Clogging of drippers caused by suspensions of kaolinite and montmorillonite clays

Clay particles under certain physico-chemical and hydrodynamic conditions can form agglomerates after passing through a filtering system, which favours clogging of the emitters. The main factors interfering with the aggregation potential of clay particles are the type of clay mineral, pH, and ionic strength of the irrigation water. This study analysed the influence of ionic strength and type of clay mineral on clogging, discharge variation, and particle deposition in turbulent-flow non-pressure compensating drippers. Two types of clay (kaolinite and montmorillonite) at a concentration of 500 mg L-1 and four values of ionic strength (0.31, 0.81, 0.02, and 0.01 mol L-1) promoted by the addition of different salts to the solution were used. Clogging tests were conducted with two commercial models of drippers (0.6 and 1.7 L h(-1)). The deposition zones along the labyrinth channel were analysed using a transparent milli-fluidic system coupled to an optical microscope. Deposition of particles inside dripper labyrinths was observed and this process was strongly influenced by the nature of the clay. The regions of highest particle deposition were vortices zones located in the first baffles of the labyrinths. Kaolinite particles had greater potential of accumulation in the labyrinths than montmorillonite particles. There were fluctuations in the drippers' discharge during the clogging experiments, but the discharge variations observed were not sufficient to classify the emitters as clogged in any of the test conditions. Clay, as an isolated agent, did not cause full clogging in the emitters evaluated under any of the ionic strength conditions studied. Since particles did not accumulate in the region of the main flow, we suggest that clay particles alone have no potential to cause full clogging of drippers, but may contribute to clogging build-up.