溶磷菌协同生物滞留设施处理城市降雨径流的磷代谢机制

Traditional bioretention facilities have a great challenge to enhance the phosphorus removal efficiency due to desorption of filler after fixing phosphorus and residual root mineralization of plant after harvesting phosphorus. Moreover, phosphorus-solubilizing bacteria could not discharge sludge after phosphorus uptake, which contributes to the discharge of the phosphorus load with rainfall runoff. To solve the problems, a new process of treating urban rainfall runoff with phosphorus-solubilizing bacteria and a bioretention facility was developed because the phosphorus-solubilizing bacteria shows advantages of dissolution of insoluble phosphides and decomposition of plant residues. The research aims to reveal the mechanism of dephosphorization. Phosphorus-solubilizing bacteria was screened from plant rhizosphere soil and fixed into the filler by carrier-binding method. The effects of phosphorus-solubilizing bacteria on the migration and transformation of phosphorus forms and filler morphology were investigated during rainfall period. Meanwhile, the effect of rainfall runoff scouring on the survival of phosphorus-solubilizing bacteria was also studied. During the rainfall interval, the interaction mechanism between phosphorus-solubilizing bacteria and plant was discussed by using the method of detecting phosphorus-solubilizing bacteria secretion, quantitative analysis of root-shoot ratio and root morphology, and determination of dissolved oxygen concentration around roots. In addition, the influence of phosphorus-solubilizing bacteria on the survival of phosphorus-accumulating bacteria was discussed by using the method of detecting phosphorus accumulating bacteria activity. A kinetic model of phosphorus metabolism in this bioretention facility combined with phosphorus-solubilizing bacteria treating urban rainfall runoff is built during the continuous rainfall period and rainfall interval, and then the parameters were calibrated. The research can provide a quantitative theoretical basis for the efficiency improvement and engineering application of this new technology, and then mitigate the influence of phosphorus discharge from urban rainfall runoff on water environment.

针对传统生物滞留设施处理城市降雨径流时填料固磷后解吸释磷、植物摄磷收割后残留根系矿化释磷、聚磷菌吸磷后无法排泥致使外排径流携带磷负荷等问题，结合溶磷菌解溶难溶性磷化物和腐解植物残体的优势，研发一种溶磷菌协同生物滞留设施处理城市降雨径流新工艺并揭示其除磷机理。从植物根际土壤筛选溶磷菌并利用载体结合法将其固定至填料内部后，在降雨期，考察溶磷菌对土壤层不同形态磷迁移转化方式、填料内外形态的影响，以及降雨径流冲刷对溶磷菌生存的影响。在降雨间隔期，采用溶磷菌分泌物及聚磷菌活性检测、植物根冠比与根系形态定量分析、根系周围溶解氧浓度测定等方法，揭示溶磷菌与植物的互作机制，以及溶磷菌对聚磷菌生存的影响。构建溶磷菌协同生物滞留设施在连续的降雨期与降雨间隔期，处理城市降雨径流的磷代谢动力学模型并进行参数率定，为该新工艺的效能提高和工程应用提供定量理论依据，进而缓减城市降雨径流磷负荷外排对水体环境的影响。

传统生物滞留设施在处理城市降雨径流时，会出现填料固磷后解吸释磷，植物摄磷收割后残留根系矿化释磷，聚磷菌吸磷后无法排泥致使外排径流携带磷负荷等问题。利用溶磷菌解溶难溶性磷化物和腐解植物残体的优势，本项目从植物根际土壤提取溶磷菌，选择包埋法制备溶磷菌微胶囊，并通过微胶囊溶磷试验及菌种鉴定技术，筛选出具有较好溶磷效果的Pantoea菌株。根据海绵城市建设技术指南中生物滞留装置的构造要求，本项目按照一定体积比将溶磷菌微胶囊、填料、潮土混合均匀后填充到土壤层，根据填料种类、植物类型、是否添加溶磷菌，修建八个生物滞留装置。待生物滞留装置修建完成并稳定运行一段时间后，本项目通过检测草酸、磷酸酶、植酸酶和胡敏酸的含量变化，活性无机磷、活性有机磷、微生物结合磷、钙结合磷、铝和铁结合态磷、腐殖酸结合态磷、残渣磷的含量变化，海绵铁、蛭石的形态变化，狼尾草、萱草的根系变化，以及聚磷菌的数量变化，总结出以下结论：溶磷菌代谢过程产生的草酸、磷酸酶和植酸酶，影响土壤中不同形态磷的迁移转化方式，尤其对活性无机磷有显著影响；溶磷菌的引入对填料中难溶性磷结合位点的数量、狼尾草根系平均直径及土壤中聚磷菌的占比有一定的影响。本项目根据降雨期和降雨间隔期监测的不同形态土壤磷数据，构建溶磷菌协同生物滞留设施的磷代谢动力学模型。本项目的研究成果，可为生物滞留设施如何保持长期稳定的运行提供一定的参考和思路。