Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a pilot-scale study)

Abstract In this study, the effect of static magnetic fields (SMFs) on improving the performance of activated sludge to enhance the microbial growth rate and improve sludge settling characteristics in real operation conditions has been investigated. The effect of SMFs (15 mT), hydraulic retention time, sludge age, aeration time on mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids (MLVSS), α-factor, and pH in the complete-mix activated sludge (CMAS) process during 30 days of operation were evaluated. There were not any differences between the concentration of MLSS in the case and control samples, however, the mean concentration of MLVSS in the case (1463.4 ± 419.2 mg/L) was more than the control samples (1244.1 ± 295.5 mg/L). Changes of the concentration of MLVSS over time, follow the first and second-order reaction with and without exposure to SMFs respectively. however, the slope of the line in the case samples was 6.255 higher than in the control samples. The mean of α-factor in the case samples increased by -0.001 higher than in the control samples. Changes in pH in both groups of the reactors were not observed. 15 mT intensity of SMFs can promote oxygen transfer to the biomass and, increase the concentration of MLVSS in aeration reactor of CMAS. SMFs have a potential to consider as an alternative method to stimulate the microbial growth rate in the aeration reactor and produce bioflocs with higher density in CMAS.