To note, a SC greater than 50 g L1 was examined in this experiment
however, incomplete mixing was observed using a magnetic
stirrer and therefore higher concentrations were not considered.
Thereafter, a DOE approach based on a 23 full factorial CCD/RSM
was conducted with three solid retention time (SRT, same with
hydraulic retention time) levels of 2, 3, and 4 days and three feed
solids content (SC) levels of 30, 40, and 50 g L1