Page 257 - Membranes for Industrial Wastewater Recovery and Re-Use

226 Membranes for Industrial Wastewater ReeoverH and Re-use

The above costs do not include the energy demanded by the backflush process.
Clearly, based on the data given, backflushing cannot not impact significantly on
the total energy demand of the submerged membrane process since it amounts to
only around one-twelfth of the pumping energy demand of the operating cycle,
which itself contributes less than 3% to the total energy demand. Backflushing
does, on the other hand, increase the membrane area requirement due to
downtime, as has been demonstrated above.
These examples demonstrate the general principles of design. As the dispirate
answers from the energy demand calculation by Film Theory (4.3.1) and RO
CAD (4.3.3) suggest, basic assumptions made about fundamental properties of
the system can profoundly influence the answer obtained. Accurate information
on performance, both hydraulic and water purification, demands pilot trials
and/or pertinent data from existing full-scale installations. Such data is given in
Chapter 5.