Tomato Yield and Quality and Emitter Clogging as Affected by Chlorination Schemes of Drip Irrigation Systems Applying Sewage Effluent

Chlorination has been recognized as an efficient and economically favorable method for treating clogging in drip emitters caused by biological growth during sewage application. Further important criteria for determining an optimal chlorination scheme are the different responses of crops to the chloride added into the soil through chlorination. During two seasons in 2008 and 2009, field experiments were conducted in a solar-heated greenhouse with drip irrigation systems applying secondary sewage effluent to tomato plants to investigate the influences of chlorine injection intervals and levels on plant growth, yield, fruit quality, and emitter clogging. Injection intervals ranging from 2 to 8 wk and injection concentrations ranging 2-50 mg L-1 of free chlorine residual at the end of the laterals were used. For the 2008 experiments, the yield from the treatments of sewage application with chlorination was 7.5% lower than the yield from the treatment of sewage application without chlorination, while the yields for the treatments with and without chlorination were similar for the 2009 experiments. The statistical tests indicated that neither the chlorine injection intervals and concentrations nor the interactions between the two significantly influenced plant height, leaf area, or tomato yield for both years. The qualities of the fruit in response to chlorination were parameter-dependent. Chlorination did not significantly influence the quality of ascorbic acid, soluble sugar, or soluble acids, but the interaction between the chlorine injection interval and the chlorine concentration significantly influenced the levels of soluble solids. It was also confirmed that chlorination was an effective method for reducing biological clogging. These results suggested that chlorination is safe for a crop that has a moderate sensitivity to chlorine, like tomato, and can maintain a high level of performance in drip irrigation systems applying sewage effluent.

Effect of drip irrigation method, nitrogen source, and flushing schedule on emitter clogging

Field experiments were carried out at the National Research Center farm, Nubaria area, Behura Governorate, Egypt, to study the effect of nitrogen source, flushing schedule and irrigation method on emitter clogging. Peanut Giza 5 variety (Arachishy pogaea L.) was planted in sandy soil during two successive growing seasons (2010-2011) in the 1st week of May and harvested after 130 days. Treatments used are: 1) two irrigation methods: surface drip irrigation and sub-surface drip irrigation (SDI;SSDI), 2) nitrogen source (NS):NH4NO3, (NH4)2SO4 and Ca(NO3)2 (NS1, NS2 and NS3) and 3) flushing number (FL) 0, 1 and 4 (FL1, FL2;FL3). The experiments design was split-split plot and three replicates were used. Data obtained were subjected to statistical analysis. The main effects of treatments used on clogging per cent could be written the following ascending orders: SDI 3 2 1, NS1 2 3. Concerning the 1st interaction the following ascending orders denote their effects on clogging percent: SDI × FL3 2 1, SDI × NS1 2 3, SSDI × FL3 2 1, SSDI × NS1 2 3, FL1 × NS1 1 × NS2 1 × NS3, FL2 × NS1 2 × NS2 2 × NS3 and FL3 × NS1 3 × NS2 3 × NS3. The differences between any two treatments and/or any two interactions in clogging percent were significant at the 5% level. The effect of the 2nd interaction on clogging percent was significant at the 5% level. The maximum value of clogging (20.18%) and the lowest one (3.9%) were archived in the interactions: SSDI × FL1 × NS3 and SDI × FL3 × NS1, respectively.

Biofilm structure and its influence on clogging in drip irrigation emitters distributing reclaimed wastewater

Using reclaimed wastewater for crop irrigation is a practical alternative to discharge wastewater treatment plant effluents into surface waters.However,biofouling has been identified as a major contributor to emitter clogging in drip irrigation systems distributing reclaimed wastewater.Little is known about the biofilm structure and its influence on clogging in the drip emitter flow path.This study was first to investigate the microbial characteristics of mature biofilms present in the emitters and the effect of flow path structures on the biofilm microbial communities.The analysis of biofilm matrix structure using a scanning electron microscopy（SEM） revealed that particles in the matrix of the biofilm coupled extracellular polysaccharides（EPS） and formed sediment in the emitter flow path.Analysis of biofilm mass including protein,polysaccharide,and phospholipid fatty acids（PLFAs） showed that emitter flow path style influenced biofilm community structure and diversity.The correlations of biofilm biomass and discharge reduction after 360 h irrigation were computed and suggest that PFLAs provide the best correlation coeffcient.Comparatively,the emitter with the unsymmetrical dentate structure and shorter flow path（Emitter C） had the best anti-clogging capability.By optimizing the dentate structure,the internal flow pattern within the flow path could be enhanced as an important method to control the biofilm within emitter flow path.This study established electron microscope techniques and biochemical microbial analysis methods that may provide a framework for future emitter biofilm studies.

Structural Design of a Bionic Anti-Clogging Drip Irrigation Emitter Based on Shark Dorsal Fin

Due to the poor anti-clogging performance of the common drip irrigation emitters, this paper designed a new bionic flow channel in the emitter based on the shape of shark dorsal fin. After preliminary structural design, the computational fluid dynamics (CFD) simulation showed that the bionic emitter exhibited superior anti-clogging performance and reasonable hydraulic performance. The passage rate of particles of the bionic emitter in simulation reached 96.3% which was 37.6% higher than 70% of traditional emitter, and the discharge exponent reached 0.4995 which was close to traditional emitter. Physical experiments were consistent with the CFD results, which confirmed the correctness of simulation. After a short cycle anti-clogging performance experiment, the bionic emitter still maintained 96.09% of the initial flow rate.

Effects of emitter discharge rates on soil salinity distribution and cotton(Gossypium hirsutum L.) yield under drip irrigation with plastic mulch in an arid region of Northwest China

A field experiment was carried out to investigate the effects of different emitter discharge rates under drip irrigation on soil salinity distribution and cotton yield in an extreme arid region of Tarim River catchment in Northwest China. Four treatments of emitter discharge rates, i.e. 1.8, 2.2, 2.6 and 3.2 L/h, were designed under drip irrigation with plastic mulch in this paper. The salt distribution in the range of 70-cm horizontal distance and 100-cm vertical distance from the emitter was measured and analyzed during the cotton growing season. The soil salinity is expressed in terms of electrical conductivity （dS/m） of the saturated soil extract （ECe）, which was measured using Time Domain Reflector （TDR） 20 times a year, including 5 irrigation events and 4 measured times before/after an irrigation event. All the treatments were repeated 3 times. The groundwater depth was observed by SEBA MDS Dipper 3 automatically at three experimental sites. The results showed that the order of reduction in averaged soil salinity was 2.6 L/h 〉 2.2 L/h 〉 1.8 L/h 〉 3.2 L/h after the completion of irrigation for the 3-year cotton growing season. Therefore, the choice of emitter discharge rate is considerably important in arid silt loam. Usually, the ideal emitter discharge rate is 2.4-3.0 L/h for soil desalinization with plastic mulch, which is advisable mainly because of the favorable salt leaching of silt loam and the climatic conditions in the studied arid area. Maximum cotton yield was achieved at the emitter discharge rate of 2.6 L/h under drip irrigation with plastic mulch in silty soil at the study site. Hence, the emitter discharge rate of 2.6 L/h is recommended for drip irrigation with plastiic mulch applied in silty soil in arid regions.

Essentials of Drip Irrigation System for Saving Water and Nutrients to Plant Roots: As a Guide for Growers

Many regions around the world are characterized by limited water resources, where the average annual per capita renewable water is about 1000 -1700 cubic meters. For instance, in china the problems of water supply are widely known globally. Though, China is facing main problem which is how to distribute water, instead of water shortage in itself. Therefore, restricted resources of water are increasingly stressed in the future by many factors such as excessive clouds of water, pollution and climate change. On the other hand, most studies have been indicated that the agricultural sector is one of the sectors that will face a large water deficit in the future due to the high demand for food, competition for water resources, drought and the high consumption of water due to the acquisition of traditional surface irrigation techniques. In spite of introduce modern irrigation methods such as drip irrigation in agriculture by developing irrigation methods and eliminating old traditional irrigation methods, however, its efficiency is related to the qualifying of farms and users of irrigation water, where they are the main users of irrigation water in water resources management. The considerable challenge facing agriculture is to raise irrigation efficiency depending on water-saving irrigation systems to provide water resources for crops. Therefore, the purpose of this study was to provide farmers with important points about using drip irrigation technology, to raise their technical level in using irrigation water, through their guidance to the best techniques and to avoid some common mistakes in design, utilization, management and maintenance of drip irrigation system.

Field Performance Evaluation of a Small-Scale Drip Irrigation System Installed in the Upper West Region of Ghana

This study was conducted to evaluate the water application uniformity for a drip irrigation system, considering the water quality and the duration of usage. The uniformity parameters, Emission Uniformity (EU %) and Uniformity Coefficient (UC %) were determined for the drip irrigation system installed over a year of performance. The procedures are based on taking measurements of emitter discharge along selected driplines on a sub-main. The catch can be identified as L1A, L1B, L1C, L1D, same for L2A to L2D, L3A to L3D and L4A to L4D. This gave a total of sixteen (16) measurement positions as there were 4 driplines. Results indicated that the uniformity of water application was 90% indicating that the emitter was still good after a year of installation. The average discharge rate was 0.57 l/h. The uniformity coefficient (UC %) for the gravity-fed drip irrigation system was 78%, indicating good water application and was quite significant for the evaluation of the uniform distribution of water for the design. The expansion of this irrigation method in rural communities could contribute to relevant water savings in most areas of the Upper West Region of Ghana.

Experimental study on calculation model of labyrinth emitter discharge under subsurface drip irrigation

For different texture of soils,the grain composition is different with significant changes.Since the emitter of subsurface drip irrigation(SDI)is buried in the soil,emitter discharge is influenced by soil properties.An experiment was conducted to investigate the relationship between the soil properties with emitter working pressure and emitter discharge of SDI.Selecting three different grain composition soils,and emitter working pressure,as well as soil clay content,soil bulk density and initial soil moisture content respectively as influence factors of emitter discharge of SDI,the experimental scheme was gained by uniform design.A calculation model for determination of the SDI emitter discharge was established by regression analysis with the first two kinds of soil test data,and its reliability was verified by the third kind of soil test data.The model is simple with high accuracy,easy to use,and lays the foundation to study hydraulic elements of SDI field network,especially taking the soil clay content as an influencing factor has widened the scope of application of the model.The achievement is of great significance for design and management of SDI.

HYDRAULIC CHARACTERIZATIONS OF TORTUOUS FLOW IN PATH DRIP IRRIGATION EMITTER

At present, the tortuous emitter has the most advanced performances in drip irrigation. But the theories and methods for designing its flow path have been strictly confidential and the researches on the function of practical guidance have seldom been published. Seven types of most representative tortuous emitting-pipes currently used in agricultural irrigation regions of China were chosen for investigating the geometric parameters of the flow path by means of combining high-precision microscope and AutoCAD technology. By the measurement platform developed by the authors for hydraulic performances of emitters, the free discharge rates from the 7 types of emitters were measured at 9 pressure levels of 1.5 m, 3.0 m, 5.0 m, 7.0 m, 9.0 m, 10.0 m, 11.0 m, 13.0 m and 15.0 m. Then the discharge-pressure relationship, manufacturing variation coefficient, average velocity on the cross-section of flow path and the critical Reynolds number for the flow regime transformation within the paths were analyzed in detail. The results show that both pressure-ascending work pattern and pressure-descending work pattern have some impacts on the discharge rates of tortuous emitters, but the impact level is not significant. The target pressure could be approached by repetitive applications of the two work patterns during pressure regulation. The operation under low pressures has some impacts on the hydraulic performances of emitters, but the impact level is also not significant. The classical model of the discharge-pressure relationship is suitable for the pressure range of 1.5 m -15.0 m. The Reynolds number for fluids within the 7 types of tortuous emitters ranges from Re=105 to Re =930. The critical Reynolds number for the flow regime transformation is smaller than that for the routine dimension flow path. The variation coefficient of emitter discharge rates is slightly fluctuating around a certain value within the whole pressure range.

FLOW CHARACTERISTICS IN ENERGY DISSIPATION UNITS OF LABYRINTH PATH IN THE DRIP IRRIGATION EMITTERS WITH DPIV TECHNOLOGY

The energy dissipation mechanism and anti-clogging properties of drip irrigation emitters are closely related to flow characteristics of the fluid in its flow paths, and flow field tests using modem flow visual technologies were carried out by a large number of designers. The Digital Particle ImageVelocimetry （DPIV） system was built for un-disturbed flow tests in the labyrinth path. In this article, the flow field was measured in the flow path section, the structural unit and the local region near sawtooth. Under the pressure level of 10 Kpa, 50 Kpa, 100 Kpa and 150 Kpa, the flows in the two labyrinth paths were in the turbulence state, with flow stagnation regions and whirlpool regions in the structure of the labyrinth path sections. The flow stagnation regions should be eliminated as much as possible. But the vortex should be fully developed, which could increase the self-cleaning capacity and the anti-clogging capacity of the emitter. With respect to the anti-clogging performance and the energy loss efficiency of the emitter, the M-type flow path is better than the K-type flow path.

高含沙水滴灌灌水器堵塞机制及防堵技术研究进展

为解决黄河水中粒径小于0.10 mm细小泥沙颗粒引发的滴灌灌水器堵塞问题。通过文献调研,回顾了高含沙水滴灌条件下灌水器物理堵塞机制相关研究进展,并提出了进一步研究方向。细小泥沙颗粒含量较高的浑水滴灌时,滴头堵塞主要是含沙量、泥沙粒径与颗粒级配耦合作用的结果。滴灌系统工作条件如工作压力的动态变化有助于移除流道内黏、粉等细颗粒堵塞物质,促进较大泥沙颗粒排出流道;灌溉水温越高,滴头抗物理堵塞性能越强;对浑水加气和磁化处理可改变毛管内水流水力特性及悬浮泥沙运动规律,增强水流拖拽力,减小管道内泥沙淤积量。此外,施肥增强了水体中泥沙颗粒间的絮凝作用,对浑水水肥一体化滴灌滴头堵塞具有明显加速作用。浑水含沙量、粒径和颗粒级配是引发滴头物理堵塞的重要因素,确定易引发滴头堵塞的敏感含沙量、颗粒粒径段,选用适宜肥料种类和施肥浓度阈值,优化滴灌系统工作条件参数是改变毛管内泥沙颗粒运移和沉积规律、延缓滴头堵塞进程、提高水肥一体化滴灌水肥利用效率的有力措施;采用统一的灌水试验方法,充分利用现代测试手段,结合生产实际有针对性地改进工程技术处理措施是解决滴头堵塞问题的必要途径。

沼液滴灌条件下不同类型灌水器的堵塞特征

为了探求不同类型灌水器在沼液滴灌中的抗堵塞性能,研发适用于沼液滴灌的灌水器,明确沼液滴灌条件下灌水器的堵塞类型。选用内镶贴片式灌水器(1.38、2、3 L/h)、内镶圆柱式灌水器(2、3 L/h)、压力补偿式灌水器(2、4、6 L/h)三类灌水器,在灌水压力0.08 MPa、水沼液配比4∶1(体积比)条件下进行周期性间歇灌水试验,比较不同灌水器的堵塞情况,并使用扫描电镜分析堵塞物的粒径大小及各粒径占比情况,同时结合堵塞物的傅里叶红外光谱图分析堵塞物的组成成分。结果表明,8种灌水器(E1~E8)达到堵塞标准所需的时间分别为108、126、141、111、132、84、102和117 h;灌水器堵塞物在出水口、进水口以及过水流道内均有分布,进水口处为黄色泥沙沉积,出水口及过水流道拐角处为黑色絮状物;堵塞物成分为沙粒、碳酸盐、硫酸盐、磷酸盐等无机化合物以及烃类、蛋白质、脂类等有机物;堵塞物中88.42%的颗粒物粒径集中在0.2~1.4μm的粒径范围内,其余11.58%为大絮状物。综上所述,同类型灌水器中,额定流量越大的灌水器达到堵塞标准所需的时间越长,抗堵塞性能越好;同额定流量的灌水器,内镶贴片式灌水器的抗堵塞性能最佳;额定流量3 L/h的内镶贴片式灌水器的抗堵塞性能最佳;灌水器发生的堵塞类型为物理-化学-生物三者协同作用导致的复合型堵塞。

滴灌系统叠片过滤器结构参数优化

针对不同级配含沙水和灌水器类型的叠片过滤器结构选型问题,该研究选取常用叠片过滤器,通过组合不同叠片数量改变相邻叠片间孔径,设计了多种不同泥沙处理能力的过滤器。对5种泥沙粒径级配条件下5种孔径叠片过滤器的性能开展试验研究,根据不同工况下叠片过滤器运行周期内的水头损失、堵塞时段水头损失增长速率、过滤器的堵塞均匀度以及灌水器流量偏差率等指标,采用模糊数学综合评价方法,构建综合考虑灌溉含沙水、叠片过滤器和滴灌灌水器的多目标评价模型。结果表明:基于叠片孔径可调的过滤器可以实现拦截不同粒径范围泥沙的目标,5种孔径过滤器拦截泥沙粒径(拦截率大于90%的沙粒段中最小粒径级配的中值粒径)分别为49、82、100、127和150μm;随着过滤器孔径减小,粒径越细小的含沙水对水头损失增大作用越显著。不同级配含沙水和灌水器类型条件下叠片过滤器性能综合评价结果与试验结果相符,通过对综合评价指标值排序,筛选出灌溉含沙水、过滤器、灌水器三者最优的匹配方式,能够同时实现灌水器堵塞程度轻微和过滤器性能稳定。提出的叠片过滤器结构参数配置决策方案,可为叠片过滤器的合理配置和使用提供参考。

微纳米加气对再生水滴灌灌水器堵塞的影响

为研究再生水滴灌时水中加入微纳米气泡对灌水器堵塞的影响,选用4种不同类型的灌水器,设置再生水不加气、再生水加气2个处理,以平均流量比(Dra)表征灌水器堵塞的发展程度,以克里斯琴森均匀系数(Cu)、统计均匀系数(Us)评价随试验运行时间推移滴灌系统的均匀性变化.结果表明:微纳米加气对再生水滴灌系统灌水器堵塞具有显著影响,相较于不加气处理,加气处理下4种灌水器(E1,E2,E3,E4)的Dra值分别提高了16.2%,24.4%,18.2%和22.1%;加气处理下各灌水器的Cu和Us值大于不加气处理;加气对不同类型灌水器堵塞的控制效果也存在一定的差异,微纳米加气可降低灌水器的堵塞风险,延缓堵塞程度,延长灌水器的使用寿命,且对整个滴灌系统的均匀性有积极影响.试验结果可为再生水滴灌和加气滴灌技术的推广应用提供一定的技术支撑.

2种土壤地下滴灌滴头流量变化规律及对入渗空腔的响应

为研究入渗空腔对地下滴灌滴头流量和土水势的影响规律,通过土箱试验和数值模拟相结合的方法,对比分析了黏土和壤质砂土2种土壤灌水过程中土壤正压及滴头流量的变化规律,反演了滴头出口处空腔半径,并建立了黏土中空腔半径的计算模型.研究结果表明:相同条件下,壤质砂土中的滴头流量大于黏土中的,但变化幅度小于黏土中的;壤质砂土中土壤正压随时间变化呈上升趋势,黏土中土壤正压随时间变化呈下降趋势,受空腔影响,滴头流量与土壤正压随时间的变化趋势不存在必然关系.模拟中,壤质砂土入渗空腔半径可选择较小值或认为与滴头出口半径相同.黏土中空腔半径随滴头额定流量和容重增大而增大.相对于选用固定值,研究得到的空腔半径可以提高现有计算公式在求解滴头流量和土壤正压的精度,拟合的空腔半径经验模型可以应用于地下滴灌水力设计,同时为土壤水分入渗数值模拟的边界条件设置提供依据.

引黄滴灌不同含沙率对灌水器堵塞影响和试验研究

灌水器堵塞是影响黄河水滴灌灌水质量的关键因素。对8种不同灌水器与1‰(1 kg/t)、2‰(2 kg/t)、4‰(4 kg/t)3种含沙率进行模拟试验,重点研究了引黄滴灌不同类型滴灌灌水器的流量变化规律和堵塞效应。试验结果表明:灌水器的流量衰减率随着灌水历时的增加而增大,灌水300 h后衰减率整体达到43%~72%;流量衰减率随着含沙率的增加而增大,低泥沙含量时(1‰),75%的灌水器呈现中度堵塞情况,高泥沙含量时(4‰),100%的灌水器呈现重度堵塞。灌水器N-1.6与N-2.0B在3种不同含沙率下的灌水均匀度均达到80%以上,可以满足作物的灌溉需求。灌水器的流量衰减与灌水器的流道长度呈正相关,随着流道长度的增加,灌水器抗堵塞性能降低,流量衰减率增大。流道内沉积泥沙的中值粒径与灌水器设计流速呈负相关,随着设计流速的增加而减小。灌水器流道内0~30μm粒径的沉积泥沙体积比随含沙率的增加而不断降低。研究成果可为解决引黄滴灌灌水器堵塞问题提供参考。

分叉角与回转半径对双向流道灌水器水力性能影响模拟研究

为研究双向流道灌水器水力性能,将其结构单元作为研究对象,以分叉角和回转半径两个结构参数为影响因素,采用正交试验设计16种结构参数组合方案,利用计算流体动力学软件Ansysfluent对流道内部流体的流动状态进行数值模拟,通过量纲分析建立流道结构参数与流道单元局部水头损失的回归模型。结果表明:双向流道单元局部水头损失与分叉角、回转半径和流道流速有关,分叉角与局部水头损失呈负相关关系,回转半径和速度与局部水头损失呈正相关关系;当入口流速为固定值时,分叉角为32.4°、回转半径为1.72 mm,流道单元局部水头损失最大;当设置10个流道单元时,交叉排列方式组合的灌水器流态指数较优。

引黄滴灌系统灌水器堵塞机理及措施研究进展

黄河水中含有大量的泥沙颗粒、微生物和有机物等,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,随着滴灌形式的多功能转变,对灌水器的抗堵塞能力提出了更高的要求。为了探索适宜引黄灌区滴灌系统灌水器堵塞问题的解决方案,本研究通过对灌水器堵塞物质来源与特征组分进行分析,系统梳理了灌水器堵塞的主要影响因素、灌水器发生堵塞的特性,并提出了缓解灌水器堵塞的主要方法,如控制水源水质、优化灌水器结构、应用微生物拮抗技术等。最后,基于引黄灌区的地域特性提出了其未来研究方向的相关建议,旨在为解决灌水器堵塞问题提供理论基础,有效推动黄河流域滴灌技术的大面积应用和滴灌系统的高效安全运行。

黄河淤背区地表温度与滴灌灌水器内腔水垢形成相关性研究

黄河下游淤背区种植有适生林和草皮等作物,且部分采用了滴灌方式,在每年6—8月高温时期,林地滴灌工程在非滴水时间段4~8 d期间,铺设在地面的聚乙烯(PE)塑料毛管上的滴头内腔中存在未流出的剩余水,在蒸发过程中不可避免地形成水垢,经过多年积累,最终可能形成堵塞。通过开展对地面温度、水质等资料的收集及现场观测等工作,运用相关成果资料,初步揭示了淤背区滴灌地表土壤温度与滴头内腔水垢形成之间的关系,提出相应的解决措施。

Flow Behaviour Analysis and Experimental Investigation for Emitter Micro-channels

The existing research of the flow behavior in emitter micro-channels mainly focuses on the single-phase flow behavior.And the recent micro-particle image velocimetry（PIV） experimental research on the flow characteristics in various micro-channels mainly focuses on the single-phase fluid flow.However,using an original-size emitter prototype to perform the experiments on the two-phase flow characteristics of the labyrinth channels is seldom reported.In this paper,the practical flow of water,mixed with sand escaped from filtering,in the labyrinth channel,is investigated.And some research work on the clogging mechanism of the labyrinth channel＇s structure is conducted.Computational fluid dynamics（CFD） analysis has been performed on liquid-solid two-phase flow in labyrinth-channel emitters.Based on flow visualization technology-micro-PIV,the flow in labyrinth channel has been photographed and recorded.The path line graph and velocity vector graph are obtained through the post-treatment of experimental results.The graphs agree well with CFD analysis results,so CFD analysis can be used in optimal design of labyrinth-channel emitters.And the optimized anti-clogging structures of the rectangular channel and zigzag channel have been designed here.The CFD numerical simulation and the micro-PIV experiments analysis on labyrinth-channel emitter,make the ＂black box＂ of the flow behavior in the emitter channel broken.Furthermore,the proposed research promotes an advanced method to evaluate the emitter＇s performance and can be used to conducting the optimal design of the labyrinth-channel emitters.