No abstract

No abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSaudi Arabia is a major oil exporting country in the world with average production of approximately eight million barrels of crude oil every day. As a result of its operation, Saudi Aramco generates more than 30,000 cubic meters of oily sludge every year. The main disposal method for oily sludge in the Kingdom is landfarming, which is an attractive method due to the hot arid climatic conditions. Although landfarming technology was introduced to Saudi Arabia in 1982, the decision to use this technology was based on information obtained through studies conducted in other countries mainly in relatively cold climatic conditions. No scientific studies and/or research were conducted within the Kingdom of Saudi Arabia to support this decision.A field-scale study was conducted in the Juaymah area in the Eastern Province of Saudi Arabia to study the degradation of petroleum hydrocarbons under natural and enhanced conditions using landfarm and bioreactor technologies. The results presented in this paper are based on a comprehensive field experiment conducted under Saudi Arabian environmental conditions. Details of experimental setup and conceptual framework of degradation process based on field observations are presented. The paper also addresses kinetics of oily sludge degradation in landfarm and bioreactor cells under natural and enhanced conditions in the presence of water, nutrients and tilling. The results of this study revealed that weathering (evaporation) and not biodegradation was the dominant degradation mechanism. The results also showed that tilling was the main operating parameter responsible for achieving the highest percentage of reduction (76%) in the O&G concentrations in landfarms. The analytical results also revealed that due to the method of air addition, the bioreactor system was not effective in achieving a high percentage of O&G reduction.

Various parameters that influence the degradation processes in landfarming operations include moisture content, microbial density and composition, nutrients, and tilling. In this paper, a detailed evaluation of each parameter is presented based on field experiments. This paper also addresses kinetic of weathering, volatilization, and biodegradation mechanisms under natural attenuation and enhanced conditions including aeration in the soil pores by tilling; combined effects of tilling and nutrients in the soil; tilling and addition of waterto maintain a minimum moisture level; and combination of tilling, water, and nutrients. The effect of double loading under enhanced condition was also studied in this paper. The study shows that the tilling is very effective to to enhance the loss of oil and grease (O&G) fractions under arid conditions. However hydrocarbon loss in the absence of fertilizer and water was mainly due to weathering (volatilization). In the absence water and nutrients, the microbial counts were found to be low. The addition of water and fertilizer combined with the tilling helped in the significant reduction of O&G through both volatilization and biodegradation mechanisms with early reduction of n-alkanes through a biodegradation process followed by weathering. However, in order to determine the contribution of each of these two processes to the whole degradation, further work is required. The high loading rate resulted in retaining moisture content in the soil, and it delayed weathering and biodegradation. The high loading rate caused bacterial counts to increase, as it provided them with a plentiful source of food and water; however, it did not stimulate the biodegradation process for almost 6 months after the highest rate of sludge application to the soil.

The primary disposal method for oily sludge in the Kingdom of Saudi Arabia, which is a major oil-exporting country in the world, is landfarming. It is an attractive method of oily sludge disposal in hot arid climatic conditions. Although landfarming technology was introduced to Saudi Arabia in 1982, no scientific studies have been conducted within the Kingdom to support this decision. The results presented in this paper are based on a comprehensive field experiment conducted under Saudi Arabian environmental conditions. Details of experimental setup and conceptual framework of degradation process based on field observations are presented in this paper. The paper also addresses kinetics of oily sludge degradation in landfarm cells under natural and enhanced conditions in the presence of water, nutrients, and tilling. The 12-month field study showed that weathering (evaporation) and not biodegradation is the overall dominant degradation mechanism occurring in landfarms in the study area. The results of this study showed that up to 76% of the oil and grease (O&G) in the sludge has been lost from soil as a result of weathering. However, the results of this study also indicated the primary mechanism for the loss of C17 and C18 alkanes as compared to branched alkanes was due to biodegradation.