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Abstract
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The anti-clogging ability of the emitters depends on their automatic self -cleaning mechanism, the structure and geometry of the flow path, and the type of material carried by irrigation water. Suspended solids in fish farm effluents are mostly organic with a low volumetric mass and high compressibility. In the present study, three types of pressure-compensating emitters, two discharges with three flushing mechanisms of emitter were evaluated. The three emitter flushing mechanisms were: 1) continuous self-cleaning with silicone diaphragm, 2) on-off self-cleaning with silicone diaphragm, and 3) continuous self-cleaning with silicone rubber path. Four drip irrigation units for irrigation with fresh water (control) and effluent of a rainbow trout fish farm were designed and implemented. Two of these units were for control treatment (with and without filtration system) and the other two for effluent treatment (with and without filtration system). A total of 270 pressure compensating emitters of Microflapper, Netafim and Corona brands with discharge of 4 and 8 l h-1 through 24 irrigation events lasting 192 operating hours were evaluated over a period of 10 weeks. The indices of Relative Discharge (Dra), the Christiansen Uniformity Coefficient (CU) and Season Relative Discharge Coefficient of Variation (CV (Dra) S) were used. During the irrigation season, the changes in Dra and CU fluctuated, especially for the Microflapper emitter. The maximum percentage of completely clogged emitters was 83.3% and the lowest Dra was 14% with Microflapper emitters using not filtered effluent. The Dra for these emitters with effluent treatments under no filtration decreased significantly (p<0.05) compared to control treatment. Without filtration, the type of water, irrigation periods, emitter type and discharge and their interaction affected the relative discharge significantly (p<0.05). No emitters completely clogged were found under filtration conditions. For both control and effluent treatments, filtration significantly (p<0.05) increased Dra of 4 and 8 l h-1 Microflapper and 8 l h-1Netafim emitters. Effluent filtration improved Dra of Microflapper emitters by an average of 41%. The 4 l h-1 Netafim emitter performed best in all conditions independently of irrigation water and filtration system, without significant (p<0.05) differences between them. Overall, the performance of Netafim and Corona emitters was similar and better than Microflapper, which showed the independence of the relative discharge of the emitter to the type of self-cleaning mechanism and its dependence on the type of structure from its self-cleaning mechanism. For each brand, the performance of the emitters with lower discharge (4 l h-1) was better than the higher discharge (with significant difference in some cases).
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