Emitter Clogging Research Articles

PERFORMANCE EVALUATION OF HYDRAULIC PARAMETERS OF A DEVELOPED DRIP IRRIGATION SYSTEM

Experiment was carried out in the department of Agricultural and Bioresources Engineering, during the period of August to October, 2017. The hydraulic performance of a developed drip irrigation system was assessed. The experimental work was conducted on field with irrigated field area of 7 m x 3 m and lateral spacing was 0.35 m. Sixty (60) hospital drip sets (given sets) were used for the experiment as improved emitters. Volumetric method was used to determine application rate (PR) and emitters discharge. The emission uniformity, emitter flow variation, co-efficient of uniformity and co-efficient of variation were determined accordance with the equations described by the American Society of Agricultural Engineering (ASAE). Soil chemical properties were determined accordance with the American Public Health Association (APHA). The findings revealed that the soil in the area is classified as sand clay loam and normal soil. Results indicated that the mean and standard deviation of the emitters were 9.639 L/hr and 0.07 L/hr respectively. There were no emitters clogging. The emitter flow variation was 2.5 % and less than 10 % which was desirable range, while coefficient of variation was 0.07 and less than 0.11 which was marginal. The application rate was 17 mm hr-1 which was within the recommended range of 15 – 25 mm hr-1. The emission uniformity and coefficient of uniformity were 99.4% and 99.2% respectively, which shows that the system was well-designed. This finding indicated that hospital drip sets proved to the high quality. Therefore, it can be used as standard emitter.

Effect of different sand filter underdrain designs on emitter clogging using reclaimed effluents

Sand media filters are those that achieve a higher retention of organic and inorganic solids, which is why they are usually recommended when reclaimed effluents are used in drip irrigation systems. Sand filters usually differ on the design of their underdrain, where an important pressure drop is produced. However, the effect of the design of sand filter underdrain on emitter clogging has not been widely studied. Three sand media filters with different underdrain designs (collector arms, inserted domes and drainage with porous media) were used for filtering a reclaimed effluent in a surface drip irrigation system. Pressure-compensating emitters with 2.3 l/h nominal emitter discharge were placed every 40 cm in 4 irrigation laterals each measuring 90 m in length. Effluents were chlorinated after being filtered. The filters operated for 1000 h with sand media heights of 20 and 30 cm and filtration velocities of 30 and 60 m/h. At the beginning, after 500 h, and at the end of the experiment the emitter discharge of each one of the 2712 emitters that were installed was experimentally measured under field conditions. On average, there was a statistically significant reduction (p < 0.05) on emitter discharge regarding the initial value of 8.03% at 500 h and 10.84% at 1000 h. Emitter clogging was primarily affected by the interactions between underdrain design, emitter location and irrigation time. Differences on emitter discharge due to underdrain design were only observed at 1000 h, showing a significantly higher flow rate (p < 0.05) those emitters protected with the filter with a collector arm underdrain, despite the fact that this filter did not achieve the highest turbidity removals. Emitter location had also a significant effect after 500 h of operation, being discharge significantly lower (p < 0.05) only in the last 2 m of the laterals, with the minimum values found for the final two drippers. The three filters used in the experiment did not show a significant effect on the percentage of completely clogged emitters, which mainly depended on the interaction between irrigation time and emitter location.

Effects of Urea Fertigation on Emitter Clogging in Drip Irrigation System with Muddy Water

AbstractIn this study, 10 test cycles of fertigation with urea using muddy water were performed to examine the anticlogging performance of inline nonpressure-compensating emitters. The potential ca...

Assessment of Field Water Uniformity Distribution in a Microirrigation System Using a SCADA System

Microirrigation is an efficient irrigation technique, although when wastewater is used the probability of operation problems such as emitter clogging increases. In most of microirrigation systems, control of irrigation performance is manual and sporadic, therefore clogging problems may not be detected at the right time. As it is easier to prevent emitter clogging if it is detected earlier, close monitoring of pressure and flow rates in microirrigation systems is an important way to achieve microirrigation system requirements and accomplish higher irrigation efficiencies. A supervisory control and data acquisition (SCADA) system was used to monitor and control the performance of three microirrigation subunits; each one with four laterals, 90 m long with 226 emitters. The SCADA system monitored the pressure and flow across the irrigation laterals, and distribution uniformity coefficients were determined in real time, as they are indexes commonly used for evaluating drip irrigation systems. Results were compared with those experimentally obtained, showing a good correlation; although the emitter position had an important effect on the computed values. This work shows that a SCADA system can be easily used to continuously assess the pressure and water distribution uniformity without carrying out time-consuming manual field assessments.

Socio-Economic Characteristics and Problems Faced by Apple Cultivators Under with Drip and without Drip Irrigation System

Apple is the main fruit crop of Himachal Pradesh and is grown in nine out of the twelve districts. It contributes to 40 per cent of the fruit growing areas in Himachal Pradesh. A sample of 60 farmers cultivating apple was selected using multistage simple random sampling. Out of 60 farmers 30 farmers are with drip irrigation and 30 farmers are without drip irrigation. Literacy situation revealed that 93.37 per cent family members were literates with a literacy index of 3.37 in case of with drip irrigation farms. In case of without drip irrigation farms, 91.61 per cent family members were found literates with a literacy index of 3.05. Average size of land holding was 1.34 and 1.38 ha on with drip and without drip irrigation farms, respectively which is low due to more area under apple. Area under apple has been found to be 64.35 per cent out of total cultivated land on with drip irrigation farms and in case of without drip irrigation farms it was 67.09 per cent out of total cultivated land. The main problems of farmers with drip irrigation were clogging of emitters (83.33%), difficulty in inter cropping and high cost of spare parts (66.67%) each and irregular electric supply and spare parts not available at village (63.33%) each. The main problems of farmers without drip irrigation were high cost of establishment (86.67%), lack of knowledge on subsidy (73.33%) and lack of technical knowledge (70.00%).

Different operation patterns on mineral components of emitters clogging substances in drip phosphorus fertigation system

The operation patterns of drip irrigation fertigation system have significant impacts on the emitter clogging. Exploring the dynamic variation and influence mechanism of mineral components in clogging substances under different operation patterns can provide suitable guidance for fertigation management models. In this study, an emitter clogging experiment was conducted through three operating irrigation patterns (once per day, OP1/1; once every 4 days, OP1/4; once every 7 days, OP1/7) by running high-sediment surface water under the potassium dihydrogen phosphate (PDP) fertigation. The X-ray diffractometer was used to identify the mineral components. The results indicated that the primary mineral components in the emitter clogging materials were quartz, silicate, and carbonate and their contents accounted for more than 97% of the total. The components showed a dynamic process of slow growth followed by rapid growth. And there was a significant correlation between mineral compositions and the clogging degree (R2 > 0.86). The application of PDP fertilizer did not generate phosphate precipitation in the emitters directly, but accelerated the carbonates precipitation through adsorption influence of phosphate fertilizers instead. The contents of quartz, silicate, and carbonate were at their highest levels in OF1/7 followed by OP1/4, and then at their lowest in OP1/1 due to the difference time of applying P fertilizer time in three operating patterns. Both the relative discharge (Dra) and uniformity coefficient (CU) of the drip emitters also showed similar trends for the all eight types of emitters that were tested in this experiment.

Lateral flushing with fresh water reduced emitter clogging in drip irrigation with treated effluent

Emitter clogging is a persistent problem for drip irrigation using treated effluent. To find an effective flushing regime, research was conducted using two water types (treated effluent and fresh groundwater) with two flushing frequencies (every irrigation event and every five irrigation events) and a control (no flushing). Thin-wall laterals with inline-labyrinth emitters were examined. The irrigation duration was 1 h daily for 91 days. Emitter discharge was monitored. At the end of the study, the mean emitter discharge decreased about 9% in the treated effluent treatment, 7–8% in the fresh water treatment and 13% in the control treatment. Flushing was effective in preventing sediment accumulation, and using fresh water reduced emitter clogging better than using treated effluent. But there were no significant differences between the two flushing frequencies. Flushing with fresh water reduced the calcium and magnesium deposits of the emitter, and the changeable water environment discouraged the bacteria growth. Therefore, when treated effluent is used for drip irrigation, emitter clogging should be controlled by flushing with fresh water every five irrigation events.

English

A prototype of a real-time closed loop automatic control system has been successfully developed to suit trickle irrigation systems management. The control system was designed to manage the irrigation system based on collecting data through soil moisture sensors located at three different locations acting each third of the lateral to put the effect of emitters&rsquo; flow rate variation along laterals on soil moisture content distribution in consideration. Soil moisture content which will be used to start and stop the irrigation process will be based on the average of three sensors&rsquo; readings. Required inputs to manage the irrigation system were soil field capacity (FC), permanent wilting point (WP), and percentage of moisture allowed depletion (MAD). Irrigation process will begin when the soil moisture content equals the desired percentage of available water and it will stop after reaching soil field capacity. The system was provided with ability to check some defects that are related to the irrigation system like clogging, poor uniformity, and water pumping failure. Laboratory assessment showed that the control system has applied the design considerations and is expected to save irrigation time if implemented with low or poor uniformity trickle irrigation networks when compared to high uniformity networks. The study recommended evaluating the effect of this control system implementation in field especially with trickle irrigation networks which show poor uniformity to use the potentials of the control system to predict emitter clogging, and poor uniformity which are mostly appear in such irrigation systems. Key words: Automatic control, closed loop, flow rate variation, modern irrigation systems, real time. &nbsp

Using an anti-clogging relative index (CRI) to assess emitters rapidly for drip irrigation systems with multiple low-quality water sources

Drip irrigation is considered as one of the most suitable methods to utilize multiple low-quality water sources. However, the emitter clogging issue caused has become the main constraint for its application and promotion, which possibly leads to system failure if it becomes uncontrollably acute. How to select the anti-clogging emitter product precisely, in order to improve the system functionality and extend the service life, is the premise of increasing the sustainability of drip irrigation systems broadly used for agriculture and landscape irrigation. Therefore, drip irrigation emitter clogging experiments using three types of low-quality water sources (including water with high sediment and salinity loads and their mixture with the same volume ratio) were conducted. Under the fourteen working conditions included in the present study, the discharge variation rate (Dra), Christiansen coefficient of uniformity (CU) and emitter clogging substances (ECS) of the referenced emitter all showed linear correlations with the other eight types of emitters used in this paper, and the regression slopes were referred to as the anti-clogging relative index (CRI). The relative magnitudes of CRI_Dra, CRI_CU and CRI_ECS could effectively represent the anti-clogging abilities of different emitters. Instead of being affected by the different working conditions or water quality parameters, the differences in CRI were mainly due to the emitter structural characteristics. Two dimensionless parameters of emitter flow paths (W/D and A1/2/L) were significantly correlated to the relative magnitudes of CRI, and thus these two parameters directly allowed for assessing of the anti-clogging ability of emitters. The model established could provide an accurate method for the selection of anti-clogging drip emitter products in a rapid way, which is beneficial for the safe, high-efficiency and long-time running of the drip irrigation system using low-quality water sources.

Variation of microorganisms in drip irrigation systems using high-sand surface water

Using high-sand surface water in agricultural irrigation has become an alternative way to release groundwater stress. Although drip irrigation is considered as the most appropriate irrigation method for high-sand water application, as it is precise and controllable, it easily leads to emitter clogging. The clogging issue couldn’t be well controlled if merely focused on the sand size and concentration. Therefore, figuring out whether microorganisms significantly affect the clogging process is important for appropriate high-sand water utilization. Based on these, the phospholipid fatty acids (PLFAs) was applied as the biological indicator of the microorganisms, and an in-site drip irrigation experiment using eight types of flat emitters was carried out. The results indicated that there were more than 10 types of PLFAs in emitter clogging substances using high-sand water, brackish water and their 1:1 mixed water in volume. As PLFAs contents showed significant positive linear correlations with emitter clogging degree (CD) (R2>0.89, p<0.05), it demonstrated that microorganism variations directly affected emitter clogging process. Among the PLFAs obtained, Pseudomonas 16:0 and heavy pyrolysis hydrogen Bacillus 18:0 were the PLFAs those fully distributed during the clogging process, which occupied 66.0%–87.0% of the total contents of PLFAs, and they both displayed significant linear correlations with CD(R2>0.72, p<0.05). Therefore, they were considered as the critical bacteria to emitter clogging. Their competition and the effects on the other types of PLFAs determined the evolution and variation characteristics of the microorganism community, and the ecological parameters of microorganism community (including diversity, evenness and dominance indexes) all had significant quadratic patterns with CD (R2>0.56, p<0.05). Although mixing high-sand water and brackish water in equal volume reduced both the sediment and salinity in the water source, the PLFAs obviously increased and resulted in the more intense biological clogging process and thus enhanced the physical-chemical-biological coupling effects. Consequently, the operating cycle of mixed water treatment decreased by 8.9%–22.0%. The results in this paper aim to provide theoretical references to drip irrigation emitter clogging mechanism using high-sand surface water and to offer guidelines for appropriate high-sand water utilization in agriculture.

DESOBSTRUÇÃO DE EMISSORES COM ÁCIDO FOSFÓRICO EM FERTIRRIGAÇÃO COM CLORETO DE POTÁSSIO VERMELHO

Estudos na área da irrigação têm sido realizados com o objetivo de se racionalizar a utilização da água na agricultura. Um dos problemas mais comum nos sistemas de irrigação por gotejadores é o entupimento de emissores. Desta forma, o objetivo deste trabalho foi utilizar o ácido fosfórico como agente de limpeza de tubos gotejadores sob fertirrigação com cloreto de potássio vermelho. Assim este estudo utilizou um sistema de quimigação de tubos gotejadores conduzidos por gravidade, porém mantendo-se a pressão de entrada com baixa variação, em quatro tratamentos experimentais: irrigação antes da quimigação (T1); fertirrigação com cloreto de potássio vermelho (T2); quimigação com ácido fosfórico (T3); e irrigação depois da quimigação (T4), com seis repetições e tempo médio de uma hora por repetição. Os tratamentos que fertirrigaram soluções em uma concentração de KCl com 60% de potássio foram desobstruídos com ácido fosfórico em uma concentração de 7,086 g L-1, sendo esta operação analisada por coeficientes de uniformidade, gráficos de controle estatístico e mapas de contorno. Observou-se que no manejo de não abrir os finais de linha, os resíduos provenientes da desobstrução causaram um grau de entupimento de 15,13% em média nas linhas dos tubos gotejadores. Os resultados mostraram que o ácido fosfórico pode ser utilizado como agente de limpeza em tubos gotejadores, porém requer manejo adequado do sistema.

Effects of Drip Irrigation Frequency on Emitter Clogging using Saline Water for Processing Tomato Production

AbstractAs an important parameter of drip irrigation using saline water, irrigation frequency not only affects crop growth by changing the soil moisture–salinity distribution, but also influences the anti‐clogging performance of the drip irrigation system by changing fouling growth inside emitters. Hence, a representative medium‐salt‐tolerant crop of processing tomatoes was selected as the research object. The effects of different drip irrigation frequencies (S1 (1‐day irrigation interval), S2 (2‐day irrigation interval) and S3 (4‐day irrigation interval)) on the clogging characteristics of emitters were analysed via a 2‐year drip irrigation experiment using saline water between 2013 and 2014. The results showed that the discharge ratio variation (Dra) and the Christiansen uniformity coefficient (CU) of the emitters decreased as the irrigation interval increased, while there was a negative linear correlation between Dra and the irrigation interval (R2 &gt; 0.79). The highest Dra and CU values of 80.9 and 78.0% were observed in high‐frequency irrigation (S1) after 2 years of planting. Moreover, clogging fouling inside the emitter accumulated gradually and exhibited a significant positive linear correlation with irrigation interval time (R2 &gt; 0.80). The chemical components of clogging fouling, which were calcium magnesium carbonates, quartz, silicates, and sodium chloride, were the same under different irrigation frequencies. The emitter clogging of drip irrigation systems using saline water for processing tomato production in the Hetao irrigation area presented a composite clogging (mainly chemical clogging associated with physical clogging). Considering previous research, a high frequency of once per day is recommended for drip irrigation using saline water. © 2019 John Wiley &amp; Sons, Ltd.

Mechanism of intermittent fluctuated water pressure on emitter clogging substances formation in drip irrigation system utilizing high sediment water

Emitter clogging is one of the bottlenecks that restricts the application and promotion of drip irrigation technology. Applying intermittent fluctuated water pressure is regarded as an effective way to overcome drip irrigation emitter clogging when using high sediment water. Therefore, a drip irrigation experiment using Yellow River water was carried out at Deng Kou County, Inner Mongolia, China, to study emitter clogging controlling effects of three fluctuation patterns. The control group (CG) operation pressure was 40 kPa, and three intermittent fluctuated water pressure modes were 40 kPa + fluctuating water pressure for 1 h (FP1 h), 2 h (FP2 h), and 4 h (FP4 h), respectively. The system was fluctuated once every 16 h, and the amplitude of the fluctuating water pressure was 80–100 kPa with a cycle of 40 s. The characteristics of the sediment size and mineral components of clogging substances found in emitters and laterals were also analyzed. The results showed that intermittent fluctuated water pressure not only directly changed the flow velocity distribution in the emitter flow path to reduce the deposition of clogging substances, but also controlled the formation of clogging substances inside the laterals to avoid enhanced emitter clogging by transporting into the emitter. The intermittent fluctuated operating pressure could effectively reduce contents of emitter clogging substance in drip irrigation, and the longer period it was applied, the better controlling effect was observed. Comparing with the CG, applying intermittent fluctuated water pressure with constant period of 4 h would reduce the total clogging substance contents by 26%. The clay and powder particles were reduced by 56% and 34%, respectively. Meanwhile the quartz, silicate, calcium magnesium and carbonate in the clogging substances decreased by 36%, 35%, and 11%, respectively. Thus, the discharge ratio variation coefficient (Dra) and Christiansen Uniformity coefficient (CU) increased by 10.1–16.7% and 8.9–14.2%, correspondingly. These results could provide references for the application and promotion of drip irrigation technology using water with high sediment load.

Composite fouling of drip emitters applying surface water with high sand concentration: Dynamic variation and formation mechanism

Drip irrigation applying surface water with high sand concentration leads to a higher risk of composite fouling, which is the most complex material type of clogging. Thus, understanding the dynamic variation and formation mechanism of composite fouling is the prerequisite for controlling clogging substance and establishing rational anti-clogging method to promote high-sand surface water for drip irrigation. In this paper, the components of the composite fouling were studied through the emitter composite fouling experiment under three drip irrigation frequencies. The results indicated that the particulate fouling composition (solid particle, SP), crystallization fouling composition (CaCO3 and MgCO3 precipitate, C-MP), and biofouling composition (extracellular polymeric substance, EPS, and microbial activity, MA) grew as the system operated. Significant positive linear correlations were obtained among different compositions (R2>0.82, p < 0.01), and the microorganism attached on the surface of SP and continuously secreted EPS mutually promoted the formation of biofouling and particulate fouling. The condensation of microcrystals formed by C-MP with SP promoted the formation of crystallization and particulate fouling, and phosphorus anions enhanced flocculation and agglomeration between particles. Thus, physical-chemical-biological reactions occurred to promote mutual growth, which ultimately led to composite fouling formation. Meanwhile, various components in the composite fouling increased gradually with higher operating frequency, which could aggravate the emitter clogging and decrease the relative discharge of the drip irrigation emitters (Dra) and the uniformity coefficient (CU).

Factors Influencing Emitter Clogging Caused by Negative Pressure in Potted Yunnan Laterite with Root-Zone Infiltration Irrigation

Abstract. In this study, an equivalent mechanical model was established for the clogging induced by soil suction under negative pressure during root-zone infiltration irrigation in a crop-free pot, and a state diagram was plotted for the clogging process induced by a single soil suction factor under negative pressure. Three groups of impact factor experiments were conducted using three different emitters: a flow-adjustable emitter with eight horizontal outlets (emitter L), a flow-adjustable emitter with two vertical outlets (emitter Q), and an anti-clogging material wrapped around the outer surface of emitter L (emitter K). The first group of experiments investigated the influence of irrigation pressure, the variation of irrigation pressure (range of 0.02 to 0.12 MPa), and the amount of sediment inside emitter L in Yunnan laterite. For the second group of experiments, two soil types (Yunnan laterite and yellow sand), two single-event irrigation volumes (170 and 250 mL), and two numbers of irrigation events (8 and 16) were used to quantitatively analyze the sediment content in emitter L. The third group of experiments used emitters L, Q, and K and involved quantitative analysis of the clogging differences in the different emitter types with two soil types (Yunnan laterite and yellow sand) and two numbers of irrigation events (24 and 64). Statistical analysis showed that irrigation pressure, soil type, irrigation pattern, and emitter type were significant (p &amp;lt; 0.05) for the amount of sediment due to negative suction inside the emitter. The results demonstrate that emitter clogging induced by negative pressure tends to first decrease and then increase with increasing irrigation pressure. The amount of sediment that accumulates within an emitter is influenced by both the soil suction effect under negative pressure as well as soil flushing under positive pressure. Within emitter L, clogging induced by soil suction under negative pressure was more likely to occur when using Yunnan laterite rather than yellow sand soil. When both soil types were used in the test, emitter L was observed to be more prone to clogging induced by negative pressure compared to emitter Q, whereas emitter K exhibited the best anti-clogging performance. This study provides a quantitative account of the factors associated with clogging induced by negative pressure, and it provides a theoretical and experimental basis for gaining an in-depth understanding of emitter clogging during root-zone infiltration irrigation in Yunnan laterite. Keywords: Emitter, Negative-pressure clogging, Pot environment, Root-zone infiltration irrigation, Yunnan laterite.

Dynamic effects of chemical precipitates on drip irrigation system clogging using water with high sediment and salt loads

Introducing low quality water to micro irrigation system comes up with higher risk of emitter clogging and affects its practical applications in fields. Assessment of major components growth process of clogging substances and its influence on clogging to reveal the clogging mechanism become unavoidable. A drip irrigation experiment with four irrigation and flushing treatments was conducted to study the chemical precipitates dynamic variations of chemical precipitates in clogging substances. 8 types of flat emitters subjected, and clogging samples were collected when emitter clogging degrees reached 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, respectively. X-ray diffractometer was applied to identify the mineral components. The results showed that both chemical and physical clogging occurred in all 4 operation modes and the primary chemical precipitates such as quartz and silicate (muscovite, alkali feldspar, chlorite and carbonate, dolomite, calcite) were found in emitter clogging substances. At the end of the experiment, their quantity accounted for more than 98%. Flushing treatment would slow down the accumulation of clogging substances in emitters. Although mixing these two water sources in same volume was equal to reduce the sediment and salinity concentrations to a half, the clogging degrees did not reduce as much as expected. On the other hand, positive linear correlations were observed between all three kinds of chemical precipitates and the clogging degrees, in which relative radius (A1/2/L) and mean velocity of flow path cross-section (v) showed significant impact, and thus affected the dynamic growth of chemical precipitates in clogging substances.

Influence of Dentation Angle of Labyrinth Channel of Drip Emitters on Hydraulic and Anti‐Clogging Performance

AbstractThe geometric parameters of labyrinth channels play an important role in the hydraulic and anti‐clogging performance of drip emitters. In this study, the flow fields, individual representative sands and sand groups in the labyrinth channel of emitters, with dentation angles of 90°, 60°, 45° and 30°, were firstly simulated using a computational fluid dynamics discrete element method (CFD–DEM) of coupling. Particle tracking velocimetry (PTV) was used to trace individual representative sands. The numerical results were verified with clear water hydraulic performance tests and muddy water anti‐clogging performance tests. The results suggest that the discharge coefficient and flow exponent declined when the dentation angle of the labyrinth channel was reduced. A large number of sand groups were observed to enter the vortex areas and move in a circular manner. The time it took for particles to pass through the labyrinth channel lengthened when the velocity decreased and as a result, the probability of emitter clogging increased. Therefore, by using a recommended angle range of 90° to 60° and a combined higher hydraulic performance level, emitters were less likely to clog. It was a novel approach to adopt a CFD–DEM coupling method to conduct numerical analysis of individual sand particles and sand groups in the investigation of emitter anti‐clogging issues. The findings will increase the design efficiency of flow channels and will save human and material resources. © 2018 John Wiley &amp; Sons, Ltd.

HYDRAULIC PERFORMANCE OF DRIPPERS APPLYING SANITARY LANDFILL LEACHATE DILUTED IN WATER

ABSTRACT Drip irrigation with diluted sanitary landfill leachate favors the development of grasses on the landfill surface, however, the clogging of emitters of the irrigation systems is the major obstacle for this practice. The objective of this study was to select empirical models of the Christiansen's uniformity coefficient, distribution uniformity coefficient, and statistical uniformity coefficient of drip irrigation sets applying sanitary landfill leachate diluted in water as a function of time of operation, and quality of the effluent. An experiment was conducted in a completely randomized experimental design with three replicates, using a split-split plot arrangement, with operating pressures (70, 140, 210, and 280 kPa) in the plots, types of drippers (G1, 1.65 L h-1; G2, 2.0 L h-1; and G3, 4.0 L h-1) in the subplots, and operating time of the drip irrigation sets (0, 20, 40, 60, 80, 100, 120, 140, and 160 hours) in the sub-subplots. Data regarding hydraulic performance and effluent quality were acquired every 20 hours during 160 hours of operation and subjected to simple and multiple regression analyses. The G3 dripper operating at pressures of 70 and 140 kPa were the combinations that best attenuated biofilm clogging. The linear regression and square root were the models that best represented the reduction in the uniformity of the effluent application as a function of the operating time of the drip irrigation sets. The linear correlations denoted that calcium contents and total coliform population rates were the characteristics of the sanitary landfill leachate that most affected the drip clogging process.

Formation mechanism for emitter composite-clogging in drip irrigation system

Revealing the mechanism and influential path of emitter clogging in drip irrigation is the basis to control this issue. Eight commonly used flat emitters were tested to analyze the effects of emitter flow path geometric parameters on the hydraulic indexes, clogging performance, and composition of clogging substances, and the influential path was established through the path analysis method. The results indicated that the average cross-sectional velocity (v) was significantly correlated to clogging degrees and clogging substance formation. v directly affected the formation of clogging substance components, and was influenced by the width–depth ratio (W/D) and the relative radius (A1/2/L). Among all the components of the clogging substances, solid particle (SP), and CaCO3 and MgCO3 precipitates (C–MP) directly affected emitter clogging process, while phospholipid fatty acids (PLFAs) and extracellular polymeric substance (EPS) mainly relied on the indirect impacts. Therefore, emitter with larger v rather than that with larger Q should be a better choice from the perspective of the anti-clogging performance, and larger v could be obtained through the optimized design of emitter structure by controlling the appropriate ranges of W/D and A1/2/L.

Composite clogging characteristics of emitters in drip irrigation systems

This study investigated the characteristics of emitter clogging substance in 16 kinds of drip irrigation emitters using 3 kinds of water sources that could typically induce composite clogging in the Yellow River irrigation area. The research results indicate that there was remarkable randomness in the behavior of composite clogging substances in a single emitter, and peak randomness ( $$\Delta F_{Q}^{t}$$ ) values were 19.5–20.8%, 20.5–22.4% and 25.9–28.2% higher than that with physical, chemical and biological clogging, respectively. Clogging in a single emitter also exhibited recoverability ( $$R_{Q}^{{{\text{CD}}}}$$ ) which would be lost when the clogging degree reached 60–75%, and recoverability ( $$R_{Q}^{{{\text{CD}}}}$$ ) showed the opposite variation rule to randomness ( $$\Delta F_{Q}^{t}$$ ). Though clogging in a single emitter was associated with certain randomness and recoverability, the overall variation of the micro-irrigation system's average discharge variation ratio (Dra) and Christiansen’s uniformity (CU) was not affected. Instead, the two showed relatively consistent dynamic variation of mild fluctuation followed by acute descending. The fluctuation trend during the earlier stage lasted from 128 to 660 h, and descending branch slopes of Dra and CU during the later stage were 0.09–0.12 and 0.13–0.21, respectively. In terms of various types of emitters, $$\Delta F_{Q}^{t}$$ generally demonstrated dynamic variation for a tape emitter (highest), a single-side labyrinth emitter (slightly lower), a cylindrical emitter (even lower) and a flat emitter (lowest). However, the dynamic variation of $$R_{Q}^{{{\text{CD}}}}$$ , Dra and CU were inverse. As far as various water sources were concerned, mixing water had the highest $$\Delta F_{Q}^{t}$$ , followed by Yellow River water, and surface lake water had the lowest $$\Delta F_{Q}^{t}$$ , while variation characteristics of $$R_{Q}^{{{\text{CD}}}}$$ , Dra and CU among the three water sources were inverse. The present study could provide reference for revealing the characteristics of composite clogging in emitters, thus constructing effective clogging control methods.