3. Results and discussion
3.1. Characteristics of process water
The main internal utilities identified in the WtE plant based on
water usage are showed in Fig. 1, where average flow rates are
reported too, concerning periods when both incineration units
were on. The utility in Fig. 1 named ‘‘Other utilities’’ refers to minor
flow rates, as described above, whose role is negligible from the
point of view of both incineration process and water usage. The
vapour and steam losses are mainly due to the flue gas cleaning
system (80%), and secondarily to the bottom ash quenching
(20%). The specific water consumption of the WtE plant is
1.81 m3 per ton of MSW, which is comparable with literature data.
Starting from the water usages reported in Fig. 1, it was possible
to aggregate the process water flows into two main groups considering
the main pollution issues. In fact, contamination of the various
flows depends on the process in which water is involved: