Long-term performance of a land treatment facility for the bioremediation of non-volatile oily wastes

The current study reports on operational and performance aspects of a land treatment facility for managing oily wastes generated from heavy vehicle ma intenance over a 5-year period. Samples of soil and groundwater from the la nd treatment plots were analyzed for a range of contaminants and microorgan isms over this period. The soil analyses indicated that the process has bee n operating efficiently even at high wastewater loadings with maximum degra dation rates of 250 mg/kg per day (year 1) and average rates of 10-35 mg/kg per day (years 2-5). Hydrocarbon degraders comprised more than 80% of the total (measured) soil heterotrophic population and were present at 10(6)-10 (8) (per gram soil) once the process was optimized. The facility was capabl e of treating 140 kl of oily wastewater per day (average petroleum hydrocar bon content of 2% w/v) over the entire period. During this time there was n o evidence of accumulation of any major metals or polycyclic aromatic hydro carbon (PAH) compounds in the soil. Groundwater sampling and analysis indic ated that the land treatment facility was not leading to contamination of a ny groundwater taken from bores in the vicinity of the facility. The land t reatment process continues to be effective for treatment of non-volatile wa ste oils at this remote and high evaporation (arid) site. (C) 2000 Elsevier Science B.V. All rights reserved.