低温对高浓度人尿液废水培养小球藻的影响

Effects of low temperature on Chlorella cultivation in high-concentration human urine wastewater

针对寒区气温低,微藻培养过程加热能耗大的问题,以蛋白核小球藻Chlorella pyrenoidosa和普通小球藻Chlorella sp为试验藻种,利用人工气候培养箱,在人尿液废水添加比例40%条件下,研究2种小球藻在15.0、17.5、20.0、22.5、25.0℃较低温度下的生长特性和小球藻蛋白质含量,以及培养液中营养物质的利用情况。结果表明,2种小球藻均可以在高浓度尿液废水中生长,蛋白核小球藻Chlorella pyrenoidosa对各试验组培养液中总氮、氨氮、总磷和化学需氧量(Chemical Oxygen Demand,COD)的平均去除率分别达到78.02%、79.59%、79.31%、20.11%,最大生物量达到0.502 g/L;普通小球藻Chlorella sp对培养液中总氮、氨氮、总磷和COD的去除效果更好,平均去除率分别达到87.90%、89.55%、89.29%、68.66%,最大生物量达到1.007 g/L。2种小球藻对低温的响应均呈现随温度的升高生物量和培养液中相关指标的去除率也随之增大的趋势,但不同温度区段的变化率存在差异,温度为20.0℃及以上时变化较小,温度低于20.0℃时变化较大。并且在微藻培养各指标中,微藻的生物量和蛋白含量,以及培养液中的COD含量变化较大,而培养液中的总氮、氨氮、总磷的变化规律差别较小。普通小球藻Chlorella sp对低温的耐受特性明显优于蛋白核小球藻Chlorella pyrenoidosa,普通小球藻Chlorella sp更适合在低温条件下用于高浓度尿液废水的处理和资源化。该研究为寒区微藻的低耗高效培养和尿液废水的资源化利用提供理论支持。

Microalgae(microscopic algae)have been the most promising renewable energy sources in freshwater and marine systems,due to the short growth cycles,high photosynthetic efficiency,environmental adaptability,and cellular lipid content.The cultivation cost of commercial microalgae is ever increasing in recent years.Particularly,chemical reagents are generally added to supply the nutrient sources for microalgae growth.Fortunately,human urine wastewater can be expected for microalgae cultivation,due to the abundant nitrogen,phosphorus,and trace elements for microalgae growth.Microalgae biomass can also be obtained to reduce the microalgae cultivation cost after purification,in order to realize the resource-based and high-value utilization of human urine wastewater.In the case of the microalgae growth temperature above 25.0℃,it is very important to explore the microalgae suitable for the low-temperature culture,in order to reduce the heating energy consumption of microalgae culture in winter in the north of China.In addition,human urine is also currently sterilized for microalgae cultivation,due to the high dilution times.More wastewater can be produced from a small amount of original human urine,leading to the high pretreatment cost of microalgae cultivation.In this study,a systematic investigation was carried out to clarify the effects of different temperatures(15.0,17.5,20.0,22.5,and 25.0℃)on microalgae cultivation using human urine diluted by low times.The Chlorella pyrenoidosa and Chlorella sp were selected as the microalgae species.An artificial climate incubator was used under the human urine addition ratio of 40%and light intensity of 4000 lx for 14 days.The results showed that the two types of Chlorella grew better in the high concentration of human urine wastewater.The average removal ratios of the total nitrogen,ammonium nitrogen,total phosphorus,and chemical oxygen demand in the culture solution of Chlorella pyrenoidosa reached 78.02%,79.59%,79.31%,and 20.11%,respectively,where the maximum biomass dry weight reached 0.502 g/L.Comparatively,the average removal ratios of the total nitrogen,ammonium nitrogen,total phosphorus,and chemical oxygen demand in the culture solution of Chlorella sp.reached 87.90%,89.55%,89.29%,and 68.66%,respectively,where the maximum biomass dry weight reached 1.007g/L.There was an increase in biomass production and the total nitrogen,ammonium nitrogen,total phosphorus,and chemical oxygen demand removals of Chlorella pyrenoidosa and Chlorella sp.,as the increase of temperature(P<0.05).The increasing rates were smaller under the temperature of higher than 20.0℃than those lower than 20.0℃.Meanwhile,there was a strong influence of low temperature on the microalgae biomass,Chlorella protein,and chemical oxygen demand removal ratio than that on the contents of total nitrogen,ammonium nitrogen,and total phosphorus.Better adaptability of Chlorella sp.was also achieved in the human urine at low temperature than that of Chlorella pyrenoidosa,indicating more suitable for cultivation in the north of China.This finding can lay a theoretical foundation for the low-consumption and high-efficiency culture of microalgae in cold regions.