MOBILITY OF OIL AND OTHER SLUDGE CONSTITUENTS DURING OILY SLUDGE TREATMENT BY LANDFARMING

Five levels of oily sludge application were made to the surface layer of a desert sandy soil in Kuwait. The migration of the constituents of the sludge to subsurface soil layers was investigated at intervals ov er a period of 29 months. The data show very limited mobility to subsu rface soil layer (40-70 cm depth) but not to 70-90 cm depth. The envir onmental impact of the added sludge is related to soil pH and to the Z n equivalent value of the sludge. Zn equivalent for the soil treated w ith oily sludge was 612 mg kg-1, which is much lower than permissible limits. This soil can accept more than 1000 t ha-1 from this type of s ludge. However, due to the heterogeneous composition of sludge the Zn equivalent value should be calculated for each batch. Addition of oily sludge to the desert soil susceptible to wind erosion had a significa nt effect on minimizing soil loss under wind tunnel conditions. This e ffect is attributed to aggregation of the soil particles in the surfac e soil layers.