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Impact of hydrodynamics on clay particle deposition and biofilm development in a labyrinth-channel dripper

Ait-Mouheb, Nassim, Schillings, Juliette, Al-Muhammad, Jafar, Bendoula, Ryad, Tomas, Séverine, Amielh, Muriel, Anselmet, Fabien
Irrigation science 2019 v.37 no.1 pp. 1-10
bentonite, biofilm, chemical oxygen demand, clay, emitters (equipment), fouling, hydrodynamics, kaolin, kinetic energy, microirrigation, nutrient solutions, sodium chloride, topology
To better understand the physical and biological clogging in drip-irrigation, a study was conducted on the impacts of hydrodynamic conditions on clay particle deposition and biofilm development in drippers using an optical method. A transparent milli-fluidic system composed of labyrinth channels was used to identify areas most susceptible to particle clogging using two different types of clay suspensions: sodium bentonite and kaolin. The impact of salt addition [(NaCl) = 200 mg L⁻ ¹] on the clay deposition was also analyzed. Biofilm development was studied using the same methodology using a nutritive solution (chemical oxygen demand, COD = 200 mg L⁻¹). In addition, fluid dynamics simulations were performed along the labyrinth channel to understand the effect of flow behaviour on the fouling. Computational fluid dynamics results show two types of flow topology: high velocity in the main flow (around 1 m s⁻ ¹) and low velocity in the vortex zones (less than 0.2 m s⁻ ¹) found in the channel corners. Using an optical method, kaolin deposition and biofilm growth in the dripper were observed to occur mainly in the inlet channel and initial vortex zones, which are characterized by lower mean velocity and turbulent kinetic energy values. This part of the dripper can be considered as a bottleneck that amplifies the fouling phenomena and which should be optimized. With the addition of NaCl, kaolin particles tend to form bigger flocs. Therefore, more significant particle deposition is observed, but this is not the case of bentonite for which no fouling is observed along the dripper.