Lin Zhang

BACKGROUND: Although reclaimed wastewater drip irrigation (RWDI) is an effective technology for alleviating agricultural crop water stress and protecting the environment, the reclaimed wastewater (RW) may cause emitter clogging. Discharge ratio variation (Dra) and coefficient of uniformity (CU) play a key role in exploring the clogging degree of the emitter. Therefore, a meta‐analysis was conducted to identify optimal management methods with an acceptable Dra and CU under RWDI.RESULTS: The results indicate that the higher the concentration of various substances in RW, the higher is the risk of the emitter clogging. Suitable concentrations of iron (Fe), manganese (Mn), total suspended solids (TSS), chemical oxygen demand (COD), water hardness and calcium ions (Ca²⁺) in RW were determined to be 0–0.2, 0–0.02, 0–50, 20–30, 200–250 and 0–40 mg L⁻¹, respectively. Pressure‐compensating emitters with relatively high discharge (>2 L h⁻¹) could prevent clogging in RWDI systems.CONCLUSION: Based on the data analysis, a cumulative RWDI operation time of 375 h was determined as the most suitable time for lateral flushing to prevent clogging. This study identifies the conditions under which an increase in the service life of RWDI systems can be achieved. © 2022 Society of Chemical Industry.

Pulsating pressure plays an important role in improving the poor irrigation quality and the uneven water distribution caused by the terrain slope. Water distribution is one of the key factors in design of the sprinkler irrigation system, however, it is difficult to measure in practice. To provide appropriate technical parameters for the design of sprinkler irrigation system with pulsating pressure on sloping land, a mathematical model was established according to the water conservation principle and finite element idea, and its accuracy was experimentally verified. The model was applied to study the effects of terrain slope, sprinkler arrangement, sprinkler spacing and average pulsating pressure on water distribution on sloping land. The results showed that the water distribution was more favorable under the gentle terrain slope, when slope decreased from 25% to 5%, the uniformity increased from 74.47% to 86.22%. Sprinklers arranged in equilateral triangle and with the spacing close to R0 had the best water distribution uniformity, the uniformity coefficient (CU) of which was 11.43% and 8.75% higher than that in square and rectangular arrangement, respectively. The CU increased with the increase of the average pulsating pressure. However, the effect of increasing water pressure on promoting the uniformity of water distribution gradually decreases. Therefore, when using the Rainbird R5000 sprinkler on sloping land with pulsating pressure, it is suggested that the sprinkler irrigation systems should be arranged below the terrain slope of 20%, and operated at the average pulsating pressure of 300 kPa. The suitable sprinkler arrangement is the equilateral triangle, and with the spacing of 0.8R0 to 1.0R0. Keywords: sprinkler irrigation, water distribution on sloping land, estimation model, pulsating pressure DOI: 10.25165/j.ijabe.20221502.6662 Citation: Fu B Y, Huang Y, Zhang L. Estimating water distribution of the rotating sprinkler with pulsating pressure on sloping land. Int J Agric & Biol Eng, 2022; 15(2): 39–47.

Infiltration irrigation with saline water is a more effective method than drip irrigation to alleviate water scarcity worldwide, but so far, no report has discussed the clogging rules of ceramic emitters, a major component of infiltration irrigation system. To explore the clogging mechanism of ceramic emitter in saline water infiltration irrigation system, we used four kinds of saline water sources with electrical conductivity (EC) of 0.18, 1.74, 3.78, and 7.74 ds/m, respectively. In addition, we specifically investigated the law of discharge ratio variation (Dra) of ceramic emitters, as well as the composition and growth process of clogging substance. The results indicated that the Dra of ceramic emitters decreased in the process of saline water irrigation, and the higher the EC, the more obvious the decrease. The calcium carbonate (CaCO₃) was the main component of the clogging substance in the inner wall of ceramic emitters. The clogging part was a layer on the inner wall of the emitters rather than the pores in the walls, and the clogging did not occur suddenly. Instead, it was caused by the long–term accumulation of the clogging substance. Moreover, with the increase of EC, the flocculation between the clogging particles in the water was enhanced and thus promoted the formation of stable and compact aggregates, which fundamentally led to the clogging acceleration of ceramic emitters. This clogging mechanism of ceramic emitters can provide some theoretical reference for the establishment of anti-clogging strategy.

The instability of diafiltration is a widespread problem in the practical application of microporous ceramic filtration membranes. In this paper, a series of microporous ceramic filter membranes were prepared using inexpensive standard sand and river sand as matrix materials. Semi-empirical formula for the effective permeability radius of ceramic membranes with respect to time was established from analysis of the response mechanism between water flow and material properties. Finally, on the basis of theoretical analysis, some measures were proposed to improve permeate flux. The experimental results showed that during the initial stage of filtration, the microporous ceramic filter membrane had a large change in permeate flux, and during the late stage of filtration, permeate flux tended to be stable. Over time, open porosity and closed porosity changed the actual seepage area of the ceramic membrane, and this affected the stability of permeate flux and final stable permeate flux. The roughness of the inner wall of microporous ceramic pores affected the hydraulic loss coefficient, and this controlled the outflow process. Trace elements that were rich in sand produced a large amount of glass phase after sintering. The glass phase was rich in polar groups and formed a temporary hydrogen bond with the small flow of water molecules. It led to an increase in viscous resistance effect of the side wall along the water flow and the extent of the permeate flux of the ceramic membrane changed with time.

Choosing reasonable design parameters for ceramic emitters used in subsurface irrigation is important for reducing the deep percolation of water and improving the water use efficiency. Laboratory experiments and numerical simulations with the HYDRUS-2D software were carried out to analyze the effect of soil texture on the infiltration characteristics of porous ceramic emitters used for subsurface irrigation. HYDRUS-2D predictions of emitter discharge in soil and wetting front are in agreement with experimental results, and the HYDRUS-2D model can be used to accurately simulate soil water movement during subsurface irrigation with ceramic emitters in different soil textures. Results show that soil texture has a significant effect on emitter discharge, soil matrix potential around the emitter, and wetting front. For 12 different soil textures, the aspect ratio of the wetting front is basically between 0.84–1.49. In sandy soil, the wetting front mainly appears as an ellipse; but in the clay, the wetting front is closer to a circle. As irrigation time increases, emitter discharge gradually decreases to a stable value; however, emitter discharge in different texture soils is quite different. In order to improve the crop water use efficiency in sandy soil, soil water retention can be improved by adding a clay interlayer or adding water retention agent, reducing the risk of deep percolation and improving the water use efficiency.

Sprinkler irrigation application uniformity is an important indicator for sprinkler irrigation system design, which can be expressed by the Christiansen uniformity coefficient (CU). The calculated accuracy of CU is closely related with catch‐can spacing and grid size. In theory, the smaller the catch‐can spacing and grid size are, the more accurate the calculation of CU is. However, smaller catch‐can spacing needs more labor in water distribution measurement, and smaller grid size needs more computer runtime to calculate CU. In order to recommend the proper catch‐can spacing and grid size, an experiment is carried out to obtain four different water distribution patterns, and data characteristics for water distribution with various catch‐can spacing and the effect of catch‐can spacing and grid size on CU are studied in the paper. The results show that CU is overestimated for the larger catch‐can spacing, especially when the distribution of water for the pattern is non‐uniformity. CU changes very little within a certain catch‐can spacing and grid size for all the four patterns. Considering the accuracy of CU calculation, labor cost, and the computational runtime, the recommended catch‐can spacing is 1.96 m for pattern I, 0.92 m for patterns III and IV, and the recommended grid size in the calculation of CU is 1.25, 1.0, and 0.5 m for patterns I, III, and IV, respectively.