**5. Materials and research preparation**

#### **5.1 Sampling**

The study has been carried out on microbial colonies of sludges collected in sterile bottles from Acerra (Italy) mixed industrial-civil wastewater treatment plant *Experimental Investigation of Biomass Attachment to Wastewater Reactors DOI: http://dx.doi.org/10.5772/intechopen.94426*

and from CoDiSo tannery wastewater treatment plant of Solofra (Italy), subject and not subject to a physical–chemical process. More precisely, the overall treatment process consists of a sequence of a biological and of a physical–chemical process. Samples have been taken downward of the primary settlement and transported with a thermally insulated bag. After laboratory water removal, the sludges have been distributed into 1.5 ml sterile polystyrene Eppendorf pipettes and 50 ml Falcon tubes. Both have been centrifuged at 10,000 rpm for microbial cell separation and fed with PCB nutrient broth at 20% glycerol. PCB composition has been included in **Table 1**. Settled cells have been suspended in a vortex and stored at 20°C. Wastewater has been collected as well with 4 sterile bottles, notably 2 liters upstream and 2 liters downstream of the physical–chemical treatment unit, with the aim to investigate the toxic and substrate diversity associated with the different sampling points. One fraction of this wastewater has undergone centrifugation, suspension of microbial cells in PCB nutrient broth at 20% glycerol and stored at 20°C. The remaining fraction has been frozen for further tests.
