MECHANISM AND CONTROLLING STRATEGY OF ETHANOL FORMATION AS RECOVERY HIGH STRENGTH ORGANIC WASTEWATER

• Main Author: Andrio, David
• Format: Dissertations
• Language: Indonesia
• Subjects: Teknik saniter dan perkotaan; teknik perlindungan lingkungan
• Online Access: https://digilib.itb.ac.id/gdl/view/80718
• Institution: Institut Teknologi Bandung

One alternative to overcome limited sources of raw materials which are not classified as human food inethanol industries in Indonesia is to utilize high strength organic wastewater from agro industrial activities through acidogenesis process. Ethanol formation can divided into two pathways, namely a direct and an indirect conversion of pyruvic acid to acetaldehyde. Microorganismsproducing pyruvate decarboxylase enzymes convert pyruvate to acetaldehyde directly, while in anaerobic bacteria pyruvate is converted firstinto acetyl-CoA, then into acetaldehyde, and also into volatile acidswhich could reduce ethanol formation. The objectives of this research were to study the mechanism of ethanol formation and the shift of acidogenic products formation from artificial organic wastewater and palm oil mill effluent through the operational control of circulating bed reactor. Optimization ofethanol formation through pH control, substrate sterilization influent, N2 flushing at several rates and addition of Fe2+ and Zn2+at various different concentrationshave been performed in this study. The obtained optimum conditions were thenapplied in the palm oil mill effluent. Moreover,isolation and identification of bacterial consortiumfrom reactor at optimum condition for ethanol formation have been conducted. The initial pH for all reactorswere set in the range of 6-6.5 and the reactor weremaintained at similar pH range. Ethanol concentrations at pH controlled and non-pH controlled reactorswere 48.32 and 50.22 mgCOD/L or 23.12 and 24.23 mg/L, respectively, andit was found that at pH controlled and sterile substrate reactors produced similar ethanol concentration, (48.70 mgCOD/L or 23.30 mg/L). Control of pH and substrate sterilization could increase acetate formation and inhibit the lactate formation. As a comparison ethanol produced by Saccharomyces cerevisiaereactor was also investigated. As expected the S. cerevisiae reactor produced ethanol with concentration of 60.91; 71.29and138.94mgCOD/L or 29.14; 34.11 and 66.47 mg/L for non-sterile substrateswithout,andwithcontrol,andthesterilesubstratereactorwithpHcontrolsequence, subsequently. Biodegradation of artificial organic wastewater under N2flushingat 0.0; 0.15 and0.2 L/min/Lliquidproducedethanolwith concentrations of 44.09; 40.10; 27.17mgCOD/L or 21.10; 19.19 and 13.00 mg/L, respectively. N2flushingcan increase aceticacidformation by reducinglactate, propionateandbutyrate synthesis. To increase the formation of ethanol, the additions of Fe2+at concentrations of 40; 50; 100; 200 and 400 mg/L, and Zn2+ of 0.5; 1.0; 1.5; 2.5 and 5.0 mg/L with N2flushing at 0.2 L/min/Lliquidhave been carried out. The highest ethanol concentration was obtained in reactor containing 40 mg/L Fe2+ with ethanol concentration of 512.23 mgCOD/L or 245.09 mg/L, and the highest ethanol concentration with the value of 289.89 mgCOD/L or 138.70 mg/L was obtained in the presence of 1.5 mg/LZn2+. Taken together the optimum condition for ethanol production in artificial organic wastewater was at 0.2 L/min/LliquidN2 flushing, 40 mgFe2+/L, and 1.5 mgZn2+/L addition. The optimum condition obtained from artificial organic wastewaterwas applied to the palm oil mill effluent. Ethanol concentration produced in reactor flushed with N2at the rate of flushing0.2 L/min/Lfluidwas 749.51 mgCOD/L or 358.62 mg/L, while ethanol concentration in reactor without flushing was 324.88 mgCOD/L or 144,45 mg/L.The addition of Fe2+ at 40 and 50 mg/L resulted in ethanol formation of 1614.87 mgCOD/L or 772,66 mg/L and 907.82 mgCOD/L or 434,36 mg/L, respectively. The addition 0.5 mgZn2+/L in the presence of 40 mgFe2+/L increased the ethanol concentration with the value of 1840.24 mgCOD/L or 880,50 mg/L. Moreover,the addition of 50 mgFe2+/L + 0.5 mgZn2+/L led to further increase of ethanol formation with concentration of 2267.29 mgCOD/L or 1084,83 mg/L.