Effect of the Rapid Mixing Speed on the Coagulation-Flocculation Process Using Natural-Based Coagulant in Domestic Wastewater Treatment

Abstract

Natural coagulants are an imperative alternative method as they offer a sustainable and eco-friendly approach to replace chemical coagulants in domestic wastewater treatment. The objectives of this research are to investigate the effect of rapid mixing speed on the removal performance of turbidity, total suspended solids (TSS) and total dissolved solid (TDS) using banana peel waste as natural coagulant in domestic wastewater using coagulation-flocculation process. The banana peels were converted into fine powder and used at fixed dosage of 0.02 g/L. The parameter of rapid mixing speed was varied at three different speeds of 100, 150 and 200 rpm for duration of 3 minutes, followed by slow mixing speed at 10 rpm for 20 minutes and settling time period of 30 minutes. The findings indicated that the turbidity removal increased slightly with an increase of rapid mixing speed, with the highest removal of 88.21%. For TSS, the removal performance showed 87.53% at 100 rpm and decreased with the increase of speed, indicating floc breakage due to the high-speed mixing, thus reducing the settling efficiency. While TDS removal was observed, the best result was rapid mixing speed at 150 rpm (23.37%), suggesting limited impact of the speed on the dissolved solids. The result demonstrates the factor of rapid mixing speed enables initial dispersion and particle destabilization, excessive agitation can compromise floc stability, mainly for suspended solids. Hence, it is crucial to optimize the rapid mixing intensity to enhance the coagulation-flocculation performance of the banana peels as natural coagulants, to ensure the treatment of domestic wastewater becomes more effective and sustainable.