The role of C/N ratio on anaerobic decomposition of industrial tempeh wastewater for optimizing methane production

Abstract

Considering its high organic contents, A biological process, in particular anaerobically decomposition is considered to be the most suitable treatment for industrial tempeh wastewater. Among the important parameters that determine the success level of the process, C/N ratio was mentioned to play a significant role. Thus, this study was carried out to investigate the effects of different C/N ratios (10; 20; 30 and 40) on the decomposition process to produce methane gas. The experiment was conducted using 1L batch reactors with sludge from active cow manure biogas digester as inoculum. Several parameters such as pH, COD, BOD, VFAs and methane gas were monitored during the process to understand the mechanism. The experimental results confirmed that the C/N ratio significantly affected the anaerobic decomposition of tempeh wastewater, giving the best achievement for C/N = 30, with organic removal as high as 89% (COD) and total methane produced as much as 1240 mL in 14 days of observation. The balanced composition between carbon and nitrogen is important for the anaerobic process, higher organic loading (C/N = 40) will potentially lead to VFAs accumulation, meanwhile higher nitrogen concentration (C/N = 10) will stimulate complex transition, mainly denitrification and free ammonia formation. Both conditions will block the methanogenesis stage, resulting in a nonoptimal decomposition process and minimum methane production.