Effect of electromagnetic field on low dissolved oxygen wastewater treatment

Abstract

Activated sludge (AS) system is a biological treatment process that is widely applied in municipal wastewater treatment. Concentration of the dissolved oxygen (DO) is one of the important parameters that may influence the performance of AS system. Thus, certain levels of DO in AS systems should be maintained to achieve high efficiency of pollutants removal. However, the energy consumption of aeration stage represents approximately 50% of total demand of AS system. Therefore, reducing aeration energy would improve the feasibility of AS process. This study investigated the enhancement of AS process under low DO condition using electromagnetic field (EMF). The AS was exposed to EMF at intensity of 3 mT with DO concentrations of 1 and 2 mg/L for 24 hours. The impact of EMF on the biomass concentration, settling velocity, sludge volume index and pollutants removal were thoroughly investigated. The results indicated significant improvement in the physical properties of AS exposed to the EMF, which resulted with high accumulation of biomass concentration. The settling velocity and sludge volume index value of the biomass at the end of the experiment were 95 m/h and 72.6 mL/g, respectively. The reactor exposed to EMF under 2 mg/L of DO showed the highest removal efficiency of chemical oxygen demand (80%) ammonia (97%), nitrite (99%), and total nitrogen (84%). Additionally, it was proved that EMF could enhance the settleability of the AS in the treatment system.