Relations between rainfall, water quality of the natural water and water treatment - case study

Abstract

The interrelationships among the rainfalls, the water quality of the Gavião Reservoir (in the municipality of Pacatuba/CE), and the water treatment carried out in its downstream station have been analyzed. Variables such as apparent color, turbidity, and raw water pH as well as the dosages of chemical products used in the station have been followed. The pH in the first semester (rainy season) had a pH average of 7.53 + 0.3 and 7.69 + 0.1 in the second semester (dry season). Turbidity had an average of 8.85 + 2.6 uT in the first semester, and 9.91 + 2.2 uT in the second semester. Yet, the color variable average in the first semester was 40.9 + 2.8 uH, and 38.9 + 2.8 uH in the dry season. Concerning the dosages of chemical products, it has been found out that Chlorine Gas was higher in the rainy season (10.28 + 0.6 mg/L) than in the dry season (9.63 + 0.2 mg/L). Yet, the ACP dosages have varied a little (rainy season: 7.06 + 0.5 mg / L, dry season: 6.18 + 0.6 mg / L). The doses of Cationic Polymer have followed the changes in water quality (first semester: 2.21 + 0.3 mg/L, second semester: 1.55 + 0.3 mg/L). It is understood that rainfalls have influenced the pH and turbidity behavior by reducing them. Yet, the color has increased during the rainy season. Regarding the chemical products, only the ACP has not changed much. All the others have had their dosages increased in the rainy season.