Application of dielectric constant measurement in microwave sludge disintegration and wastewater purification processes

Abstract

It has been numerously verified that microwave radiation could be advantageous as a pre-treatment for enhanced disintegration of sludge. Very few data related to the dielectric parameters of wastewater of different origins are available; therefore, the objective of our work was to measure the dielectric constant of municipal and meat industrial wastewater during a continuous flow operating microwave process. Determination of the dielectric constant and its change during wastewater and sludge processing make it possible to decide on the applicability of dielectric measurements for detecting the organic matter removal efficiency of wastewater purification process or disintegration degree of sludge. With the measurement of dielectric constant as a function of temperature, total solids (TS) content and microwave specific process parameters regression models were developed. Our results verified that in the case of municipal wastewater sludge, the TS content has a significant effect on the dielectric constant and disintegration degree (DD), as does the temperature. The dielectric constant has a decreasing tendency with increasing temperature for wastewater sludge of low TS content, but an adverse effect was found for samples with high TS and organic matter contents. DD of meat processing wastewater sludge was influenced significantly by the volumetric flow rate and power level, as process parameters of continuously flow microwave pre-treatments. It can be concluded that the disintegration process of food industry sludge can be detected by dielectric constant measurements. From technical purposes the applicability of dielectric measurements was tested in the purification process of municipal wastewater, as well. Determination of dielectric behaviour was a sensitive method to detect the purification degree of municipal wastewater.

Detection of efficiency of microwave-enhanced sludge treatments by dielectric measurements

“…The results of dielectric measurement show that the ratio of dielectric constant (300MHz/2400MHz) has a linear correlation with the SCOD/TCOD in both treated materials, respectively: shows that the applied power intensity and the type of treated material affect the regression equations, but the presented correlation is independent from these factors. The higher organic matter solubility can be traced back to the degradation effect of the MW on the solid particles and the macromolecules of the sludge, causing deflocculation [12].…”

“…Measuring dielectric properties is a rapid, non-destructive way of determine structural and/or molecular changes in the raw material matrix, and such, it is a suitable method to detect the organic matter removal efficiency of wastewater treatment processes [11,12].…”

“…shows that the applied power intensity and the type of treated material affect the regression equations, but the presented correlation is independent from these factors. The higher organic matter solubility can be traced back to the degradation effect of the MW on the solid particles and the macromolecules of the sludge, causing deflocculation[12]. As the indicator of aerobic biodegradation, the ratio of BOD and COD were determined (Fig.2).…”

Possibilities for detection of the change of biodegradability of wastewater by dielectric constant measurements

“…These effects are manifested in higher organic matter solubility. With the decreasing of molecular weight of wastewater components, and the disintegration of particles the polarization ability of electromagnetic field is improved, which can be detectable by the change of dielectric constant [3,9].…”

Mikrohullámú energiaközléssel kombinált Fenton-eljárás hatékonyság-vizsgálata a szennyvíztisztításban

“…A veszteségi tényező és a dielektromos állandó hányadosa adja az úgynevezett veszteségi szög tangensét (tanδ) (Clark et al, 2000). Egy adott frekvencián a dielektromos paraméterek értéke függ az anyag hőmérsékletétől és fizikokémiai struktúrájától, ezáltal alkalmasak egyes fizikai és kémiai változások detektálására is (Kovács et al, 2018).…”