Effect of temperature on turbidity removal by coagulation: Sludge recirculation for rapid settling

Temperature plays a critical role in turbidity removal by coagulation-a widely used method for removing suspended charged particles. This study, therefore, examines the effect of temperature on turbidity removal through the coagulation process. Streaming potential (SP) was measured during the experiment at different temperatures in combination with other parameters such as pH, hydraulic conditions, and sludge recirculation, and coagulation-flocculation efficiencies were evaluated in terms of turbidity removal. Results show lower SP at lower pH (pH < 7) and lower temperature (<20 degrees C) conditions whereas higher SP at higher pH and higher temperatures. Thus, the adequate coagulant doses to neutralise the charged particles are proportional to the pH and temperature. Results also exhibit that the turbidity removal efficiency is significantly affected by temperature. Turbidity removal efficiency (after 10 min of sedimentation time at pH 7) was calculated to be 83% at 2 degrees C, and reduced to 78% at 40 degrees C. That is also affected by the solubility of the inorganic coagulant used. Sludge recirculation was observed to be an effective method of improving turbidity reduction under all the conditions investigated, and the amount of reuse sludge was found to be temperature dependent.

Automated summary

Temperature plays a critical role in turbidity removal by coagulation. The appropriate coagulant dosage is proportional to pH and temperature. Temperature significantly affects turbidity removal efficiency, which is also influenced by coagulant solubility and sludge recirculation.