Research On Influencing Factors And Pathways Of Phosphorus Removal By Two Microalgae

In recent years,the phenomenon of water eutrophication has intensified.Phosphorus is an important factor affecting the eutrophication of the water body,and it is much more difficult to remove phosphorus fromwater body than nitrogen.Microalgae can not only remove phosphorus from sewage,but also recover valuable biomass.It is of great significance to study microalgae for phosphorus removal.In this paper,the rapid dephosphorization,biomass yield and micro-pathological characterization of Scenedesmus sp.obtained by laboratory and Chlorella pyrenoidosa CP270,purchased from Freshwater Algae Species Bank,Institute of Hydrobiology,Chinese Academy of Sciences,were studied.The main conclusions are presented as follows:（1）The phosphorus removal efficiencies of the microalgae with different inoculation densities(OD₆₈₀ were 0.1,0.2,0.4 and 0.8,respectively)were similar,and phosphorus removal rates in 24 hours werebetween 71.8%and 79.8%.The results of morphological observation and gene sequencing showed that the microalgae strain was Scenedesmussp.（2）Rapid phosphorus removal of S.sp.in artificial wastewater doubling the concentration of Ca²⁺ and CO₃^2- for 12 hours was studied.Doubling the concentration of Ca²⁺ or CO₃^2- can significantly affect the rapid phosphorus removal process of S.sp.The control group and CO₃^2- doubling experimental group had a faster phosphorus decline process in the supernatant of 2-6 h,and the phosphorus removal efficiencies were 0.21,0.19 mg/（L·h）,respectively.The Ca²⁺ doubling experiment group had a phosphorus decline of 0.30 mg/（L·h） at 4-6 h.（3）The addition of NaAC can significantly promoted the growth of C.pyrenoidosa.From the perspective of cost savings,the addition of 1g/L sodium acetate to municipal wastewater had the best effect on the accumulation of total lipids and biomass,the total lipid productivity was more than 22.08 mg/（L·d）.（4）Different concentrations of Fe³⁺ had different phosphorus removal efficiencies effects on C.pyrenoidosa.The lower concentration of Fe³⁺,the more unstable of the biomass growth and total phosphorus removal,which may be that the chelates formed by Fe³⁺ had a greater effect on phosphorus removal.Different concentrations of Mn²⁺ had a stable effect on phosphorusremoval of microalgae,and the phosphorus removal rateswere more than 90%in the first four days.（5）The results of XRD,SEM and P-element imaging of microalgae powder for 5-day short-term dephosphorization of S.sp.and C.pyrenoidosa showed that the small particles on the surface of microalgae cells were of calcium carbonate crystal structure,but the relationship between the algal phosphorus absorption process and the crystal formation on the surface of microalgae cells needs further study.