“…It consists of modified mathematical models to introduce biological parameters into the model. Numerous models have been used to evaluate cumulative methane production (Gioannis et al, 2009;Lo et al, 2010;Pavlostathis and Giraldo, 1991;Altas, 2009;Manjula and Mahanta, 2014;Li et al, 2012;Jagadish et al, 2012;Kafle and Chen, 2016;Kurtgoz et al, 2018;Antwi et al, 2017;Nair et al, 2016). Altas (2009) emphasized on the effect of heavy metal inhibitors (Cr, Cd, Ni and Zn) on anaerobic granular methane-producing sludge.…”