Electromagnetic Stimulation of Microbial Activity in Wastewater Treatment: Experimental Equipment

Abstract

A system for electromagnetic stimulation of microorganisms' activity from the active sludge of wastewater treatment plants was developed and preliminarily tested. Through electrochemical, gravimetric, XRD, and SEM-EDAX measurements, it was found that austenitic stainless steel 18/8 presents good stability to AC polarization in wastewater. Preliminary determinations performed through the dielectric spectroscopy technique indicated that the activated sludge's microbial flora is sensitive to 50 ± 0.1 Hz. The stimulation system developed and put into service on the biological aerobic treatment bioreactor consists of a pair of polarizing electrodes, made of perforated 18/8 stainless steel sheet, electrically connected to a power supply, which at 50 Hz is capable of debiting adjustable voltages between 5 and 24 Vrms at a maximum current of 5 A. Preliminary in situ measurements showed that following the stimulation of the microorganisms from the sludge suspension, as a result of an applied electromagnetic field of approximately 4.5 V/m at 50 Hz, the metabolism of residues is accelerated substantially (organic residues determined by oxygen demand decrease by about 42 %, nitrogen/ammonium content by about 44% and total phosphorus by about 50 % which results in an increase in free oxygen concentration by about 71 %).