Zeitschrift für Chemieingenieurwesen und Prozesstechnologie
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Recovery of Calcium Carbonate from Wastewater Treatment Sludge Using a Flotation Technique

Jannie P. Maree, Caliphs M. Zvinowanda, Munyaradzi Mujuru, Regina M. Matsapola, David J. Delport and Wynand J. Louw

The use of flotation technique for the recovery of calcium carbonate (CaCO3) from wastewater treatment sludge was investigated in this study. The parameters that were investigated included dosage of floating agents (sodium oleate and sunlight dish liquid) and the percentage solids of the slurry. The experiments were performed by floating sieved and un-sieved materials and CaCO₃ was determined for both conditions as well as from tailings.

Initial CaCO₃ analysis for the bulk material indicated that sieved and un-sieved materials had 63.4% and 32.9% CaCO₃ content by weight respectively. The modification of pH was effected by dosing 1g NaCO₃ to both 1000 g of sieved and un-sieved materials which was sufficient to raise the pH of the slurry to 9.5. A lower average recovery of 2.33% was observed on un-sieved material after using sodium oleate as a collector when compared to sunlight liquid of 31.6%. Therefore, it was concluded that for un-sieved material sunlight dishwashing liquid was a better collector compared to the latter. The results of this study proved that there is great potential of recovering commercial grade limestone from wastewater sludge.