**6.3 Microbial growth and development of biofilm in industrial wastewater**

Activated sludges collected from Acerra treatment plant have been adopted as microbial matrix, whereas treated and untreated wastewaters coming from Solofra treatment plant (**Table 8**) have been used as substrate. Count of suspended bacteria instead of spectrophotometry was due to the significant TDS and to the related difficulty to calibrate the instrument. Having the count been carried out at irregular intervals during the test, it was not possible to draw a growth curve, but, based on the final bacterial load, it was possible to estimate the growth trend and the

**Figure 5.** *Effects of substrate of microbial growth with nitrogen-compounds.*

*Experimental Investigation of Biomass Attachment to Wastewater Reactors DOI: http://dx.doi.org/10.5772/intechopen.94426*

**Figure 6.**

*Tannery wastewater treatment – Quality of the effluent.*


#### **Table 8.**

*Untreated wastewater characteristics.*

survivability of the microbial matrix. Findings of bacterial count are shown in **Table 9**. A longer survivability was observed in wastewaters which underwent chemical settlement and flocculation, as expected from the very high toxic load of tannery effluents. Quality of the effluent in terms of foam formation, clarification and presence of filaments has been shown in **Figure 6** and **Table 10**. Once again, presence or removal of toxic substances are a key driver for the lower or higher degree of clarification. Contrary to the findings of the other tests, which showed same biofilm formation and features, significant even microscopic differences have been identified in this test, as to the attached biomass in the various substrates. A qualitative relative indication of the biomass formation has been shown in **Figure 7**. The layer observed at the microscope even at high toxic concentrations can be


#### **Table 9.**

*Tannery wastewater. Bacterial count after 24 hours at different dilutions.*


#### **Table 10.**

*Quality of treatment of tannery wastewater.*

**Figure 7.**

*Biofilm formation in tannery wastewater.*

justified by the survival at these concentrations of morphologically different bacterial colonies.
