate accumulation capability appeared at salt content of 20 g/L.It was observed that the amount and species of protozoa reduced gradually with...
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