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Since the industrial revolution, the combustion of fossil fuels growing cause of greenhouse gases in the atmosphere, especially the C02 concentration is getting higher and higher, giving rise to elevated temperatures, rising sea levels, flooding and extinction of flora and fauna. Take cost-effective method to control greenhouse gas emissions, has become the hotspot of global environmental protection. Although people in the reduction and inhibition of C02 emissions technology more research, these technologies, however, the prevalence of high operating costs and operational complexity, constraints to promote the use of large-scale sequestration technologies. Municipal sewage treatment plant sludge is rich in N, P, K and other nutrients and trace elements. Using sludge cultivation of marine microalgae, not only can save a lot of microalgae culture medium, and the production of microalgae can also be used as chemical raw materials, utilization of sludge. For these reasons, the present study screened out from 12 species of marine microalgae, an acid-resistant and resistant to high concentrations of C02 marine microalgae for the fixation of the C02, while using sewage sludge microalgae extract as nitrogen, phosphorus nutrients in order to reduce the cost of carbon sequestration, optimize microalgae growth conditions on the basis of microalgae were inoculated into the spiral light bioreactor, and determination of the carbon sequestration capacity. The main results are as follows: (1) optimize the extraction conditions on the basis of comparison of the effect of hot soda, of ultrasonic processing bases ultrasonic extraction method of sludge nutrients and reduction effect. The results show that the hot alkali suitable extraction conditions for the pH = 13, T = 100 ° C, t = 9h; the ultrasonic method suitable extraction conditions t = 40min; and plus alkali ultrasonic method in pH = 13, pH = 400W, t = 20min when extracted the best results. Optimized extraction conditions, the extraction of the three methods of the sludge N, P in descending order: alkali ultrasonic method to ultrasonic gt; extraction rate of hot alkali, in which the ultrasonic method of N, P 33.48%, 57.5%, respectively. Considering the sludge N, P extraction and subsequent microalgae culture pH value, to determine the optimum method of ultrasonic sludge nutrient extraction. (2) microalgae algal cell density changes in the different initial pH values ??of F / 2 medium was measured using a microplate absorbance method to compare the various microalgae H2SO4 and HNO3 due to the acidic adaptability; acid resistance strong microalgae were inoculated into the medium, the continuous flow rate of 75ml/min pass into the volume fraction of 15% of C02, and the growth of microalgae to pass into the air medium as a control, according to the algal cells during culture 7d density and biomass trends, further screening is resistant to high concentrations of C02 algae species. The results showed that 12 kinds of tested microalgae Dunaliella salina (Dunaliella tertiolecta), Spirulina platensis (Spirulina platensis), marine Chlorella (Chlorella pacifica) closterium (Nitzschia Closterium), Asian Heart shaped flat algae (Platymonas subcordiformis), Chaetoceros gracilis (Chaetoceros gracilis) viridis (Pavlovaviridis Tseng) acid resistance is strong, normal growth in the initial pH = 4 medium; Chaetoceros gracilis and unique algae species capable of withstanding 15% CO2 impact, after the end of the culture, 15% CO2 Processing group algal biomass reaches 102.47% of the control group. Therefore, Chaetoceros gracilis has good application potential in terms of fixed high concentrations of CO2 and mitigate the greenhouse effect. (3) a mixture of sludge extract and sea, the optimal conditions for the growth of Chaetoceros gracilis: 10% CO2 gas source into the sludge extract and seawater mixed in accordance with the proportion of 1:29, a temperature of 30 ° C , light intensity 60001x. (4) homemade 10L spiral pipe photobioreactor inoculated Chaetoceros gracilis, meet the optimization of the growth conditions on the basis of further bioreactor operating conditions: inoculum size 1 × 106cell/ml the circulating flow rate of 1200 ml / h pass into the 10% CO2 flow rate 20ml/min. The dynamic cycle operation during the 7 days, the growth of microalgae good run 5d highest carbon sequestration rate, reaching 0.67 gCO2 of / L · d. , Chaetoceros gracilis able to quickly absorb mixed inorganic nutrients in the culture medium, running after 7 days, NO3 - N, NH4-N, NO2 - N, PO43 - P the removal rates reached 96.92%, 93.32% , 77.48% and 88.52%, mixture of N, P concentration can reach the \In short, the of Chaetoceros gracilis both strong acid resistance, while in 15% of the CO2 concentration in the normal growth, suitable for industrial emissions of CO2 fixed. The surplus sludge of sewage as Chaetoceros gracilis culture media, both to reduce the cost of microalgae production, but also help the sludge reduction and resource. Therefore, the combination of the the sludge utilization of microalgae solid carbon technology to reduce industrial CO2 emissions and slow down the greenhouse effect has broad application prospects.
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