Effect of nitrogen and phosphorus on the performance of acidogenic and methanogenic reactors for treatment of biodiesel wastewater

Abstract

A laboratory scale two-stage anaerobic process was studied in order to treat biodiesel wastewater. The first stage represented an acidogenic reactor while the second stage was a methanogenic reactor. The effect of nitrogen and phosphorus on the performance of both reactors was investigated. Biodiesel wastewater was adjusted so that its COD:N and COD:P within 100:0.1–1.1 and 100:0–1, respectively, and fed into the acidogenic reactor. After COD and pH adjustment, wastewater discharged from the acidogenic reactor was fed into the methanogenic reactor. The highest VFA concentration of 8.32 g/l was obtained from the acidogenic reactor at COD:N:P of 100:1.1:0.5. However, the highest CH4 yield of 0.170 l CH4 /g CODremoved was found at COD:N:P of 100:0.6:0.5 from the methanogenic reactor. Moreover, both nitrogen and phosphorus affected the acid composition produced in the acidogenic reactor and the long chain fatty acid consumption in the acidogenic and methanogenic reactors.

Keywords

• biogas
• acidogenic
• methanogenic
• fatty acids
• biodiesel wastewater