This work aims to control foaming in a submerged membrane bioreactor (SMBR) by optimizing
the organic loading rate (OLR) and sludge retention time (SRT) values to decrease the extracellular
polymeric substance (EPS) production used for the pharmaceutical wastewater treatment. Four
lab-scale SMBRs were operated for a period of more than 8 months to determine the biokinetic coefficients and optimize the SMBR systems operation under the SRT of 5, 10, 15, 20, 25 days and OLRs of 0.03-0.32 gCOD/L.day. The investigation revealed that the lowest foaming quantity was at an organic loading rate of 0.32 gCOD/L.day and a sludge retention time of 15 days related to few protein concentration of EPS. The results also showed that the foaming quality at the OLR
of 0.03 gCOD/L.day was higher compared to the greater OLRs in all SRTs. It was found that the
yield (Y), the endogenous decay coefficient (kd), the maximum specific growth rate (μmax), and the
saturation constant (Ks) of four SMBRs were in the range of 73.53-232.55 mg/mg, 1-3.156 day-1,
1.269-3.708 day-1, and 2.57-145.8 mgCOD/L, respectively. Furthermore, the most appropriate
operating condition to activated sludge among the SMBRs was the OLR of 0.1 gCOD/L.day and
SRT of 15 days. Under these optimum conditions, a 92.8% COD removal efficiency and 3.708
1/day μmax were achieved.