The Study On Carbon,Nitrogen And Phosphorus Removal From Aquaculture And Livestock Wastewater By Microalgae

With the rapid development of aquaculture and livestock breeding,the discharge of wastewater has seriously endangered the land environment and human health.Researchers have developed a large number of processes for treatment of aquaculture and livestock wastewater(for example,up-flow snaerobic sludge bed,anaerobic contact process,continuous stirred tank reactor).These processes show excellent performance in the treatment of sewage.Nevertheless,it is difficult to effectively promote the operation of related technologies owing to complex processes and the high requirements for operating parameters.As autotrophic organisms,microalgae have been widely applied to treat the municipal wastewater,and has the advantages of simple operation and high degradation efficiency of pollutants.However,the microalgae-based wastewater treatment technology is rarely applied to the treatment of aquaculture and livestock wastewater,and the pollutants removal efficiency still needs to be further improved.In the present study,five common microalgal species belonging to Chlorophyta were used.Meanwhile,as the two most common types of wastewater in the field of aquaculture and livestock breeding,the aquaculture wastewater and livestock and poultry breeding wastewater were chosen as the water source.We mainly focused on the carbon,nitrogen and phosphorus removal from above wastewater by these microalgae,and the main results were as follows:The aquaculture wastewater from a fishery was treated using Chlorella vulgaris,Chlorococcum sphacosum GD,Scenedesmus quadricauda,Parachlorella kessleri TY and Scenedesmus obliquus.Compared to other three species of microalgae,P.kessleri TY and C.sphacosum GD showed better growth potential and pollutant removal ability.The removal rates of COD,ammonia nitrogen,nitrate nitrogen,nitrite and total phosphorus were 94.44%and 94.44%,98.89%and 98.56%,97.14%and 91.43%,99.80%and 99.47%,98.91%and 97.27%,respectively.It was also found that carbon,nitrogen and phosphorus removal by P.kessleri TY and C.sphacosum GD was enhanced by controlling inoculum concentrations.When the initial inoculation concentration was 100 mg/L,the removal efficiency of COD,ammonia nitrogen,nitrate nitrogen,nitrite and total phosphorus by P.kessleri TY and C.sphacosum GD were 94.44%and88.89%,96.16%and 94.08%,98.95%and 82.86%,94.29%and 97.44%,95.63%and 91.80%,respectively,on the 3~rdd day.Appropriate selection of microalgal species and the control of inoculation concentration of microalgae were conducive to shorten the cultivation period and increase the volumetric loading in the process of microalgae-based aquaculture wastewater treatment once a large amount of aquaculture wastewater was discharged.The cattle wastewater was treated using C.vulgaris,C.sphacosum GD,S.quadricauda,P.kessleri TY and S.obliquus.Compared to other four species of microalgae,C.vulgaris showed the best growth and carbon,nitrogen,phosphorus removal potential.The carbon,nitrogen and phosphorus removal efficiency of COD,ammonia,nitrate,nitrite and total phosphorus were 62.29%,73.23%,98.68%,81.16%,and 85.29%,respectively.The inoculation concentration of C.vulgaris was further optimized to enhance pollutants removal efficiecny.On this basis,two processes“NaClO pretreatment the cultivation of C.vulgaris the cultivation of C.vulgaris”and“NaClO pretreatment the cultivation of C.vulgaris activated carbon absorption”were eastblised to promote the carbon,nitrogen and phosphorus removal efficiency again.Compared to untreated wastewater,the removal efficiency of COD,nitrate,nitrite,ammonia,total nitrogen and total phosphorus were 94.33%and 93.67%,98.61%and 98.10%,100%and 100%,95.47%and 86.69%,95.72%and88.45%,99.44%and 99.09%,respectively.It was obvious that the carbon,nitrogen and phosphorus concentration of effluent met the discharge standards of aquaculture and livestock wastewater.In summary,it is believed that the selection of appropriate microalgal species is very important for wastewater treatment.The efficiency of carbon,nitrogen and phosphorus removal in aquaculture and livestock wastewater can be also improved by the optimization of culture conditions and the combination of related technologies.