Lication Of Urine And Municipal Wastewater In Microalgae Cultivation

Microalgae has been widely used in energy, pharmaceutical and chemical fields due to its rapid growth rate, high photosynthetic efficiency, carbon fixation ability and valuable bioactive substances. The enormous consumption of water resource and nutrients during culture becomes the bottleneck of a large-scale production of microalgae biomass. Domestic wastewater could provide water and nutrients for microalgae growth with a win-win of water purification.If urine, a major source of nitrogen and phosphorus in domestic wastewater, could be source-separated, the process of sewage treatment can be simplified. Secondary effluents still contains nitrogen, and phosphorus, and the further removal remains difficulty. Therefore, applying urine and urban secondary effluents in microalgae culture, can not only reduce the cost of biomass production, but also recycle the nutrients in wastewater.With growth rate, biomass and protein contents as an indicator and the growth in Zarrouk medium served as the control, a growth evaluation of Spirulina platensis cultivated in human urine was made. Nutrients were added to the urine in order to improve the culture condition. However, municipal wastewater was firstly pretreated by electrodeionization process, and the concentrated solution obtained was used for cultivation of Spirulina platensis. Besides, the effect on microalgae growth by adding different nutrients was investigated.In batch culture, Spirulina platensis was able to grow in diluted urine and the growth rate increased as the dilution ratio increased. But the biomass, growth rate and protein contents of Spirulina platensis cultured in urine were lower than that cultured in Zarrouk condition due to the ammonia inhibition in initial culture stage and lack of nutrients in later period of culture. During the training, the nitrogen, phosphorus and organic matters was directly utilized by87-95%,74-77%and50-60%, respectively. It was found that the most suitable inoculation volume was10%with an initial absorbance value (OD560) of0.1-0.18. Subsequently, to improve culture conditions in urine, a semi-continuous culture by adding Zarrouk medium, carbon sources and nitrogen sources was conducted. On the basis of batch culture, the urine was added to the culture medium after7days and a part of the original medium was used for repeated culture. When R, the renewed volume to the total volume, was0.8, almost no growth lags were observed with highest growth rate achieved in repeated cultivation. This provided a basis for large-scale cultivation.It was found that the wastewater from secondary sedimentation was not suitable for direct culture of Spirulina platensis. Concentrated solution obtained by electrodeionization technology can be directly used for the cultivation of Spirulina platensis, but the growth rate and biomass obtained were lower than that in Zarrouk medium. Zarrouk medium, NaHCO3, NaNO3and trace elements were added to the concentrated solution in order to improve culture condition. The maximum of growth rate (0.193d-1) and biomass concentration (1.60g/L) was obtained by adding50%Zarrouk and6.0g/L NaHCO3,2.0g/L NaNO3, respectively. Combined the cost with effects,20%of the original algae solution could be directly inoculated to the concentrated solution for production, or adding6.0g/L NaHCO3and1.0g/L NaNO3to concentrated solution could be used to optimize culture condition. During incubation,99.1%ammonia and84.6%TP in concentrated solution was recovered, respectively. Besides, a protein content of56.8%in microalgae was obtained.