Landfarm performance under arid conditions. 2. Evaluation of parameters

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.