3.4. Comparison of energy consumption
As described previously, the dead-end filtration mode
had the higher flux but the shorter backwashing interval
than the crossflow mode. As an alternative criteria for
selecting the better MF mode, the energy supplied to
the pump and compressor to produce the unit volume of
permeate was evaluated according to the MF mode and
crossflow rate.
From the basic Newton’s law, the power (Pp) that
pushes the incompressible fluid from the pump can be
expressed by multiplying the feeding flow rate (v) by the
pressure drop (DP), because water can be considered as
an incompressible fluid. In this study, the feeding flow
rate and the trans-membrane pressure changed as the flux
declined and thus the power changed with the operation
time. Therefore, the energy used can be obtained by integrating
the power with respect to time and the amount