Research On Remediation Of Petroleum-contaminated Soil By Bioventing And Composting Technology

A simulation study was carried out on the bioremediation of petroleum-contaminated soilin laboratory through column-experiments by bioventing and composting technology in thispaper. The experiments of composting of dewatered sewage sludge added as compost materialwith diesel oil-contaminated soil and organic fertilizer added as compost material with crudeoil-contaminated soil were conducted respectively based on the venting experiment of dieseloil-contaminated arenaceous quartz. This study came to the main conclusions as thefollowing.⑴The total removal ratios of the oil contaminants were obtained afer a period ofcomposting with contaminated soil and compost materials at different mixture ratios under thecondition of room temperture and forced venting. The removal ratio of diesel oil reached toover 64% of the initial diesel oil content after 45 days, while the initial diesel oil content was5.00×104mg·kg-1. The removal ratio of crude oil reached to over 45% of the initial crude oilcontent after 40 days, while the initial crude oil content was about 7.00×104mg·kg-1. Thesetwo results were both higher than that were in the control experiments (49.56% and 18.62%,respectively). The relatively high total removal ratio of the oil contaminants by thistechnology was confirmed in comparison with the results of some other researchers.⑵ Biodegradation was the main way of the oil contaminants removal. Thebiodegradation ratio was about 96% in the total removal ratio, while the volatilization loss ofthe oil contaminants was only about 4%. The volatilization componentsof oil mainly includedthe hydrocarbon compounds of C9～C16. Biodegradation of the oil contaminants could beproved by the variety of the oil components content in compost and active carbon.⑶In the two groups of experiments, the relatively high total removal ratio and the mostcomplete biodegradation of the oil contaminants were observed in the experiment at the ratioof 7:3 of contaminated soil to compost material on dry weight basis in three experiments atthe ratios of 8:2, 7:3 and 5:5 respectively. This conclusion had an important significanceconsidering engineering and technology.⑷The correlation coefficients for the kinetic models indicated that the first order modeldescribed the biodegradation of oil with high correlation coefficients. The first orderdegradation rate of diesel was 0.0205d-1 in the experiment at the ratio of 7:3 of contaminatedsoil to compost material on dry weight basis, which was 1.34 times higher than that in thecontrol experiment (Kt=0.0153d-1);The half-life of diesel oil was 33.81d while it was 45.30din the control experiment The first order degradation rate of crude oil was 0.0175d-1, whichwas 3.72 times higher than that in the control experiment (Kt=0.0047d-1). The half-life ofcrude oil was 39.61d, and it was about 1/4 of which in the control experiment (t1/2=147.5d).⑸Both the dewater sewage sludge and the organic fertilizer used in the experimentswere proved to be appropriate materials for composting. The addition of these two kinds ofmaterials both accelerated the biodegradation of petroleum.⑹High correlations were found among petroleum biodegradation rate and the amount ofCO2 evolved, and the latter was also a direct proof of the biodegradation of the contaminants.Both of these two kinds of indexes could indicate the effect of bioremediation directly.