ISWR Home

Monash University > Engineering > Institute for Sustainable Water Resources > Research > Projects > Dewatering of sewage sludge

Print version

Dewatering of sewage sludge using mechanical thermal expression (MTE)

The purpose of this research project is to develop a process for dewatering of semi-dried biosolids and digested sludge and work with industry to demonstrate the process.

Digested sewage sludge is the freshly generated material from various wastewater treatment phases and it contains approximately 98% water. When the digested sludge sits on the evaporation ponds or drying beds for a few years, it undergoes physical and chemical changes becoming biosolid which is a nutrient-rich organic material and contains approximately 50% water.

The main research objectives are:

1. Determine the reason for the difference in dewatering behaviour of semi-dried biosolids and digested sludge.
2. Investigate how to accelerate the aging process.
3. Determine the specific components responsible for the poor dewatering characteristics of digested sludge and determine how to improve its dewaterability.
4. Determine how to increase the calorific value of the MTE product.
5. Develop a treatment process to reduce the ash content of biosolids.

Research Team
Khagendra Thapa, Dr. Andrew Hoadley, Dr. Sam Clayton, Dr. Gavin Mudd

Industry Adviser
GHD: Dr. Robbert van Oorschot

Outcomes to date
To be posted.

Presentations
Investigation of MTE for ‘difficult to dewater materials’.

Journal and Conference Papers
Sam A. Clayton, Andrew F.A. Hoadley, Oliver N. Scholes and Rory Wheeler, (2004) ‘Investigation of MTE for ‘Difficult to Dewater’ Materials’,10^th APCChe Congress: Earth sustainable technologies – chemical engineers challenge, Kitakyushu, Japan, October, 2004.

MTE Process
Figure 1 presents a schematic of the MTE process. The test sample is compressed in a cylindrical metal cell by application of mechanical force which is generated using an INSTRON pressing device. The force is applied through a piston to the sample, resulting in water being squeezed out of the sample. The expressed water passes through a filter medium and out of the cell. Computer software is used to set the desired applied pressure (maximum 25MPa) and to records the data. A band heater is also used for elevated test temperatures of up to 200^oC.