再生水滴灌系统灌水器堵塞的微生物学机理及控制方法研究

滴灌因其精量、可控而被认为是再生水最安全、可靠的灌溉方式,然而再生水中含有大量的颗粒物、营养盐分、有机物、微生物等物质使得灌水器堵塞机理变得更为复杂,堵塞风险也大幅度增加。该文在对灌水器堵塞物质-生物膜结构、组分变化特征进行分析,基于生物膜组分:干物质量(DW)、磷脂脂肪酸(PLFAs)和胞外聚合物(EPS)含量与灌水器堵塞程度之间显著的"S型曲线"关系明确了生物膜形成是诱发灌水器堵塞的根本原因。灌水器堵塞过程中表现为:再生水中微生物首先在滴灌系统毛管内部固定形成生物膜,并不断摄取、消耗水中的底物和营养物进行新陈代谢,分泌大量的胞外多聚物,并依靠胞外多聚物的黏性不断吸附微生物及固体悬浮颗粒物而引起生物膜不断形成、生长与脱落以及堵塞沉积物的不断聚集,而最终导致灌水器堵塞。从流道结构形式与几何参数、水体颗粒物特性、近壁面流动剪切力、灌溉水质以及灌水频率五个方面阐述生物膜的形成机制及影响因素。并分别从灌水器流道结构优化(增强流道自清洗能力,促进生物膜脱落)、抗菌材料开发(抑制微生物附着)、化学加氯、微生物拮抗与生长群体响应、微纳米气杀菌等多个角度出发提出了以生物膜形成为靶向目标的灌水器堵塞控制技术体系。最后从滴灌灌水器内部附生生物膜的水动力学-微生物学耦合作用机制研究、滴灌灌水器堵塞预报的综合模拟模型构建及灌水器设计参数合理阈值确定、协同考虑灌水器堵塞清除效应与土壤质量健康长期可持续发展的堵塞控制模式建立三个方面出发提出了再生水滴灌系统灌水器堵塞控制领域未来急需解决的问题。

Microbiology mechanism and controlling methods for emitter clogging in the reclaimed water drip irrigation system

Abstract: Drip irrigation is considered as the most secure and reliable irrigation method for reclaimed water due to its precision and controllability. However, reclaimed water contains a large amount of particles, nutrient salts, organics, micro-organisms and other substances, which makes the emitter clogging mechanism become more complex and also significantly increases the risk of emitter clogging. In this paper, we analyzed the biofilm structure and composition variation characteristics, basing on the significantly "S-curve" relationship between the content of bofilm components: dry weight (DW), phospholipid fatty acid (PLFAs) and extracellular polymeric substance (EPS) and emitter clogging degree, which indicated clearly that the biofilm formation was the original causes to induce emitter clogging. The progress of emitter clogging was performed as follows: microbiology in reclaimed water firstly fixed on the internal lateral surface and formed the biofilm in drip irrigation system, and then continued to absorb, to consume water and nutrient-substrate for metabolism, thus they secreted large amounts of extracellular polymeric substance (EPS), and relied on its sticky characteristics to absorb solid suspended particles and micro-organisms constantly, which induced the formation, growth, as well as shedding of biofilm, and then clogging substances continued to gather, eventually led to emitter clogging. Therefore, the biofilm formation mechanism and its influencing factors were put forward from 5 aspects, which were the flow path structure and its geometry parameters, the characteristics of the water particles, the flow shear force near the wall, the water quality of irrigated water, and the irrigation frequency. After the compositive consideration of the aspects mentioned above, a new integration technology which aimed at holding up biofilm formation in order to control emitter clogging was proposed, which also included different perspectives, including the optimization of emitter flow path structure (enhancing self-cleaning capacity of flow path and promoting biofilm shedding), the development of antibacterial materials (the inhibition of microbial adhesion), chlorination, microbial antagonistic and Quorum-Sensing (QS), micro-nano air sterilization. Finally, several urgent problems needed to be solved in the future for controlling emitter clogging in the drip irrigation using reclaimed water were put forward from 3 aspects: the biofilm inside drip emitter of hydrodynamic - coupling mechanism of microbiology; drip emitter clogging forecasts with comprehensive simulation model and its reasonable emitter threshold determining design parameters, and controlling mode after considering emitter clogging clear synergistic effect and soil long-term sustainability of quality and health.