4.2.4
The listing of water systems then forms the basis of the valueadded
(VA) table, as per Table 2, with one water system per
row. The steps involved in the treatment and preparation
of each of the water systems are then identified and listed
as columns within the table. Variables representing the cost
of that treatment, typically per unit volume, are assigned
within the table where the treatment is relevant to this water
system and left blank where not relevant. In certain cases,
the cost of the treatment is constant across all the water
systems and hence the variable is common, for example
the variable “B”, which represents the cost of the Biological
wastewater treatment plant per unit of water. In other cases
the variable depends on the particular system, for example
“E” which represents the energy consumed by the treatment
and is specific to the treatment applied to the system. The
level of detail applied at this stage is critical, as omission of
any treatments has a significant impact in determining the
accuracy of the entire process. Typically all treatments are
not apparent until illustrated on the PFD and subsequently
outlined in the VA table.