Comparison of Drying Characteristic and Biodegradability of Dairy Sludge Using Microwave and Infrared Drying

In our work we focused on the investigation of two intensive drying methods, i.e. infrared (IR) and microwave (MW) drying, for dairy sludge. During the experiments the effects of IR and MW drying with different power intensities on drying characteristic and biodegradability were examined. Our results has revealed that MW drying was more advantageous for dairy sludge, because the drying time need to achieve a certain value of final moisture content was significantly shorter than applying IR drying. Effects of increased specific power intensity could be more manifested during MW process resulted in higher drying rate. At lower power intensity MW process needed more than 30% shorter drying period to achieve the same final moisture content than the IR drying, at higher power intensity the shortening of drying time was about 70%. Considering the change in the degree of biodegradability the MW drying process has also advantages over the IR drying. Microwave dried dairy sludge has 13% higher biodegradability than that of dried by IR method, what provoke advantages for further sludge utilization processes.