Coagulation and flocculation are essential processes in a number of diverse disciplines, including biochemistry, cheese manufacturing, rubber manufacturing, and in water and waste water treatment. Coagulation-flocculation is effective for removing high concentration organic pollutants and heavy metals in water and wastewater. However, limited information exists on the efficiency of this coagulation-flocculation process for biodiesel wastewater treatment. The biodiesel wastewater is basic (alkaline), with a high content of oil and grease, and a low content of nitrogen and phosphorus. As such, biological treatment of the biodiesel wastewater is expected to be very difficult. For this reason supportive physic-chemical methods are often used. Although one of the most frequently employed method is coagulation. Therefore, this study was conducted to investigate the efficiency of coagulation and flocculation processes for removing suspended solid (SS), color, COD and oil and grease from biodiesel wastewater. Aluminum sulfate, polyaluminum chloride, ferric chloride and ferric sulfate as a coagulant in biodiesel wastewater treatment were studied using a standard jar test apparatus. The result shows that, at the optimum dose of PAC (300 mg/L), the percentage removal of SS, color, COD and oil and grease respectively 97%, 95%, 75% and 97% compared to only 92%, 92%, 53% and 99% at the optimal dose alum (500mg/L), 95%, 93%, 63% and 97% at the optimum dose of ferric chloride (350 mg/L) and 88%, 88%, 54% and 94% at the optimum dose of ferric sulfate (450 mg/L). The effect of coagulant dosages on suspended solid (SS), color, COD and oil and grease removal showed similar trend and PAC was found to be superior was observed at reasonable lower amount of coagulant i.e. 300 mg/L. The results showed that coagulation-flocculation is effective as a pre-treatment for treating biodiesel wastewater.

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The suitability of micro peat (MP) and activated carbon (AC) mixed media as a composite adsorbent for the landfill leachate treatment in terms of COD reduction and color removal was investigated in this study. All the adsorption media was pulverized and sieved to a particle size of 150 μm. The MP-AC composite media efficiently removed 87% COD at optimal ratio 1.5:2.5 and 74% color at optimal ratio 2.0:2.0, within 120 min of contact time, 200 rpm of shaking speed at pH 7. The findings revealed that Langmuir isotherm best described the uptake of COD and color which implies that the adsorption of leachate in this study onto MP-AC composite media was homogeneous on a mono layer surface. The kinetic data and the factor controlling adsorption process fitted better to the pseudo-second-order model. Energy of adsorption (E) were observed as 267.26 kJ mol-1 and 79.06 kJ mol-1 for COD and color respectively indicating chemisorption as the limiting controlling step for the reduction of COD and color onto MP-AC composite media. The overall rate of the COD and color adsorption processes onto MP-AC composite media appears to be dominated by chemisorption. The pattern of adsorption showed that micro peat offers a cost effective alternative and can be utilized as partial replacement of conventional media (AC) for the removal of organic matters from landfill leachate.

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