Cost-effective removal of water from oily sludge Whether you pump your oily sludge ashore or burn it, it's preferable to reduce the water content first. Oily sludge can contain as much as 80% water. With a Marinfloc Sludge Dewatering Unit, the amount of residual water in the sludge is reduced to a minimum. This makes it possible to burn the sludge or pump it ashore at a lower cost.