This White Paper addresses the impact of ERDs on the energy consumption of the RO process using an objective and fully transparent criteria. The analysis shows that published ERD efficiency data has virtually no correlation to the actual energy consumption of the RO system.
There is no standard definition of efficiency for energy recovery devices (ERDs). Each supplier is free to create their own definition that (not surprisingly) often favors their particular technology.
Two new factors are presented, transfer efficiency and field efficiency that allow a more accurate characterization of ERDs in realistic field operation. The impact of various ERDs on energy consumption of a hypothetical 20,000 m3/day SWRO train is presented.
In large scale systems, the analysis clearly indicates turbochargers provide the same or better energy consumption than all other ERDs including Isobaric Chambers.
In particular, isobaric chambers, that purport to have a 97% efficiency have, in fact, an efficiency in range of 83-85% in most field applications. An unfortunate consequence is that efficiency requirements of 95+% are often included in project specifications precluding other ERDs that can offer a significantly lower cost of permeate through comparable energy consumption and reduced CAPEX and OPEX.
It is time to open project specification to all field-proven ERDs and let the market decide the winner
The next generation of desalination will rely on multi-stage, high recovery reverse osmosis, delivering a lower cost of water and improving membrane performance.
Executive Summary Seawater reverse osmosis systems (SWRO) are the mainstay of large-scale desalination systems. Plant designs have settled in a more or less standard configuration using a single membrane stage with permeate recoveries ranging from