I. PÅ‚onka, B. Pieczykolan
Silesian University of Technology, Faculty of Energy and Environmental Engineering, Gliwice, PL


Post-coagulation sludge is generated in the technological processes of surface water treatment. This sludge is a mixture of pollutants removed from water and coagulants that was add to the water. It has a hydrophilic and colloidal character and has high hydration. The hydration of the sludge is in the range of 97-99.5% while the sludge is periodically removed from the settling tank. However, when the sludge is removed once per few weeks, the hydration may be equaled to 96%. The sludge with aluminum hydroxide is characterized by large specific surface area, thus it has low compaction susceptibility. Moreover, it has poor filtration properties and is difficult to dehydrate, because it has large compressibility and high value of the specific resistance to filtration. The flocs of the sludge have in their structure different microorganisms that are being removed directly from treated water. The number of bacteria and plankton organisms increases during blooms. The content of microorganisms in the sludge and its flocculate structure affect the amount of biologically and physically bound water, and thus it also effect on susceptibility to dehydration of the sludge. The use of disintegration process allows the destruction of cell walls of microorganisms and the release of bound water. Therefore, disintegration of the post-coagulation sludge using electromagnetic waves was conducted. The sludge was treated by microwave radiation for 30 to 330 seconds. A decrease of value of capillary suction time and the improvement of sedimentation properties were observed, in the case of disintegration process conducted not longer than 120 seconds. However, in all cases as the time of radiation increased the concentration of total solids and the value of COD in the supernatant liquid also increased.

Keywords: post-coagulation sludge, disintegration, electromagnetic waves