|
|
|
EFFECTS OF OZONE TREATMENT ON THE SOIL ORGANIC MATTER ON CONTAMINATED SITES G. Ohlenbusch, S. Hesse, F. H. Frimmel Abstract:In recent years, the ozone treatment technique has been discussed for remediation of contaminated sites. In this paper, data on the effects of ozonation of soil organic matter in ground and pore waters are presented. An aqueous soil extract was ozonated in a stirred tank reactor and characterized by size-exclusion chromatography with online UV and dissolved organic carbon detection. Additionally, degradation experiments were carried out with these extracts in a bacteria regrowth measurement system. After ozonation, a decrease of the humic acid fraction and a reduction of its average molecular size could be recognized. In contrast to this, there was an increase of the building block fraction and the low molecular acid fraction. These two fractions were readily degradable by microorganisms. Therefore. the bacteria regrowth increased with ozonation time. As a result of this, a fist and high regrowth of bacteria can be expected after the ozonation remediation technique has been applied. The UV absorbance of extracts at a wavelength of 254nm showed no significant changes before and after biological degradation. It can be supposed that the microorganisms were not able to degrade chromophoric groups absorbing at a wavelength of 254 nm. Materials and Methods: Soil containing organic C-content of 1.34 +/- 0.14 mass percent, pH value of 6.6 and a maximal water retention capacity of 35.3 grams per 100 grams dry mass were ozonated. The ozone values were 20 liters/hr with a concentration of 7 mg/l. Conclusions: Ozonation leads to a decrease of the humic acid fraction and a shift of its maximum towards longer retention time. This means that a reduction of the average molecular size of this fraction took place. On the other hand, there was an increase of the building-block fraction and the low molecular acid fraction. These products show a good microbial degradability. This can lead to a fast and high bacteria regrowth after ozonation of a contaminated site. There might be a special lagphase and a selection of bacteria during this regrowth process. Further on, there is a high decrease of UV absorbance (254 nm) during ozonation. This is caused by a preferred oxidation of chromophores. In the biological degradation experiments, there was no great difference between UV absorption before and after microbial degradation. That means bacteria were not able to degrade these chromophoric structures, or less likely new chromophores were synthesized with a similar rate as the one of their degradation. | |||||
|
The largest supplier of ozone
equipment on the web. See our New Site www.ozonesupplies.com |
