Optimization Of Photosynthetic Bacteria Culture Process And Application In Wastewater Treatment

Photosynthetic bacteria is a general term for prokaryotes with photosynthesis systems,which plays an important role in food additives processing,clean energy production,poultry farming,crop planting,and environmental management.At present,low biomass and high cost in photosynthetic bacteria cultivation restrict the application of photosynthetic bacteria.To solve these problems,the photosynthetic bacteria separated from pond mud of Chongming were optimized for culture conditions,culture medium and feeding strategies.Rhodospirillum rubrum were studied on the continuous flow sewage treatment.The optimal growth temperature and light intensity of R.rubrum cultivation were 25 ℃ and 5000 LUX.While the optimal growth temperature of mixed microbes cultivation were 28 ℃,not sensitive to light intensity between 2000-6000 LUX.The Plackett-Burman experiment,the steepest climbing experiment and Box-Behnken experiment were carried to optimize the culture medium of R.rubrum and mixed bacteria respectively.Finally,the highest biomass concentration of R.rubrum and mixed microbes reached 0.425 and 0.618 g/L,which was 40.77%and 34.15%higher than that of control,respectively.The fed-batch fermentation was implemented for further improving the biomass growth rate and concentration.The effects of different carbon source feeding strategies in R.rubrum cultivation was investigated.Results showed that maintain the sodium succinate concentration and sodium acetate at 0.2 and 0.16 g/L from 48 h greatly stimulated the cell growth rate.The biomass of R.rubrum could improved to 0.76 g/L,79%hiher than the control.The study found that the reincreasing of ORP value during later stage of growth implied insufficiency of sodium succinate in mixed microbes cultivation.A creative process controlling straregy through the feedback control of sodium succinate by ORP value was implemented,under which the highest biomass reached 1.46 g/L,115%higher than that of control.The R.rubrum was applied to the simulated piggery wastewater treatment.The results showed that the optimal treatment condition was micro-aerobic-light and the optimal concentration of organic compound was 3000 mg/L.Under continuous flow treatment,the optimal hydraulic retention time was 72 h and the COD removal rate was 0.715 g/L/d.