| The traditional sewage treatment,which is known as primary and secondary treatment,adopted by almost all the sewage treatment plant,showed limited abilities in reducing the inorganic nutrient in the sewage.For example,inorganic nutrient,such as ammonia nitrogen and phosphate cannot be removed effectively only by the primary and secondary treatment before pulling into the river.The third treatment,which is able to decrease the inorganic N and P content easily,is too complex and needs more technology,so most of the sewage treatment plants were unable to support the third treatment.Moreover,this treatment cost too much energy which increases the cost of the treatment.However,inorganic nutrient can be easily and cheaply removed effectively by the help of the microalgae.What is more,the microalgae can not only reduce the inorganic N and P content cheaply,but it can also reuse the nutrient in sewage to reproduce the microalgae.As the researches goes,the sewage can promote the growth of the microalgae,and can produce larger amount of the biomass.The biomass gained in the sewage culture usually contained protein and lipid with good quality and large quantity.So the biomass can be used as industry feedstock and biodiesel feedstock.By using this method,the wasted nutrient in sewage is collected from wastewater and reused as resource.In this study,Chlorella vulgaris FACHB-8 and Scenedesmus sp.FACHB-933 were used to treat artificial sewage dilutions.The sewage used was designed to imitate the real sewage composition and was diluted into 100%,75%,50%,and25% dilutions to find out how different dilutions effected on the microalgae growth and composition.Meanwhile,the BG11 group,which is commonly used in the lab or the factory to grow green or blue microalgae,was set as an negative control group in this study.The growth of the Chlorella vulgaris FACHB-8 and Scenedesmus sp.FACHB-933 and the nutrient composition were analyzed everyday during the culture to analyze the feasible of the sewage culturing the Chlorella vulgaris FACHB-8 and Scenedesmus sp.FACHB-933.And the biomass quality and quantity were also measured after the culture to find out the dilutions affection on the biomass.The Chlorella vulgaris obtained the highest concentration in the 100% dilution sewage,17.940 ×10-6cells / mL,which is much higher than the concentration in BG11 group,5.676×10-6 cells / mL.The results were same when analyzing the growth of Scenedesmus sp.FACHB-933.Scenedesmus sp.FACHB-933 obtained the highest concentration in the 100% dilution sewage,4.120 ×10-6 cells / mL,which is much higher than the concentration in BG11 group,0.940 ×10-6 cells / mL.As the result,the sewage was feasible to culture Chlorella vulgaris FACHB-8 and Scenedesmus sp.FACHB-933 by analyzing the growth data.The concentration of the both microalgae showed positive relations with the dilutions of the sewage.So the 100% dilution was the best culture among the four dilutions by analyzing the data between dilutions.During the culture,the sewage water quality was measured every day to find out the Chlorella vulgaris FACHB-8 and Scenedesmus sp.FACHB-933 abilities on sewage treatment.The removal rates were calculated through the data accessed everyday.The Chlorella vulgaris FACHB-8 gained the COD removal rate between 68% to 85%,the ammonia nitrogen from 32% to 50% and total phosphorus from 55%to 75%.The Scenedesmus sp.FACHB-933 gained the COD removal rate between 83.8% to 92.8%,the ammonia nitrogen from 62.2% to 76.2% and total phosphorus from 36.5% to 85.1%.So the microalgae treatment on the sewage was good.What is more,the quality and quantity of the protein and lipid were promoted highly by using sewage as cultures.Chlorella vulgaris obtained 40.9-50.7 mg/100 mg dry biomass protein in the sewage dilutions,which was higher than the protein obtained in the BG11 group,35.7 mg/100 mg dry biomass.And Chlorella vulgaris biomass contained about 23.4-28.5% of the total lipid,while the BG11 group only contained 22.65%.Similarly,the Scenedesmus sp.performed the same as the Chlorella vulgaris did.The Scenedesmus sp.obtained 45.3-50.0 mg/100 mg dry biomass protein in the sewage dilutions,which was higher than the protein obtained in the BG11 group,37.1 mg/100 mg dry biomass.And Scenedesmus sp.biomass contained about 21.5-25.4% of the total lipid,while the BG11 group only contained 18.2%.In conclusion,sewage is the feasible medium for Chlorella vulgaris FACHB-8 and Scenedesmus sp.FACHB-933,which can promote the quality and quantity of the protein and lipid in the biomass.Meanwhile,the removal abilities of the both microalgae appeared ideal. |
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