Microwave heating analysis of waste sludge

Abstract

Sludge management is a major high-cost component for the operation of a wastewater treatment plant (WWTP). Microwave drying (MWD) can be considered as an option to reduce the total costs of sludge disposal. Microwave drying of a waste sludge originated from a biological nutrient removal plant (BNR -modified 5 Stage Bardenpho (R)) was investigated in this study. Mechanically dewatered sludge samples with 18% dry solids (DS) content were studied by using a multimode microwave applicator, with a 1kW, 2.45 GHz microwave (MW) source. Experiments were carried out under different power conditions (400-1000 W) using the same sludge mass (90 g., 18% Dry Solids). The full-wave electromagnetic fields were also simulated by using Ansoft HFSS software. The simulation results were compared with the experimental results and the results were found to be compatible. It was found that the temperature of the sludge increased as the microwave power applied increased, and that the highest temperature levels were obtained at the top of the sludge samples. Microwave heating of the sludge was found to be quicker and less expensive than conventional electric heating.