Competitiveness of removing heavy metals in industrial effluent by using hydroxide precipitation versus sulphide precipitation

Rapid industrialization activities in the country contributed to pollution included the electroplating industry activities which is the effluent wastewater contained high concentration of heavy metals that poses potential health risks to the public. Pollution of heavy metals in water body may cause serious health effects to the human such as cancer, organ damage and also death, in extreme cases. This problem lead to unpredictable impact to the environment, public health, and economic direct or indirectly. This experiment was conducted to determine the efficiency of removal heavy metals which are copper (Cu), zinc (Zn), aluminium (Al), nickel (Ni) and chromium trivalent (Cr III) by using hydroxide precipitation and sulphide precipitation. The pH selection and coagulant dosage play important role to enhance the removal of heavy metals. The optimum pH and coagulant dosage were determined via a jar test for both types of samples. The coagulant used in the experiment were ferric chloride (FeCl3) and poly aluminium chloride (PAC) as coagulant booster to enhance the process. Jar test was conducted on two different type of chemical precipitation which is hydroxide precipitation by using sodium hydroxide (NaOH) and sulphide precipitation by using sodium sulfide (Na2S). In order to remove chromium trivalent, sodium metabisulfite was used to reduce chromium hexavalent to chromium trivalent. The findings in this study shows that sulphide precipitation removed heavy metals more efficient compare to hydroxide precipitation based on the removal of turbidity. Besides the removal of heavy metals, the total suspended solid (TSS) and chemical oxygen demand (COD) also shows a decrease after the precipitation treatment. Thus, this study can be used to treat industrial effluent that contained heavy metals.