## 3 Results and Discussion
### Operational Aspects and Judement of the Plant Managers
#### 3.2.1 Characteristics of the MBR Plants Analyzed  
Regarding the treatment train, all municipal MBR plants include coarse screening, fine screening, grid and fat removal, denitrification, oxidation-nitrification, and membrane filtration. The effluent is always discharged in water bodies; the effluent of six plants is internally reused, as well. The treatment trains of the industrial MBR plants are very different as well as the effluent destination (Table 3).  
As concerns the type of membrane, the 67% of MBR plants investigated in the second part of the survey, both for municipal and industrial wastewater treatment, uses hollow-fiber membranes; in the other plants, flat-sheet membranes are adopted. A total of 80% of the municipal MBR plants adopt sodium hypochlorite and citric acid for membrane cleaning, whereas about 20% use sodium hypochlorite only. In few industrial MBR plants, sulphuric and hydrochloric acids are used as well.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Industrial** & **Treatment Train 1 ** & **Effluent Destination** \\ \hline \#1 & Flot \(\rightarrow\) Coag/Flocc \(\rightarrow\) Nit \(\rightarrow\) Den \(\rightarrow\) MF & Water body \\ \#2 & FS (1.5 mm) \(\rightarrow\) Equal \(\rightarrow\) Den \(\rightarrow\) Nit \(\rightarrow\) MF & Water body \\ \#3 & FS (3 mm) \(\rightarrow\) Neutral \(\rightarrow\) Bio \(\propto\) MF & Water body \\ \#4 & FS (1 mm) \(\rightarrow\) Equal \(\rightarrow\) Flot \(\rightarrow\) Bio \(\propto\) MF & Water body \\ \#5 & FS \(\rightarrow\) Equal \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Sewer \\ \#6 & FS (1.5 mm) \(\rightarrow\) Flot \(\rightarrow\) Equal \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Water body/reuse \\ \#7 & FS \(\rightarrow\) G/F rem \(\rightarrow\) Den \(\rightarrow\) Nit \(\rightarrow\) MF & Water body \\ \#8 & FS (1 mm) \(\rightarrow\) Equal \(\rightarrow\) Neutr \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Sewer \\ \#9 & FS (1 mm) \(\rightarrow\) Equal \(\rightarrow\) Neutr \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Water body/reuse \\ \#10 & FS (1 mm) \(\rightarrow\) Equal \(\rightarrow\) Neutr \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Water body/reuse \\ \#11 & FS (3 mm) \(\rightarrow\) Equal \(\rightarrow\) Neutr \(\rightarrow\) Flot \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Water body/reuse \\ \#12 & FS (1 mm) \(\rightarrow\) Equal \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Soil/subsoil \\ \#13 & FS (1 mm) \(\rightarrow\) G/F rem \(\rightarrow\) Equal \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Soil/subsoil \\ \#14 & FS (1 mm) \(\rightarrow\) G/F rem \(\rightarrow\) Den \(\rightarrow\) Nit \(\rightarrow\) P rem \(\rightarrow\) MF & Soil/subsoil \\ \#15 & Equal \(\rightarrow\) Neutr \(\rightarrow\) Flot \(\rightarrow\) Nit \(\rightarrow\) Den \(\rightarrow\) MF & Water body \\ \#16 & FS (2 mm) \(\rightarrow\) Equal \(\rightarrow\) Flot \(\rightarrow\) Den \(\rightarrow\) Nit \(\rightarrow\) MF & Sewer \\ \#17 & Neutr \(\rightarrow\) Flot \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Water body \\ \#18 & CS \(\rightarrow\) FS \(\rightarrow\) Flot \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Water body \\ \#19 & Equal \(\rightarrow\) FS(1 mm) \(\rightarrow\) Den \(\rightarrow\) Nit \(\rightarrow\) MF & Water body \\ \#20 & FS (2 mm) \(\rightarrow\) Sed \(\rightarrow\) Nit/Den \(\rightarrow\) MF & Sewer \\ \#21 & Equal \(\rightarrow\) Coag/Flocc \(\rightarrow\) Sed \(\rightarrow\) Bio \(\propto\)\(\rightarrow\) MF & Sewer \\ \hline \hline \end{tabular}
\end{table}
Table 3: Treatment train and effluent destination of the industrial MBR plants.  
Figure 4: Classification of the MBR plants investigated in the second step of the survey.