Study On The Microalgal Cultivation And Removal Of Nitrogen And Phosphorus Cultivated In Anaerobically Digested Effluent From Kitchen Waste Diluted With Campus Sewage

With the continuous improvement of living standards for people,the consumption of energy gradually increased and the energy shortage has become the major problem at present.At the same time,sewage is rich in nitrogen,phosphorus and other nutrients,if handled improperly or untreated into the water will lead to eutrophication and a series of environmental problems.Therefore,looking for a new type of renewable energy and remove nutrients in the sewage efficiently were the two difficult problems we are facing at present.In order to solve the two problems of water pollution and energy shortage at the same time,a new type of coupling system about cultivating microalgae using sewage to produce biomass and dealing with sewage simultaneously is widely used.The method could not only reduce the cost of microalgal cultivationbut also remove the nutrients in the water effectively andhave both environmental benefits and economical benefits.Anaerobically digested effluent from kitchen waste?ADE?diluted with campus sewage?CS?was used to cultivate Chlorella sp.SDEC-18 in this study.The optimum dilution factor,microalgal growth and nitrogen and phosphorus removal ability were also explored.Calculate the cost savings and choose the optimum dilution factor to promote the utilization of ammonium by changing cultivation method.The main conclusions in this paper are as follows:?1?Anaerobically digested effluent from kitchen waste?ADE?diluted with campus sewage?CS?was used to cultivate Chlorella sp.SDEC-18.The growth of microalgae cultivated in different dilution times for wastewater were better than that in BG11 medium.SDEC-18 in 1%medium obtained the maximum biomass concentration 0.4 g/L,the biggest growth rate 105.5 × 10^-3 d^-1 and the maximum biomass yield 25.8 mg/L/d.The results showed that it was feasible to use ADE diluted with CS instead of the traditional BG11 medium to cultivate SDEC-18 and the optimal dilution ratio was 1%.?2?The lipid contentof Chlorellasp.SDEC-18 in all the culture medium was higher than 25%.From the transmission electron microscopy of microalgae,SDEC-18 could regulate the biochemical activity of their cells and increase the intracellular lipid droplets to maintain cell growth in order to adapt to the unfavorable environment of high ammonia concentration.And the highest lipid content 38.65%and lipid productivity 11.79 mg/L/d of SDEC-18 were obtained in 10%medium.The lipid content and lipid productivity of the microalgae in BG11 medium were 29.48%and 5.53 mg/L/d respectively.The composition of the fatty acid methyl ester ofChlorellasp.SDEC-18 obtained in different media showed that the biodiesel obtained was of high quality.?3?It is possible to save a lot of cost by using ADE diluted with CS instead of BG11 medium to cultivate SDEC-18.If a ton of SDEC-18 algae powder cultivated in BG11 medium was necessary,367500 yuan were needed.Therefore,this alternative method can save a lot of cost andwas feasible.Chlorellasp.SDEC-18 could grow well in mixed wastewater and tolerate ammonia concentration of 284.6 mg/L,which has the advantage of tolerating unfavorable environment.And the optimum removal efficiency of TN and NH₃-N was only 33.6%and 40.5%in 1%medium,respectively.?4?The 1%medium was selected as the experimental group using bioreactor and the method of aeration.The biomass concentration was 1.58 g/L after 24 days of culture and the highest chlorophyll a content of SDEC-18 was about 35.0 mg/L accounting for 3.2%of algal dry weight.The lipid content was 27.6%and the lipid productivity was 18.2 mg/L/d.The removal efficiency of TN,NH₃-N and TP was high,and the removal efficiencies were 94.7%,98.6%and 99%respectively,and the effluent reached the national A discharge standard for comprehensive wastewater discharge standards.