**3. Conclusion**

soil compost which was impossible in the columns. The compost windrows were turned at least once per month in the composting facility and therefore the leaching of petroleum hydrocarbons and non ionic surfactant would not occur. After the experiments the fractions

**H2O Tween 80**

**Time, days**

1-23 238 105.4 15 1-22 238 97.7 10 2.9 24-40 136 94.8 11 23-34 102 96.0 10 20.9 41-51 136 105.6 10 35-48 136 102.7 10 25.1 52-68 102 87.4 13 49-64 102 74.1 70 85.1 **1-68 612 393.2 12 1-64 578 370.5 22 30.2**

**Added water, g**

**TPH, g HEM kgˉ<sup>1</sup>**

**Initial** 462±3 77.3±2.1 0 6.92 0.27 **Compost + H2O 0–16** 358±11 61.6±5.2 0 7.13 0.46 **16–32** 307±8 55.4±4.2 0 7.12 0.33 **32–48** 375±14 64.2±4.2 0 7.47 0.48 **Compost + Tween 80 0–16** 213±48 61.6±5.7 8.7±0.8 8.30 0.33 **16–32** 239±16 61.1±5.2 26.1±2.5 8.01 0.32 **32–48** 299±25 55.9±5.3 52.3±4.2 7.87 0.30

The analysis of compost fractions showed that both water and solution of Tween 80 reduced the content of petroleum products in the compost mixture about 20%. The reduction of hydrocarbon content was generated through biodegradation as less than 0.01% of hydrocar‐ bons were leached out from the soil columns. It is important to note that addition of surfactant did not increase the leaching of petroleum products [112]. In the column of soil compost which was treated with water the lowest TPH content as well as rate oxygen demand and conductivity were determined for the centre fraction (16-32 cm). In the case of treatment with Tween 80 the rate of oxygen demand was the highest for the lower fraction, but content of TPH was lightly higher for the upper layer. The analyses of soil compost fractions showed that non ionic surfactant was leached into the lower fractions of soil (Table 5) and only up to 10% of non ionic

**Solid soil compost Water extract of soil compost**

**Leachate, g TPH,**

**mg HEM Lˉ<sup>1</sup>**

**pH EC,**

**mS cmˉ<sup>1</sup>**

**Surfactant, mg CTAS Lˉ<sup>1</sup>**

**Surfactant, mg CTAS kgˉ<sup>1</sup>**

of soil compost were analyzed and the results are presented in Table 5.

**Table 5.** Characteristics of fraction of soil compost after leaching experiments in the columns

surfactant was leached out from the soil columns during 60 days.

**Rate of oxygen demand, mg O2 kg ˉ<sup>1</sup> hˉ<sup>1</sup>**

**Table 4.** Leachate from the column of composted soil

134 Applied Bioremediation - Active and Passive Approaches

**Leachate, g TPH,**

**mg HEM Lˉ<sup>1</sup>**

**Compost fraction, cm**

**Time, days**

**Added water, g**

> Surfactants are used to increase the bioavailability of hydrophobic pollutants (hydrocarbons), but the added anionic surfactants were washed out of the upper layer of soil columns during the first 30 days regardless of the type of soil. After the experiments (60 days), the analysis of different soil fractions showed that up to 86% of anionic surfactants had degraded in the column of coarse-grained polluted soil while up to 28% of the added surfactants had degraded in the column of fine sandy soil. Higher amount of anionic surfactants was determined in the leachate of columns of coarse-grained soil and the higher porosity of soil could increase the leaching of surfactants due to the lower surface area of coarse-grained soil.

> Addition of porous urea-formaldehyde adsorbent increased the mass of generated leachate (up to 25%) due to the higher porosity of soil but anionic surfactants were no leached out and the analysis of soil fractions indicated no significant accumulation of anionic surfactants in the upper layer of mixture of soil and adsorbent.

During the experiments similar amounts of leachate were generated from the soil compost through the addition of non ionic surfactant Tween 80 or water and therefore the non-ionic surfactant did not increase the amount of leachate during 2 months. The leachate had quite low content both of TPH and non ionic surfactant, but it was increased significantly for the last period through the added Tween 80, therefore the added non ionic surfactant can generate the leaching of petroleum hydrocarbon during longer period of treatment.

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The analysis of compost fractions showed that both water and solution of Tween 80 reduced the content of petroleum products in the compost mixture about 20% and the reduction of hydrocarbon content was generated through biodegradation as less than 0.01% of hydrocar‐ bons were leached out from the soil columns.

Calculation of mass balance of anionic surfactants showed 86% of degradation of anionic surfactants in the column of coarse-grained oil-polluted soil, while 72% degradation of TPH was determined for the mixture of polluted coarse soil with adsorbent treated solution of anionic surfactants. Calculation of mass balance indicated that 43% of non ionic surfactant Tween 80 was degraded during 60 days of experiments in soil compost, but non ionic surfactant had no accelerating effect on the biodegradation of TPH in soil compost.
