3.2. Overall treatment performance
The most common ways to express CW performance are percent
concentration reduction and percent mass removal [6]. In the
present study, the performance comparison of the ten VFCW units
was based on two different approaches: (a) average effluent concentrations
(input–output) and percent removal; and (b) areal load
reduction (ALR). The ALR is the difference between inlet pollutant
loading rate (ILR) and outlet loading rate. It is usually expressed as
the removed pollutant mass per CW surface area and time (g/m2 d),
and represents a useful parameter to assess system efficiency
[6].