| Microalgae-based wastewater treatment has the advantages of low cost,high pollutants removal efficiency,release of O2,and small footprint.However,the wastewater treatment efficiency of microalgae depends on the species and the composition of contaminants in wastewater.Therefore,it was an effective way to enhance the wastewater treatment efficiency of microalgae by screening microalgal strains with excellent growth ability and appropriately regulating the composition of wastewater.In this study,several common green algae were used.They were inoculated into synthetic wastewater with different nitrogen sources to compare the growth characteristics and pollutants removal ability.On this basis,the growth characteristics and pollutants removal ability of the selected algae species in municipal wastewater and cattle farm wastewater were further studied.The main results were as follows:The synthetic wastewater with different nitrogen sources were treated using Chlorococcum sphacosum GD,Chlorella vulgaris,Parachlorella kessleri TY,Scenedesmus quadricauda,Scenedesmus obliquus.C.sphacosum GD and P.kessleri TY had higher growth potential and pollutants removal ability in wastewater with both ammonium and nitrate as nitrogen sources,compared to C.vulgaris,S.quadricauda and S.obliquus.When the nitrogen source was NH4+-N,the maximum biomass of C.sphacosum GD and P.kessleri TY reached 1840 mg/L and 2750 mg/L,and the maximum specific growth rates were 0.643 day-1 and 0.526 day-1 respectively.The removal rates of COD,NH4+-N and PO43--P were 88.43% and 85.45%,91.72% and 92.7%,100% and 100%,respectively.When the nitrogen source was NO3--N,the maximum biomass of C.sphacosum GD and P.kessleri TY reached 3095 mg/L and 2765 mg/L,and the maximum specific growth rates were 0.838 day-1 and 0.822 day-1,respectively.The removal rates of COD,NH4+-N and PO43--P were 98.15% and 97.66%,100% and 100%,94.31% and96.67%,respectively.At the same time,we also found that nitrogen sourceshad a certain impact on the growth and pollutants removal of five microalgae.It was also found that the growth and pollutants removal in wastewater with nitrate was superior to wastewater with ammonium.The p H of the wastewater dropped to 2.63~2.78 when microalgae were cultivated in synthetic wastewater with NH4+-N as the nitrogen source.The acidic p H of wastewater inhibited the growth of microalgae and the removal of pollutants.The municipal wastewater and cattle farm wastewater were treated using C.sphacosum GD.When C.sphacosum GD was inoculated in unsterilized municipal wastewater and cattle farm wastewater,it could grow normally and simultaneously inhibited the growth of bacteria in wastewater.Nevertheless,biomass concentration was low,which was only 456.67 mg/L and 440 mg/L in municipal wastewater and cattle farm wastewater,respectively.The exogenous addition of sodium acetate promoted the growth of C.sphacosum GD.At the end of the cultivation,the maximum biomass of C.sphacosum GD in municipal wastewater and cattle farm wastewater was 596.33 mg/L and 706.33 mg/L,respectively.Before the addition of sodium acetate,the removal rates of NH4+-N,PO43--P and COD in municipal wastewater were45.3%,43.49% and 75.93%,respectively.The removal rates of NH4+-N,NO3--N,PO43--P and COD in cattle farm wastewater were 49.38%,55.86%,24.65% and 55.07%.After the addition of sodium acetate,the removal rates of NH4+-N,PO43--P and COD in municipal wastewater were 98.64%,46.62%and 79.53%.The removal rates of NH4+-N,NO3--N,PO43--P and COD in cattle farm wastewater were 96.61%,92.12%,64.57%,and 57.5%,respectively.It could be seen that the exogenous supplemental carbon source promoted the growth and pollutants removal efficiency of C.sphacosum GD.In addition,at the end of cultivation,the lipid content of C.sphacosum GD cells from municipal wastewater and cattle farm wastewater was 33.2% and20.9%,respectively.Both linoleic acid and linolenic acid were important conpentents of the lipid. |
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