| The way purification of sewage using microalgae avoids the disadvantages of high energy consumption ?secondary pollution by the traditional sewage treatment mode, and in accordance with their saving energy, absorbing the advantages of the heavy metals and preparation of bio diesel and other aspects gradually become the hotspot in sewage treatment and energy recovery. However, the algae water separation difficulties has become the bottlenecks in microalgae wastewater treatment and microalgae recovery technology in the engineering application. It is possible to solve the difficult problem of algae water separation by the presence of natural settling microalgae,however, the natural sedimentation of microalgae is often found in the water, so it is the key to select and cultivate the natural sedimentation microalgae as the technology of water purification. In view of which, this topic based on the simulation of the secondary effluent and the actual secondary effluent, through exerts a selective pressure?intermittent drainage? domesticated and screened out two natural settlement of microalgae and explores the different dominant algae of the genus water treatment capacity and cell energy use potential characteristics.By controlling the water exchange volume ratio?VER=0.2, VER=0.5, VER=0.7? of the microalgae reactor under different influent water quality, the high settling performance?sedimentation rate of over 95%? can be cultivated. The domestication experiment results as follows:?1?the wetland water culture system advantage species mainly for large-scale chain Oscillatoria;?2? the artificial water culture system advantage speciess mainly for large-scale linear Diatom.The sedimentation of the wetland system—Oscillatoria system could reach 98% in the culture of 20 cycles,and the artificial water distribution system—Diatom culture was 100% sedimentation rate when the supernatant fluid SS was almost 0g/L. The water treatment circumstance is as follows when different circumstances change water scale:?1? The Oscillatoria system that wetlands water as feed, the NO3--N removal rate are respectively 70%?60% and 50%;?2? the Diatom systems artificial simulation distribution as feed, NO3--N removal rate are respectively 100%?60% and 40%;?3? Under each change water ratio, the average PO43--P was under 0.2 mg·L-1 and removal rate is 95%. Comprehensive comparison between water treatment quality and microalgae sedimentation performance, the screened microalgae under 50% water change ratio is the most conducive to the engineering application.Investigating the microalgal nitrogen,phosphorus utilization,Oscillatoria and Diatom mainly for the biological absorption on nitrogen use.And the degradation of phosphorus, Oscillatoria biological phosphorus removal and chemical phosphorus removal each accounts for about 50%, Diatom biological phosphorus removal accountes for 35% and chemical phosphorus removal pathway accounts for 65%. By increasing the influent nitrogen and phosphorus ratio in water?8:1 to 3:1? to ensure that the phosphate in abundance, the nitrate removal rate of microalgal increases?12.5%?, but it does not be significantly improved. After regular row of algae, when the systems maintain biomass at about 3.0±0.2 g/L, the microalgal activity and the biodegradation rate reaches maximum.Periodic removal of microalgae can be used as a raw material for biodiesel production or sludge co-digestion of the substrate. The components of the lipid, protein and polysaccharide are respectively 6.5%,47%,3.7%,11.2%,41%,6.6%.On this basis, the algae and organic matter total digest of experimental study, microalgae and sludge anaerobic co-digestion, VSS production efficiency of methane per unit mass of diatom were increased by 62.01%?41.44% than Oscillatoria and surplus sludge separate digestion, while Diatom and sludge co-digestion increases by 28.71% and 51.54% than Diatom and sludge separate digestion.And the mechanism research needs to be further explored through experiments. |
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