# Bioremediation of Hydrocarbon-Polluted Soil: Evaluation of Different Operative Parameters
## 2 Materials and Methods
### Experimental Setup
#### 2.3.2 Test B  
This test was carried out inside an industrial warehouse, roofed, with a concrete floor, and provided with open windows, adapted as an experimental polygon for research at bench scale. Here, 24 experimental biopsies were prepared within identical polyethylene basins with dimensions of 1.10 m long and 0.95 m wide. Each basin, acting as a container, was separated from the surrounding ones to avoid the mix of materials and leakage. The moisture content was checked every 4 days, and every two weeks the processing material was homogenized in its basin with manual means, to achieve aeration of the mixture.  
The layout of the experimental units was selected using a simple random procedure, assigning a randomized number to each biopile that matched a specific position in the experimental polygon area. The distribution is shown in Figure 2.  
The biopiles were set up taking into account both the technical and logistical necessities deployed by [PERSON] et al. [40] and the guidelines for construction design of typical biopiles given by EPA [41]. Each biopile was shaped like a truncated pyramid, with a height around 0.2 m and an angle of about 45\({}^{\circ}\) between the lateral pyramid faces and the lower base. The starting total mass of each biopile has been chosen equal to 38 kg, corresponding to 30.3 kg of soil, 3.04 kg of additive bulking agent, and 4.66 kg of oily sludge. The initial TPH concentration of each experimental unit was estimated equal to 9.57 g\(\cdot\)kg\({}^{-1}\) of the mixture (soil, hydrocarbons, and additive bulking agent of wet base), calculated by mass balance from the composition of the ingredients. In each biopile, the ratio C/N was equal to 10, according to the criteria given by EPA [41]. This parameter was achieved by dosing a solution containing urea and ammonium nitrate and mixing it with the processing material.  
The water content for all the experimental units was fixed at 20% by weight. Details of the biopile design are given in a previous paper [42].  
The pH was kept in the range 6-8, while the temperature was in the range 16-30 \({}^{\circ}\)C, according to the seasonal temperature in Cuba, as reported in a previous study [43]. Monitoring of temperature, pH, and water content, as well as homogenization, aeration, and handling procedures, were previously described [33].  
A typical greyish-brown soil from the central region of Cuba was used (density = 1190 kg\(\cdot\)m\({}^{-3}\)). For the soil classification, the Cuban standards [44; 45] based on ASTM D 422-63 (Standard Test Method for Particle-Size Analysis of Soils) and ASTM D2487 (Standard Practice for Classification of Soils for Engineering Purposes) were applied. The soil was classified as silty-clay-sand with low plasticity and moderate permeability. The soil was sieved using an industrial mesh for particles smaller than 4.75 mm, according to the previously mentioned Cuban standards.  
As aforesaid, as a pollutant for the biopiles, an oily sludge deriving from the settler of a Cuban refinery wastewater treatment was chosen. Due to its hazardous, the sludge cannot be disposed in the environment, as imposed by the national standard [46].  
For the sake of clearness, Table 1 reports the information for both tests.  
Figure 2: Distribution of the biopiles in test B.