半固化小球藻混养处理压裂返排液的污染物去除及代谢调控机理研究

Wastewater treatment by microalgae has high efficiency and no secondary pollution, and can get biomass sources from wastewater while removing the biodegradable organic pollutants effectively, so it is an ideal technology for fracturing flowback treatment. Because fracturing flowback has lots of contaminants with high toxicity and low degradability, and the coupling mechanism between pollutant removal and microalgae metabolism in fracturing flowback is unclear. Therefore, the scale applications of microalgae in fracturing flowback treatment failed to achieve remarkable achievements. This project intends to study the fracturing flowback treatment by chlorella under semi-cured, tow-step and mixotrophic growth conditions. The main purpose is to analyze the pathway and dynamic theory of organic pollutant degradation by measurement of water quality indexes and characterization of physiological and biochemical activity, research the biologic mechanisms of fat synthesis and accumulation of chlorella, explore the mechanisms of pollutants removal and fats anabolism regulation in fracturing flowback treatment process and the response mechanisms to the stress of toxic and harmful substances, reveal the coupling mechanisms between pollutants removal and fat synthesis and accumulation, clarify the interplay between fracturing flowback treatment and production capacity of chlorella, and lay a theoretical and technical foundation for improving the energy/resource efficiency of fracturing flowback treatment and production capacity of chlorella. The implementation of this project has great significance for the promotion and application of microalgae in fracturing flowback treatment.

利用微藻处理污水效率较高且无二次污染，能够在有效去除污水中难降解有机污染物的同时获得生物质能源，是处理压裂返排液的理想技术手段。由于压裂返排液中污染物成分复杂，返排液中污染物去除与微藻生化代谢的耦合作用机制尚未明确，因此利用微藻规模化处理压裂返排液目前还未能取得显著成效。本申请项目针对基于小球藻半固化、两段法混养的压裂返排液处理过程，通过水质指标测定与生物生理生化活性表征等手段，进行有机污染物降解途径和降解动力学分析以及小球藻脂肪合成与积累的生物学机制研究，努力探索小球藻处理压裂返排液的污染物去除与脂肪合成代谢调控机理以及小球藻对有毒有害物质胁迫的响应机制，揭示返排液污染物去除和小球藻脂肪合成与积累之间的耦合作用机制，明确返排液处理和小球藻产能的相互作用规律，为提高压裂返排液能源/资源化处理效率和微藻产能性能奠定理论和技术基础。项目实施对促进微藻处理压裂返排液技术的推广应用具有重要的意义。

利用微藻处理污水效率较高且无二次污染，能够在有效去除污水中难降解有机污染物的同时获得生物质能源，是处理压裂返排液的理想技术手段。由于压裂返排液中污染物成分复杂，返排液中污染物去除与微藻生化代谢的耦合作用机制尚未明确，因此利用微藻规模化处理压裂返排液目前还未能取得显著成效。本项目结合实验和理论计算手段对小球藻处理压裂返排液开展了深入研究，优化了小球藻半固化处理压裂返排液的培养条件，利用响应面法结合Box-Behnken模型考察了海藻酸钠浓度、氯化钙浓度、交联时间对小球藻生长的影响，得到最优固化条件为：海藻酸钠浓度为2.15%、氯化钙浓度为2.56%、交联时间为17.29h，小球藻藻密度可达1.96g/L。并通过Design Expert软件建立了三种因素与藻密度之间的二次多项回归模型方程，揭示了三种因素交互作用规律。进一步加入活性炭固化小球藻对压裂返排液进行深度处理，利用Box-Behnken模型考察了返排液稀释倍数、β-甘露聚糖酶、活性炭投加量三种因素对处理效果和藻固化生长的影响，得到最优处理条件为压裂返排液稀释倍数为3.96、β-甘露聚糖酶添加量为74.13mg/L、活性炭粉添加量为50mg/L，处理后小球藻藻密度可达2.05g/L，返排液COD去除率可达40.35%。分别建立了三种因素与COD去除率和藻密度之间的二次多项回归模型方程，揭示了三种因素交互作用规律。在小球藻处理返排液的过程中，测定污染物含量和藻细胞密度进行一元线性回归，拟合得到小球藻降解污染物速度的二级反应动力学方程，计算污染物降解半衰期为132.63h，分析了小球藻处理压裂返排液的污染物去除机理。小球藻处理返排液过程中测定藻体生物量、SOD（超氧化物歧化酶）活性、乙酰辅酶A羧化酶（ACCase）活性，分析压裂返排液对小球藻脂肪代谢调控的影响以及小球藻对返排液胁迫耐受情况。综合上述研究结果，深入探讨了压裂返排液的污染物去除和小球藻脂肪合成与积累之间的耦合作用机制。研究结果为提高压裂返排液能源/资源化处理效率和微藻产能性能奠定理论和技术基础，并且对促进微藻处理压裂返排液技术的推广应用具有重要的意义。