The document outlines a typical start-up sequence for a reverse osmosis system with the following key steps: 1. Thoroughly rinse the system before start-up to flush out debris. 2. Check valves and settings, and flush the system with low pressure water to remove air from the elements and vessels. 3. Gradually increase the feed pressure and flow rate until the design concentrate flow is reached, keeping the pressure increase below 10 psi per second for a soft start.

1. Typical Start-Up Sequence
a. Before initiatingthe start-upsequence,thoroughlyrinse the pretreatmentsectiontoflushoutdebrisandother
contaminantswithoutlettingthe feedenterthe elements.Followthe Pre-Start-upcheckdescribedinPre-Start-up
Checkand CommissioningAudit(Section5.2.2).
b. Checkall valvestoensure thatsettingsare correct.The feedpressure control andconcentrate control valves
shouldbe fullyopen.
C. Use lowpressure waterata lowflowrate toflushthe air out of the elementsandpressure vessels. Flushata
gauge pressure of 30 to 60 psi (0.2 - 0.4 MPa/2.07-4.13 bar).All permeate andconcentrate flowsshouldbe
directedtoan appropriate waste collectiondrainduringflushing
D. Duringthe flushingoperation,checkall pipe connectionsandvalvesforleaks.Tightenconnectionswhere
necessary.
E. Afterthe systemhasbeenflushedforaminimumof 30 minutes,close the feedpressure control valve.
F. Ensure that the concentrate control valve isopen.
Startingagainsta closedor almostclosedconcentrate valve couldcause the recoverytobe exceededwhichmay
leadto scaling.

2. G. Slowlycrackopenthe feedpressure control valve (feedpressureshouldbe lessthan60 psi/0.4 MPa/4.13 bar).
H. Start the highpressure pump
I. Slowlyopenthe feedpressure control valve,increasingthe feedpressure andfeedflow rate tothe membrane
elementsuntil the designconcentrate flow isreached.The feedpressure increase tothe elementsshouldbe less
than 10 psi (0.07 MPa/0.69 bar) persecondto achieve asoftstart. Continue tosendall permeate andconcentrate
flowstoan appropriate waste collectiondrain.
If the feedpressure and/orthe feedflowrate are rampeduptoo quickly,the housingof the elementsmaybe
damagedbyexcessive forcesinflowdirectionand/orinradial direction - especiallyif airisinthe system - leading
to telescopingand/orfiberglassshell cracking
J. Slowlyclose the concentrate control valveuntil the ratioof permeate flow toconcentrate flow approaches, but
doesnotexceed,the designratio(recovery).Continue tocheckthe systempressure toensure thatitdoesnot
exceedthe upperdesignlimit.
K. Repeatsteps"i"and"j" until the designpermeateandconcentrate flowsare obtained.
L. Calculate the systemrecoveryandcompare itto the system'sdesignvalue.
M. Checkthe additionof pretreatmentchemicals(acid,scale inhibitorandsodiummetabisulfiteif used).Measure
feedwaterpH.
N. Checkthe LangelierSaturationIndex (LSI)orthe Stiff &Davis StabilityIndex (S&DSI)of the concentrate by
measuringpH,conductivity,calciumhardness,andalkalinitylevelsandthenmakingthe necessarycalculations.
O. Allowthe systemtorunfor one hour.
P. Take the firstreadingof all operatingparameters.
Q. Checkthe permeate conductivityfromeachpressure vessel toverifythatall vesselsconformtoperformance
expectations(e.g.,vesselswithleakingo-ringsorotherevidence of malfunctiontobe identifiedforcorrective
action).
R. After24 to 48 hoursof operation,reviewall recordedplantoperatingdatasuchas feedpressure,differential
pressure,temperature,flows,recoveryandconductivityreadings(please refertoRecordKeeping,Section5.6).At
the same time draw samplesof feedwater,concentrate andpermeate foranalysisof constituents.
S. Compare systemperformance todesignvalues.
T. Confirmproperoperationof mechanical andinstrumentalsafetydevices.
U. Switchthe permeate flowfromdraintothe normal service position.
V. Lock the systemintoautomaticoperation.
W.Use the initial systemperformance informationobtainedinsteps"p"through"r"as a