| The current study investigated the biochemical oxygen demand (BOD) and nitrogen removal from
actual municipal wastewater using an up-flow aerated submerged fixed-film (ASFF) bioreactor. The
experiments were conducted using a 14.8 L bioreactor with polypropylene packing media. For the
first time three kinetic models (first-order, Grau second-order, and modified Stover-Kincannon) and
evolutionary polynomial regression (EPR) were considered in evaluating the substrate removal in an
ASSF bioreactors fed with actual municipal wastewater. The applied BOD5 concentrations of actual
municipal wastewater varied in the range of 198 ± 12 to 213 ± 16 mg/L. The system was able to
achieve a 90% to 98% reduction in BOD5, while the organic loading rates (OLRs) were between 0.59
and 2.06 kg BOD5/m3.d. Disregarding certain experimental conditions, the effluent BOD5
concentrations were not more than 20 mg/L throughout the experiments. When the hydraulic retention
time (HRT) was reduced from 8 to 2.5 h, the ammonia removal efficiency dropped from 94.0% to
78.9%. Moreover, a direct relationship was observed between the applied OLR and the ratio of
volatile solids to total solids. Conversely, an inverse correlation was seen between the reduction in
total suspended solids and the OLR. Although several studies have evaluated the aerobic treatment of
different kinds of wastewaters, none of the studies contained a kinetic study relevant to ASFF
bioreactors treating an actual municipal wastewater. Among the investigated models, the modified
Stover-Kincannon and Grau second-order models were found to be the best to describe the present
system and well-fitted with the data sets |