Understanding and controlling chemical clogging in drip irrigation: Integrating experimental methods, density functional theory calculations and molecular dynamics simulations

Abstract

The chemical clogging of water drips is the main obstacle to the adoption and spread of microirrigation technology. The aim of this research is to understand the scaling phenomenon by identifying the substances responsible for emitter clogging using a combination of different methods of characterization and to investigate the effectiveness of a new product ‘Melacide P/2’ as a calcium carbonate scale inhibitor. A non-electrochemical method from the Laboratory of Chemistry and Genie of the Environment (LCGE) was employed to investigate the effect of the inhibitor against calcium carbonate precipitation at 25°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the effect of Melacide P/2 on the scale morphology and crystalline phases. Density functional theory (DFT) and Monte Carlo (MC) simulations were performed to support the experimental results. Characterization techniques revealed that the scale recovered from the drips consisted mainly of calcium carbonate, a variety of calcite. The experimental data indicate the likelihood of preventing calcium carbonate precipitation after the addition of a very small amount (0.30 mg L⁻¹) of Melacide P/2 under the conditions of the experiment. XRD and SEM revealed that the inhibitor tested has the potential to disrupt or block regular CaCO₃ crystal growth and transform a more stable and adherent scale of calcite to aragonite, which is easy to eliminate. The theoretical approach adopted supports the experimental findings. Therefore, Melacide P/2 could be used as a cost-effective green-scale inhibitor to protect microirrigation systems from unwanted scale formation.