Biological Treatment of Oily Sludge and Sediments
Oily sludge, generated in refineries or in other industrial sectors, and oil-containing sediments, removed from water bodies during remediation works, pose an environmental problem. A common feature between both is their high water content, and variable content of organic and inorganic contaminants, which complicates their treatment. The overall objective of this thesis was to contribute to the development of environmentally sound and cost-effective methods for biological treatment of oily sludge and oilcontaining sediments. Two materials were treated: (i) oily sludge from a flocculationflotation unit (FFU) of a refinery in Sweden and; (ii) oil-containing sediments from an oily leachate pond in Estonia. Experiments with sludge compost were made in 1-m3 and 28-m3 scale in bioreactors, simulating composting in static biopiles. In parallel to field studies with sediment compost, a laboratory experiment was conducted. In all experiments, semi-liquid oily waste was amended with various amendments to adsorb
liquids, adjust nutrients, and add porosity. The monitoring period, chosen to follow the fate of petroleum hydrocarbons and individual PAHs was relatively long, 1221 months. It was found that organic amendments can contribute to the pollution load in a mixture, particularly heavy metals and PAHs. If these are limiting compounds, inert inorganic
bulking material should be used instead, as long as requirements for microbial metabolism are fulfilled. In this case, the degradation of the target contaminants in oily sludge will explicitly be monitored. Although seen as cost effective and relatively simple to design, install and operate, static biopiles can yield variable results in the extent of hydrocarbons degraded. As observed, spots with high concentrations can remain, as a result of either initially present hydrocarbon-saturated clumps or, as recorded, by unfavourable environment for degradation due to preferential channelling of airflow and replacement of moisture through the biopile. Static biopile technology was found to be effective during the first 24 months of treatment, after which the material should be removed from biopile, and mechanically mixed for maturation in windrows. Therefore, low-tech windrow-composting might be combined with forced aeration if solid phase degradation of semi-liquid wastes is targeted.
flocculation-flotation unit (FFU)
13.00 VK-salen, Sven Hultinsg. 6, Chalmers
Opponent: Professor Rune Bakke, Telemark University College, Faculty of Technology, Norway