Integrated Disposal Scheme of Heavy Fuel Oil Flyash in Saudi Arabia

Heavy fuel oil is used in power production and water desalination plants, which results in producing large amounts of flyash that needs to be utilized or at least managed properly. If disposed in landfills, heavy fuel oil flyash (HFOF) may have detrimental effects on surrounding environments, particularly, ground and surface waters. Therefore, HFOF must be subjected to leaching tests prior to its disposal in landfills in order to design landfills in proper-engineered manners. In the current research, HFOF samples produced by plants firing heavy crude oil were subjected to heavy metals leaching tests in order to investigate its potential environmental hazards. Water extraction, toxicity characteristics leaching procedure (TCLP) and leaching sand columns were used to investigate the leaching of heavy metals from the collected flyash samples. Results of water extraction indicated that concentrations of metals such as chromium, nickel and vanadium, in the extract, were in the range of 1.89-30.5, 55.9-2113 and 270-6260 mg/l, respectively. Moreover, results of the TCLP showed that cadmium, chromium, nickel, and vanadium exceeded the regulated concentration. Nickel and vanadium were found to be more than 45 and 700 times, respectively, higher than the regulated concentrations. The leaching sand-column investigation clearly indicated that there are major concerns with the leachate of chromium, nickel and vanadium. Based on the results, an integrated disposal scheme of HFOF was proposed in order to minimize negative effects on surrounding environments.