Factors Influencing Oxygen Supply Efficience Of Algae On System Of Algae Culture From Municipal Wastewater

Based on that the sewage treatment via micro algae cultivation and couplingtechnology of biological diesel production aim to purify sewage and get high fatmicro algae which can produces biodiesel, the key is to make algae providemaximum oxygen, which makes the organic solution in the sewage decompose intocarbon dioxide and carbonate with the aerobic bacterial action. Thus, carbon isprovided continuously. The purpose of this paper is to determine best condition ofoxygen that is adopted to cultivate microalgae in urban sewage.With the consultation of literature and research group, the approach ofphotosynthetic oxygen evolution rate admeasurement is adopted to determine thebest conditions that the276scenedesmus obliquus and9chlorella pyrenoidosaproduce oxygen effectively in various growth stages. Concurrently, the promotionand primary mechanism of the magnetic field is also explored. The besttechnological condition of solubility of oxygen in water is determined via themeasurement of oxygen transfer coefficient. Additionally, Outdoor experiment isadopted to improve the illuminant.The research results are shown as follows：（1） The experiment found that dissolved oxygen under saturation conditionthrough the algae culture process.The maximum dissolved oxygen concentration of276scenedesmus obliquus is29.96mg/L and the maximum dissolved oxygenconcentration of9chlorella pyrenoidosa is27.53mg/L. And dissolved oxygenconcentration and pH value changes have significant correlation.（2） Considerations from the efficiency of oxygen production: The two kindsof algae are suitable for medium illumination intensity.saturation light intensity isabout500μmol·m^-2·s^-1. After saturation point all appear different degree ofphotoinhibition phenomenon. The two kinds of algae spectral strong absorption tothe band of blue light, but spectral absorption are weak to green and yellow band.The most suitable temperature of276scenedesmus obliquus is20℃. And9chlorella pyrenoidosa, compared with276scenedesmus obliquus adapt to a highertemperature,the most suitable temperature is35℃. Two kinds of algae are suitablefor both neutral and alkaline conditions. photosynthetic oxygen productiondramatically declined When pH is greater than12. The maximum photosyntheticoxygen production rate of9chlorella pyrenoidosa is136.39μmolO₂·mg^-1Chla·h^-1.and to276scenedesmus obliquus the maximum photosynthetic oxygenproduction rate is178.78μmolO₂·mg^-1Chl a·h^-1, has more potential In the oxygengenerating efficiency.（3） Magnetic treatment can improve the algal biomass and production of oxygen. From the production of oxygen effect and economic considerations,logarithmic phase of magnetic treatment is superior to begin from the cultur e at thebeginning of magnetic treatment and disposable magnetic treatment. For276scenedesmus obliquus1000GS around is the maximum promoting function ofmagnetic field.0.5hours of magnetization the oxygen can increase above15%.And9chlorella pyrenoidosa can adapt to a higher intensity of magnetic field. Indifferent magnetic field strength biomass and yield under the action of oxygen areimproved. One hour of magnetization produce oxygen effect best, long time ofmagnetization can not improve the magnetic effect.（4） Experimental results show that the magnetic field has both biologicaleffects and physical chemistry on organic wastewater degradation, Magnetic effectcan improve light transmittance for about5%and wastewater can reduce sewageCOD for35%by biological effect of1000GS magnetic field.（5） With the mixing intensity and temperature increase, release oxygencoefficient increase gradually. Along with the deep heighten and CODconcentration increased, release oxygen coefficient decrease gradually.（6） Outdoor culture experiment showed: Light intensity has a great impact onthe dissolved oxygen of system. In the noon time of sunny day light stress can leadto a downward of dissolved oxygen concentration. So if the light intensity than thelight saturation point, should be conduct shading treatment. Two kinds of algaesuitable culture in different seasons, high temperature stress can lead to276scenedesmus obliquus appeared dissolved oxygen concentration declines "nap"phenomenon in the summer noon. The use of natural light and optical fiber into acombined light source can improve algae light receiving condition, improve thesystem of dissolved oxygen concentration up to20%.