Abstract
Mineral processing requires large amounts of water, but, often in the remote locations of many mines, sufficient fresh water frequently cannot be supplied. Therefore, recycling of water is important in mineral processing and enhancing the efficiency of the liquid-solid separation and dewatering steps in mineral processing wastewater treatment is critical. The objectives of the study were to evaluate the effect of anionic flocculant dosage and sludge recycling (SR) on solid removal and sludge dewaterability. Different combinations of the flocculant dosage with and without SR were applied in a mineral-processing wastewater treatment pilot plant. Increasing the amount of flocculant dose of 1.1% v/v (flocculant solution to wastewater) did not significantly decrease the turbidity of the treated water, while the combination of a flocculant with SR increased the zeta potential. Increasing flocculant dose adversely affected dewaterability, although the dewaterability of the 0.6% v/v flocculant-treated sludge significantly increased after aging of the sludge. Sludge recycling was effective for increasing the dewaterability, and a flocculant dose of 1.1% v/v with SR led to formation of large flocs that were stable during aging and sonication.
Highlights
Mineral processing separates valuable minerals from ores, and includes the use and transport of water throughout the treatment stages
Sludge recycling to the flocculation process is beneficial for solid settling and subsequent dewatering in part due to using residual coagulation and flocculation chemicals in the sludge [7]
There are no standards for wastewater recycled after mineral processing
Summary
Mineral processing separates valuable minerals from ores, and includes the use and transport of water throughout the treatment stages. A common and valuable process for mineral separation, is conducted with water containing 25–35 wt % solids and consumes 1.9–3.0 m3 of water per ton of ore processed [1]. Mineral-processing wastewater includes pollutants such as solid particles, heavy metals, and residual chemical reagents [2]. Coagulation-flocculation process is regarded as one of the most important and widely used treatment processes of industrial wastewater [3] and raw water [4] due to its simplicity and effectiveness. Because mineral-processing wastewater contains suspended solids, coagulation and flocculation are important steps in treating the water. The coagulation and flocculation processes work to remove suspended solids, and enhance the removal of heavy metals in treated water [6]. It is known to enhance the efficiency of turbidity reduction in low-turbidity raw water [8]
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