The Impact of the Cutting Oil Waste Discharges on the Activated Sludge Centrifugal Dehydration

This research examines the impact of cutting oil waste (COWE) from the metallurgical industry on the centrifugal dehydration process of activated sludge. It is crucial to treat these industrial discharges in situ, either through biological processes or physio-chemical methods, before directing them towards surrounding ecosystems or urban wastewater plants. Various treatments generate sludge that retains a significant proportion of these oils. We investigated the effect of three types of cutting oils on the centrifugal dehydration of activated sludge collected from a biological reactor. These types include cutting oils in their raw state and prepared at a concentration of 4% (COWE1), used oils (COWE2), and oils stored after use (COWE3). COWE1 presents an organic load of 29.246 g. L^-1 of COD_T, decreasing by 27% after use and 41% after storage. These oils demonstrate biodegradability measured by respirometric tests, expressed by the maximal exogenous respiration of 24.6, 6.906, and 3.222 mg. L^-1.h^-1 for COWE1, COWE2, and COWE3, respectively. The latter reduces the efficiency of the centrifugal dehydration of activated sludge, reaching 21.44%, as evaluated by the percentage of solid cake.