Deep Purification Of Urban Sewage By Nannochloropsis Sp.

Water pollution and energy crisis had become a major hinder to sustainabledevelopment of China’s economy, so the development of clean and renewable energyhas become the focus. Biofuel as an alternative to fossil fuels is more successful typeof fuel currently in the world that has been promoted. Microalgae become an idealraw material of large-scale production of bio-diesel because of higher photosyntheticefficiency. However, the raw material of algae biodiesel costs accounted for75%ofGDP, so it made a lot of solutions to solve the problem of raw materials for biodiesel,including the use of urban secondary effluent or marine aquaculture culturingmicroalgae, culturing microalgae on the land which is not suitable for cultivation ofplants, fixed integrated of microalgae biodiesel production and flue gas, high-valuenew bioproducts, etc. Among these solutions, the use of sewage culturing microalgaecan significantly reduce the nitrogen and phosphorus content in the water, reducingthe sludge discharge, saving water and nutrient consumption, and bio-dieselproduction provides cheap materials, so not only can compensate for the high cost ofmicroalgae production of oil shortage, but also produce good environmental benefits,it can be a new solution ideas of the current water shortage and lack of energyprovides.In this study, firstly, a marine microalgae was isolated from the Qingdao coastaland have been identified to explore the feasibility of using this algae deep purificationof sewage and the water, then the effect of different concentrations of metal ions onalgae growth and fat accumulation have been analysised, thus the wastewater hasbeen treated and the optimal conditions synchronous cultures of microalgae wasobtained. Then the algae was inoculated into sewage of three sterilized different toanalysis the growth and fat accumulation of microalgae and its purifying effects ondifferent sterilization of sewage effluent, while PCR-DGGE and DNA sequencingmethod were used to study microbial community structure changes during the cultivation process of microalgae and analyze the impact of bacteria on algae growthand purification effects on sewage.Identified by morphological and molecular biology, the isolated microalgae wasNannochloropsis sp. Algae can adapt well in the sewage environment and the celldensity can be achieved4.55×106cells/ml. While comparing to urban wastewater,the growth and lipid accumulation in recycled water was not worse. The removalability of the algae on water nitrogen and phosphorus in wastewater was well,especially the removal of ammonia and orthophosphate, removal rate up to95.69%and93.92%respectively.Fe3+can be a good promotion of the growth of Nannochloropsis sp., the best Fe3+concentration that was the most beneficial to growth and liquid accumulation was36μmol/L, the maximum cell density was up to9.94×106cells/ml. While the effectsby Zn2+on lipid accumulation of microalgae intends to be more remarkable, theoptimal Zn2+concentration for lipid accumulation of microalgae was2.4μmol/L.Adding Fe3+, Zn2+to sewage has no adversely effects on removal of nitrogen andphosphorus from wastewater by algae.After using three different sterilization treated sewage to cultureNannochloropsis sp., it can be found that microalgae removal of nutrients focused ontraining the beginning2-8days, then content of nitrogen and phosphorus change in alesser extent; After32days, nitrogen, ammonia nitrogen, nitrate nitrogen and totalphosphorus content was12.66mg/L,0.47mg/L,0.27mg/L,0.09mg/L in the sewage,the removal rate reached up to81.2%,98%,97.67%and95.63%. During training,the three sewage maximum cell density reached2×106,1.8×106,1.7×106cells/ml,grease algal cells into the stable period begins to accumulate. Thus, Nannochloropsissp. has strong ability to adapt sewage, growing well in wastewater, sewage andremoval effect of nutrients nitrogen and phosphorus is obvious. Especially inautoclaved sterilization wastewater, the algal cell density, nitrogen and phosphorusremoval rates are significantly higher than the other two treatments, except there isnot much difference between the accumulation of oil and filter sterilized.Using the methods of PCR-DGGE analysis and DNA sequencing, bacterial community structure was analyzed which were from different growth period ofmicroalgae. The results showed that Proteobacteria and Firmicutes were the. Algaeculture wastewater of autoclaved sterilization contained less microbial species,dominant bacteria strains were obvious; In the three treatments wastewater, microbialdiversity has decreased as time goes on, and duiring the training processmicroorganisms were certain changes.