Effect Of Nitrogen On Nitrogen And Phosphorus Removal And Flocculation Characteristics For Self-flocculating Microalga Chlorococcum Sphacosum GD

Microalgae for wastewater treatment have advantages of low energy consumption,carbon dioxide fixation,oxygen release and biomass production.However,microalgae cells are difficult to be separated from wastewater,which restricts the engineering application of microalgae-based wastewater treatment.Therefore,the combination of wastewater treatment and efficient separation of microalgae is the key to promote the engineering application of microalgae-based wastewater treatment.The aim of this study is to investigate effects of nitrogen sources and nitrogen concentrations on the growth,pollutants removal and self-flocculation properties of Chlorococcum sphacosum GD.The purpose of the research is to find out the optimal nitrogen source and nitrogen concentration,which promotes the growth,pollutants removal and self-flocculation of C.sphacosum GD.At the same time,the pilot cultivation of C.sphacosum GD with optimal nitrogen source and nitrogen concentration has also been done to evaluate the performance of C.sphacosum GD in the actual environment.The main results are as follows:The growth,pollutants removal,self-flocculation property and oil accumulation of C.sphacosum GD were affected by nitrogen sources(nitrate nitrogen,ammonia nitrogen and organic nitrogen).The growth and the flocculation of C.sphacosum GD in nitrate nitrogen wastewater were the best.By the end of culture,the biomass increased to 234.83 mg/L,and the flocculating efficiency was up to 85.78% within 3 h settlement.C.sphacosum GD cultivated with ammonia nitrogen had excellent removal efficiency of COD,ammonia nitrogen and phosphorus,which were up to 91.85%,98.99% and 41.45%,respectively.C.sphacosum GD cultivated with organic nitrogen accumulated high levels of neutral lipids.Ammonia nitrogen concentration(10,20,30 and 50 mg/L)had a certain effect on the growth,pollutants removal,self-flocculation property and oil accumulation of C.sphacosum GD.The biomass reached 190.09 mg/L at the end of culture when C.sphacosum GD was cultivated in wastewater with 20 mg/L ammonia.Pollutants removal efficiency was also the best under 20 mg/L ammonia concentration,which was up to 92.84%,98.84% and 69.29%,respectively.C.sphacosum GD cultivated with 50 mg/L ammonia had the excellent flocculating efficiency of 80.39%.C.sphacosum GD cultivated with 10 mg/L ammonia accumulated high levels of neutral lipids.C.sphacosum GD was cultivated in wastewater with 20 mg/L ammonia in pilot-scale reactor outdoor.At the end of culture,the biomass of C.sphacosum GD gradually increased to 200 mg/L and the removal efficiency of COD,ammonia nitrogen and phosphorus reached 87.33%,99.06% and 82.15%,respectively.The flocculating efficiency gradually decreased from 66.67% to 21.41%.Besides,the neutral lipid content of C.sphacosum GD decreased by 59.31%.