| Phosphorus is an essential element of living organisms as well as a nutrient for biological growth. Compared to chemical treatment method, enhanced biological phosphorus removal (EBPR) system is more economical and has less impact on environment during the long term operation. In EBPR system, it is generally believed that phosphorus accumulating organisms (PAOs) play a major role in phosphorus removal. PAOs could release phosphorus under anaerobic condition and absorb phosphorus under subsequent aerobic condition. Phosphorus is accumulated in cells. What’s more, because of the adsorption and biological flocculation, EPS is applied to sewage flocculation and precipitation, heavy-metal removal and so on. Studies have found that EPS play a roal in phosphorus removal.Microorganism growth is inhibited in high-salinity environment. Microorganism could not play an active role in dealing with high-salinity wastewater. Hence the traditional biological treatment method was greatly restricted. What’s more, salt-tolerant sludge acclimation period is very long and the process of start-up is difficult. Therefore, utilizing halophilic bacteria which grows in saline environment directly is more efficient and rapid.An aerobic marine effective phosphorus removing strain was screened out from the sediment of the South China Sea. The strain was identified as Shewanella and named after Shewanella sp. CF8-6. The phosphorus absorption ability and mechanism of the strain was studied through batch experiments.The phosphorus removal rate was more than 90% and residual phosphorus concentration in the environment was less than 0.3 mg/L when phosphorus concentration was lower than 12.4 mg/L. Phosphorus absorbed by bacteria was not released to environment obviously even at the decline phase. The strain had a strong capability of phosphorus fixation.Effects of temperature, pH, C/N, dissolved oxygen (DO) and salinity on bacteria growth and phosphorus removal efficiency were analyzed. The adaptive range of strain to environment was confirmed. The concentration of phosphorus was reached to standard under the action of Shewanella sp. CF8-6 at 5-35℃. It showed that this strain was able to resist temperature change of the seasons. Especially, there is a broad application prospect of phosphorus removal process in low temperature conditions. Shewanella sp. CF8-6 has certain adjustment ability to pH. Changes of microorganism growth and phosphorus removal efficiency were little under the condition of pH 5.8-9.58. The largest biomass at the stationary phase was nearly the same and the phosphorus removal efficiency was reached over 95%. The phosphorus removal efficiency of Shewanella sp. CF8-6 was not inhibited because of excessive C/N. The higher C/N ratio, which means the more sufficient carbon source, led to the larger maximum biomass and the longer stationary phase. The phosphorus removal efficiency was reached over 95% so long as C/N>7. When DO was above 5.2 mg/L, the bacterial growth rate increased gradually but the maximum biomass at the stationary phase was not changed with the increase of DO concentration. The phosphorus removal efficiency was above 90%. It illustrated that the strain is aerobic bacteria. Shewanella sp. CF8-6 has a strong adaptability to salinity. The strain could grow in the salinity of 0-15% and had a favorable phosphorus removal capability when the salinity was 0-12%. It indicated that the strain could be applied in treating high-salinity wastewater containing phosphorus.In EBPR system, it is considered that the excessive phosphorus absorption ability of PAOs play a major role in phosphorus removal. However, Shewanella sp. CF8-6 didn’t produce polyphosphates accumulated inside cells. The strain combined phosphorus with glycoprotein in EPS. Phosphomonoester was accounted for 92.6%, of which the major form was D-glucose-6-phosphate. All of the phosphorus into cells was formed phosphomonoester.The efficient phosphorus removal bacteria Shewanella sp. CF8-6 screened in this study had quite strong environment adaptiveness and a broad application prospect. The phosphorus adsorpted by bacteria combined with extracellular glycoproteins to form phosphomonoester. A new view for the research of sewage biological phosphorus removal mechanism is provided. |
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