Control of the residual aluminum in drinking water by optimization of the coagulation process

Coagulation-Flocculation is an unavoidable stage in water treatment. It permits to reduce the color and the turbidity, normally caused by the organic and inorganic contaminants to acceptable levels for drinking water or for wastewater. The used coagulants can be organic or inorganic nature. The main goal of this work is to make the follow-up of water quality parameters and the optimization of the clarification stages in the drinking waters treatment station, by determination of the break point in the stage of the prechloration and optimization of the coagulant (aluminum sulphate) proportion. The determination of the anions concentration by means of the ionic chromatography before and after coagulation-flocculation shows that the stability and the solubility of the aluminum species are strongly affected by the presence of these anions. Consequently, the content of the anions affects the process of coagulation and must be taken into account in the optimization of this process. We present in this communication, the results of the pH, concentration of the coagulant, time of coagulation effect on the coagulation process .These factors show optimum values. The research of residual aluminum in the two water studied during this work shows that the aluminum content is lower than 200 g/L at the pH optimum.