Efect of type of emitter self‑cleaning mechanism and its structure on the performance of drip irrigation system using efuent of rainbow trout fish

Abstract

The anti-clogging ability of the emitters depends on their automatic self-cleaning mechanism, the structure and geometry of the fow path, and the type of material carried by irrigation water. Suspended solids in fsh farm efuents 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 fushing mechanisms of emitter were evaluated. The three emitter fushing mechanisms were: (1) continuous self-cleaning with silicone diaphragm, (2) on-of self-cleaning with silicone diaphragm, and (3) continuous selfcleaning with silicone rubber path. Four drip irrigation units for irrigation with fresh water (control) and efuent of a rainbow trout fsh farm were designed and implemented. Two of these units were for control treatment (with and without fltration system) and the other two for efuent treatment (with and without fltration system). A total of 270 pressure compensating emitters of Microfapper, 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 Coefcient (CU) and Season Relative Discharge Coefcient of Variation (CV (Dra) S) were used. During the irrigation season, the changes in Dra and CU fuctuated, especially for the Microfapper emitter. The maximum percentage of completely clogged emitters was 83.3% and the lowest Dra was 14% with Microfapper emitters using not fltered efuent. The Dra for these emitters with efuent treatments under no fltration decreased signifcantly (p <0.05) compared to control treatment. Without fltration, the type of water, irrigation periods, emitter type and discharge and their interaction afected the relative discharge signifcantly (p<0.05). No completely clogged emitter was found under fltration conditions. For both control and efuent treatments, fltration signifcantly (p<0.05) increased Dra of 4 and 8 l h−1 Microfapper and 8 l h−1Netafim emitters. Efuent fltration improved Dra of Microfapper emitters by an average of 41%. The 4 l h−1 Netafim emitter performed best in all conditions independently of irrigation water and fltration system, without signifcant (p<0.05) diferences between them. Overall, the performance of Netafim and Corona emitters was similar and better than Microfapper, 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 signifcant diference in some cases)