Microwave Treatment for Sewage Sludge Drying
Sewage sludge samples with moisture content of 98% were dried by using laboratory scale microwave unit at
power level and exposure time of 450, 630, 900 W and 5, 10, 20, 60, 120, 240, 360 and 720 s, respectively. The data is used
to evaluate the effect of moisture content at various drying rate to achieve minimum 20% dry solid. The thermal behavior of
sewage sludge was investigated by thermogravimetric analysis. Results showed that the water content of sludge reduced
from 45.5 kg/kg to 4 kg/kg at dry basis atthe operating power level of 450 W, 630 W and 900 W at operation duration of 670,
515 and 355 seconds, respectively. The weight/volume reduction is mainly associated with the temperature increases that
resulted to the reduction of moisture content in irradiated sludge samples.Based on the findings, the optimum drying rate
obtained were 0.137 kg/kg at 900 W. Elemental contents of the dried sludge were 330.2 mg/g carbon, 108.9 mg/g hydrogen,
44.6 mg/g nitrogen and 9.89 mg/g sulfur. The calorific value of the sewage sludge was measured at 18.11 MJ/kg, which can
be potentially utilized as biomass resource for energy production.This study reveals that microwave technology could be
considered as an alternative sludge drying methodthat requires a small footprint. The reduction of weight/volumes of sludge
will reduce the cost of disposal.
Keywords - Microwave treatment, sewage sludge, moisture.