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High amounts of black liquor are generated from bioethanol production by using oil palm empty fruit bunches. The black liquor is waste from alkaline pretreatment, it contains high amount of an alkaline solution (NaOH). The black liquor wastewater was highly contaminated with organic materials, and quite toxic for aquatic ecosystems if discharged directly into waters. This study aimed to determine ability of Fenton process combined with coagulation to treat black liquor. The addition 5% of polyaluminium chloride (PAC) could decolorized black liquor, degraded lignin, and produced sludge 70.64%, 68.28%, and 2.76 gram, respectively. Decolorization of black liquor was in line with degradation of black liquor because lignin is the main compound in black liquor. SEM images after addition of PAC of 5% indicated fragmentation of structure. Fenton reagent consist of 0.7 M FeSO4+ 3M H2O2 has able to decolorize black liquor, degrade lignin, and produce sludge 51.67% and 25.44%, and 0.44 gram, respectively. It was concluded that black liquor wastewater from bioethanol can be treated by using Fenton process combined with coagulation. However, these methods still need improvement to obtain the higher degradation rate, and coagulation sludge needs further consideration. [ABSTRACT FROM AUTHOR]

Black liquor is one of the main by-products of the pretreatment process in bioethanol production from oil palm empty fruit bunches. Black liquor wastewater releases black coloured effluent with high chemical oxygen demand (COD) and low dissolved oxygen (DO). It had a distinctive dark coloration, high alkalinity (pH=13), high organic content (COD > 50,000 ppm) and a high solid content (TSS > 5,000 ppm). Lignin destruction can be done by using high oxidation from OH radical system such as advanced oxidation processes (AOPs). Thereafter, the high concentration of COD, color, and TSS can be removed. The general aim of the present investigation was to determine degradation of black liquor wastewater by using a combined coagulation and Fenton-like methods. In this research, we use Poly Aluminum Chloride (PAC) as a coagulant and FeCl3.6H2O and H2O2 for Fenton-like's reagent. The process was conducted in jar test at 200 rpm for 30 minutes and after that slowly mixed for 2 hours and left for sedimentation 24 hours. 50 ml black liquor was added with variation dose of 1-5% PAC, and 10 % Fenton-like reagent. Hydroxyl radical was generated by the Fentonlike's reagent (ratio FeCl3.6H2O: H2O2 was varied). The highest decolorization of black liquor 70 % was obtained under 5% PAC coagulant. The pH of the wastewater was reduced from 13.00 to 8.07 after the addition of the coagulant. The decolorization of original black liquor was approximately 58% through the Fenton-like process. The combination of PAC and Fenton-like reagent has able to enhance the decolorization of black liquor up to 97%. [ABSTRACT FROM AUTHOR]

Coagulation and flocculation process was used to treat black liquor wastewater from alkali pretreatment of bioethanol production from oil palm empty fruit bunch. The optimization and the effect of pH, coagulant and flocculant dosage against decolorization, TSS reduction, final pH and sludge volume were investigated using Response Surface Methodology (RSM). Six combination were used, however, no combination gave good result to all four responses. Decolorization percentage of 99.69% was obtained by the combination of PAC and anionic polyacrylamide. The combination of alum and anionic polyacrylamide gave 91.12% TSS reduction. Final pH of 7.3 was resulted also from the combination of PAC and anionic polyacrylamide While, 50 ml sludge volume was generated from the combination of PAC and anionic polyacrylamide. From RSM with Central Composite Design (CCD) analysis, strong interaction between coagulant dosage and pH revealed to be the significant factor for black liquor wastewater treatment. [ABSTRACT FROM AUTHOR]