Characterization of scale deposits formed in sanitary hot water pipelines in the northern tourist zone of Agadir city

Abstract

The formation of scale on surfaces in contact with water is due to many reasons as the hardness of water and its temperature. Therefore, this phenomenon of scale in water pipelines is a common and inevitable problem in the regions that exploit or use groundwater with high rigidity. The circuits fed by hot water are easily reached by hard water scaling. The deposition of encrusting curst at the level of walls in touch with water is due to many technical, economic and environmental problems. It causes a reduction in water flow and a decrease in the efficiency of heating systems.

In this study, we are particularly interested in studying the phenomenon of hard water scaling caused by sanitary hot water in a tourist unit situated in the north of the seaside in the city of Agadir. First, we have evaluated the physico-chemical quality of water in use in this tourist unit. Secondly, we conducted a qualitative and quantitative analysis of the scale found in the circuits that transport sanitary hot water. Several analytical techniques were used to reach this goal namely: X-ray fluorescence (XRF) which shows that 85.50% of scale is represented by Calcium Carbonate. Whereas infrared spectrometry (IR) demonstrates the existence of the Carbonate anion CO₃^2-. In addition, due to thermogravimetric analysis (TGA) and differential thermal analysis (DTA) we found that the endothermic event shows the decomposition of Calcium Carbonate of CaO and CO₂ in the temperature range of 660 C° to 820 C°. For scanning electron microscopy (SEM), it indicates that the scale takes the form of needle-like aragonite crystals. At last, the X-ray diffraction (XRD) shows that the scale is composed essentially of Calcium Carbonate of the type aragonite.

The results of the different techniques of characterisation are in concordance in the scaling of the circuits of sanitary hot water in the tourist unit under study.