The disposal of large amounts of sludge, deposited in many farm/irrigation ponds in Japan, has recently become an important task to be resolved. To dredge sludge helps to maintain the capacity of the ponds and the quality of the water in the pond. In other words, it is vital that the deposited sludge should be effectively dredged. Since the water content of dredged sludge is very high, it must be reduced to enable the transport and the reuse of the sludge. The authors of the present paper have developed a procedure to dehydrate in-situ dredged sludge from farm ponds using a compact filter press machine. The purpose of this study is to investigate appropriate conditions for the efficient dehydration of dredged sludge with a compact filter press machine. Since the dehydration mechanism inside the filter press machine is based on the hydraulic consolidation, hydraulic consolidation tests are conducted to simulate the filter press consolidation in order to clarify the relationship between the conditions of the filter press dehydration and the water content of the consolidated sludge. Results of the tests show that the most important factor in controlling the efficiency of the actual filter press dehydration process is the thickness of the filtration chamber of the filter press machine. Sludge is expected to be more effectively dehydrated when a filtration chamber with a smaller thickness is adopted.