纳米气泡对沼液滴灌系统灌水器的防堵塞效应与机理

沼液中含有大量的微生物、盐分离子与固体颗粒物等致垢物质，极易导致沼液滴灌系统灌水器物理-生物-化学复合堵塞，纳米气泡凭借其比表面积大、表面带负电荷、吸附性能高等特点，有望成为一种协同控制沼液灌溉系统复合型污垢的可靠方法。该研究旨在探究纳米气泡（Nanobubbles，NBs）对沼液滴灌系统灌水器复合型堵塞的缓解效应，明确NBs对灌水器附生生物污垢、化学沉淀和颗粒污垢的控制效果。将无NBs水和饱和NBs水进行不同体积配比，配置了3种NBs浓度的灌溉水：对照组（无NBs水）、饱和NBs水（全部为NBs水）、半NBs水（体积比1∶1），分别对3种内镶片式灌水器开展试验。结果表明：与对照组相比，NBs有效地缓解了灌水器堵塞，系统运行末期3种类型灌水器内部堵塞物质的干质量分别降低了22%～49%、18%～41%和25%～47%，而滴灌系统的相对平均流量和克里斯琴森均匀系数整体提高了15%～44%和26%～48%。NBs有效地控制了灌水器附生的生物污垢、化学沉淀和颗粒污垢形成，使得堵塞污垢中胞外聚合物的含量降低了29%～53%，碳酸盐、磷酸盐等化学沉淀的含量降低了52%～75%，而颗粒污垢的总量降低了35%～68%。相比而言，饱和NBs水处理比半NBs水处理下污垢的干质量减少了21%，建议在沼液滴灌工程中采用饱和NBs的方式来缓解灌水器堵塞。该研究证明了NBs是一种有效且生态友好型的防灌水器复合堵塞技术，有助于沼液滴灌技术的进一步推广。

Effects and mechanism of using Nanobubble to inhibit biofouling and scaling in biogas slurry drip irrigation emitters

Abstract: Biogas slurry irrigation can effectively alleviate the shortage of agricultural water and fertilizer resources as well as the environmental pollution caused by improper discharge, and the nutrient elements in biogas slurry can improve the yield and quality of crops. However, biogas slurry contains a large number of microorganisms, salt ions, particulate matter and other scaling substances which are easy to cause the irrigation system of drip irrigation clogging, which has become a key obstacle to the application and promotion of biogas slurry drip irrigation technology. Nanobubbles (NBs) with an average diameter of less than 200 nm are characterized by large specific surface area, negative surface charge and high adsorption performance and are expected to be a reliable method for synergistic mitigation of compound fouling in biogas slurry irrigation system. The purpose of this study was to explore the mitigation effect of nanobubbles on the composite clogging of the emitter of the biogas drip irrigation system, and to clarify the mitigation effect of NBs on the epiphytic fouling, chemical precipitation and particle fouling of the emitter. Different volume ratios of NBs-free water and saturated NBs water were prepared, and three kinds of irrigation water with NBs concentrations were configured: control group (non-NBs water), saturated NBs water (all NBs water), and half NBs water (1:1). The clogging mitigation test was carried out for three kinds of inner insert type emitter device respectively. During the experiment, Relative Average discharge (Dra) and Uniformity coefficient (CU) of the emitter are calculated. At 112.5, 225, 337.5, 450, 562.5, 675, 787.5 and 900 h, the dry weight in the emitter was recorded. The Extracellular Polymeric Substances (EPS) was calculated at 225, 450, 675 and 900 h. Polycrystalline diffraction patterns and mineral composition of the clogging material were determined. The results showed that, compared with the control group, NBs effectively relieved the clogging of the emitter, and the dry mass of the clogging substances in the three types of emitters at the end of the system operation decreased by 22%-49%, 18%-41% and 25%-47%, and increased the Dra and CU of the drip irrigation system by 15%-44% and 26%-48%, respectively. Meanwhile, NBs significantly decreased the biofouling, chemical precipitation and particulate fouling adhering to the emitter. Among them, the content of EPS in the dirt was reduced by 29%-53%, the content of precipitate such as carbonate and phosphate was reduced by 52%-75% respectively, while the total amount of particulate fouling was reduced by 35%-68%. In contrast, the dry weight of foulants in the 0:1 treatment was 19% lower than that in the 1:1 treatment. It is recommended to use saturated NBs in the biogas drip irrigation project to alleviate the clogging of the irrigator. This study proves that NBs is an effective irrigation clogging mitigation technology, which is helpful for the further promotion of biogas drip irrigation technology.