Critical controlling threshold of internal water shear force of anti-clogging drip irrigation emitters using reclaimed water

Improving the anti-clogging ability of drip irrigation emitters is the most direct and effective way to relieve the clogging issue. Different from the traditional main channel optimization method, washing the internal wall of the flow path utilizing the fully developed local vortices successfully enhanced the self-cleaning ability of drip irrigation emitters. Under this condition, appropriate internal water shear force is important for vortices’ development and anti-clogging optimization of emitter flow path. However, no related results were reported yet. Based on these, a controllable indoor experiment was carried out to systematically study the impacts of internal water shear forces on the clogging substances’ growth and explore the appropriate range of water shear forces. The results indicated that the clogging substance components using three types of reclaimed water (including solid particles (SP), phospholipid fatty acids (PLFAs) and extracellular polymeric substances (EPS)), showed quadratic patterns with internal water shear forces (R2 > 0.89, p < 0.01), and the maximum contents were observed when τ was 0.2 Pa or 0.4 Pa. As the functions and proportions differed for each component, the appropriate ranges for SP, PLFAs and EPS increment varied obviously. After a comprehensive consideration of the dynamic response of clogging substances to τ, the critical controlling threshold of internal water shear force was obtained as (0, 0.26 Pa) ∪ (0.46 Pa, 0.70 Pa), based on the conjunct range of all three components. The results acquired in this paper could provide theoretical references to anti-clogging optimization of drip irrigation emitter products.