Influence of suspended solid particles on calcium carbonate fouling in dripper labyrinths

Calcium carbonate (CaCO₃) fouling process in dripper prototypes was studied in the absence and presence of suspended solid particles (SSP) at concentrations of 125 and 500 mg L⁻¹. Eleven flat and non-pressure-compensating dripper prototypes were evaluated. Five prototypes (Model A) present flow with well-developed vortices, whereas the other six prototypes (Model B) present more uniform flow with undeveloped vortices. Water with hardness of 200 and 300 mg L⁻¹ as CaCO₃ was used in the experiments. The dripper prototypes operated for 200 h, and the discharge variation rate (Dra) was determined every 40 h. Images of the interior of the labyrinths were acquired to investigate the fouling patterns. The mass of material fouling the labyrinth of the prototypes was determined and correlated to the geometric parameters of the labyrinths. The deposited material was analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SSP directly influenced the CaCO₃ fouling processes. In the absence of SSP, heterogeneous nucleation was dominant in the prototype walls and occurred uniformly throughout the labyrinth, interfering directly in the Dra of the model B prototypes. The model A prototypes were more resistant to clogging and did not clog during the experiments. Once added to the water, the SSP functioned as an effective competitor of CaCO₃ nucleation and growth sites; thus, heterogeneous nucleation started occurring preferably on the SSP surface, reducing the fouling in the labyrinth walls. The prototypes that clogged in the tests in the absence of SSP were resistant to clogging in the SSP concentration of 500 mg L⁻¹. The presence of SSP changed the crystal habit of CaCO₃, and it precipitated in the form of calcite. The nucleation of CaCO₃ directly on the SSP surface is interesting from the point of view of clogging processes, and drippers with better sediment transport capacity are beneficial.