2.3.1. Optical Density Determination

Prior to the experiments, the waste PUR foams were rinsed with sterilized distilled water in order to remove any undesirable contaminants from their surfaces. The next step was the sonication process, which consisted in immersing each carrier in 0.9% NaCl. The last step in determining the optical density was the measurement of the absorbance of biomass in the tubes with the Spectroquant spectrophotometer at a wavelength of 560 nm (OD₅₆₀). A total of 0.9% NaCl solution was used as a blank.