This short good practice guide looks at what needs to be considered when undertaking a reverse osmosis plant start-up procedure.
The guide reviews both pre-start and start-up procedures for new and existing plant systems.
RO Plant Pre-Start Procedures
Prior to starting a reverse osmosis plant system, it should be verified that all pre-treatment systems are working according to their specifications.
It may be necessary to take water samples for analysis.
In the case of polyamide (thin film composite) membranes free chlorine must be 0.0 ppm.
The Silt Density Index (SDI) should be according to the RO design guidelines (typically < 5.0).
If the water analysis, including temperature, pH etc. has changed significantly, it is recommended that you run a new scale projection analysis on Accepta’s automated RO software calculator.
RO Systems - Good Practice Guide
On start up, the inlet valve should open prior to the initiation of the high-pressure pump, to completely fill the system with low pressure water (<100 psi [< 7 Bars]).
This “soft start” will prevent hydraulic shock at start-up.
Pre-treatment chemical addition should begin at this time (making sure the chemicals are not over-injected).
The high-pressure pump should then be started and the system slowly bought on-line, up to design permeate flow.
If starting up after a period of shutdown, flush the permeate to drain for 30 minutes to remove residual preservation chemicals.
Produced water permeate can be used when it meets the quality requirement of downstream processes.