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The objective of this research is to investigate the effects of H2S loading rate and total alkalinity on removal efficiency of high concentrated H2S obtained from biogas production from ethanol industry wastewater (molasses wastewater) by anaerobic digestion. Biogas produced from ethanol wastewater consists of 69.5-74.0 % methane, 25.3-28.1 % carbon dioxide and more 10,000 ppm hydrogen sulfide. The reactor works with combined chemical and biological processes to solve the problem of clogging of the sulfur sediment in the system. The reactor includes reaction tank, aerator tank, sedimentation tank and water tank, with the addition of Paracoccus sp. bacteria into aerator tank, filling only once at startup. The results showed that the efficiency of the removal of H2S was 99.9±0.1 %, methane was increased 12.2-16.5 % and carbon dioxide was reduced 36.6-53.2 %, in condition of the H2S loading rate at 150 and 300 g H2S/m3-h and wastewater alkalinity controlled at 4,500 mg/L as CaCO3. At the 600 g H2S/m3-h H2S loading rate and 12,000 mg/L as CaCO3 alkalinity, it was found that a trace amount of hydrogen sulfide was also simultaneously reduced to 0-18 ppm.
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