System OperationIntroductionSuccessful long-term performance of the RO system depends on proper operation andmaintenance of the system.Preventing, fouling or scaling of the membrane is not only a matter of system design, but also amatter of proper operation.Record keeping and data normalization is required in order to know the actual plant performanceand to enable corrective measures when necessary.Initial Start-UpThe initial system start-up is typically performed just after the element loading. The material neededfor initial start-up is as under. Safety glasses when working with chemicals. Thermometer, pH meter & conductivity meter (range from permeate to brine conductivity). 3 or 4 clean plastic bottles for sampling purpose. analysis equipment for- Total hardness, calcium, alkalinity, chloride, sulfate, iron, silica, free chloride etc.
Pre Start-Up Check• Ensure pretreatment is okay.• Ensure the absence of chlorine, turbidity, grease, oil, & any type of oxidizing agent.• Ensure that the SDI must be less than 3.• The raw water intake must be stable with respect to• Flow, SDI, turbidity, temperature, pH, conductivity, bacteria,• Ensure pretreatment is okay.• All piing and equipments compatible with designed pressure.• All piping and equipment is compatible with designed pH range (clenaing).• Media filters are backwashed and rinsed• New/clean cartridge filter is installed directly upstream of the high pressure pump• Feed line, including RO feed manifold, is purged and flushed, before pressure vessels areconnected.• Chemical addition points are properly located.• Check valves are properly installed in chemical addition lines• Provisions exist for preventing the RO system from operating when the dosage pumps are shutdown
Pre Start-Up Check• If chlorine is used, provisions exist to ensure complete chlorine removal prior to the membranes.• Planned instrumentation is installed.• Instrumentation is calibrated.• Pressure switch protection is installed and correctly set.• Provisions exist for preventing the product pressure from exceeding the feed/brine pressure morethan 0.3bar (5 PSI) at any time.• Interlocks, time delay relays and alarms are properly set.• Provisions exist for sampling permeate from individual modules.• Provisions exist for sampling feed, permeate and reject streams from each array and the totalplant permeate stream.• Pressure vessels are properly piped both for operation and cleaning mode• Pressure vessels are secured to the rack or frame• Pumps are ready for operation• Fittings are tight & permeate line is open• Reject flow control valve is in open position.
Typical Start-Up Sequence:• Before initiating the start-up sequence, thoroughly rinse the pretreatment section to flush out debris and othercontaminants without letting the feed enter the elements. Follow the pre-start-up check.• Check all valves to ensure that settings are correct. The feed pressure control and concentrate control valvesshould be fully open.• Use low pressure water at a low flow rate to flush the air out of the elements and pressure vessels. Flush at agauge pressure of 30 to 60 psi.• During the flushing operation, check all pipe connections and valves for leaks.• After the system has been flushed for a minimum of 30 minutes, close the feed pressure control valve. Ensurethat the concentrate control valve is open.• Slowly crack open the feed pressure control valve (feed pressure should be <60 psi).• Start the high pressure pump.• Slowly open the feed pressure control valve, increasing the feed pressure and feed flow rate to the membraneelements untill the design concentrate flow is reached. Continue to send all permeate and concentrate flows to anapproved waste collection drain.• Slowly close the BCV until the ratio of permeate flow to concentrate flow approaches.• Continue to check the system pressure to ensure that it does not exit the upper design limit
• Typical Start-Up Sequence:• Repeat last two steps until the design parameters are obtained.• Check chemical addition of all the dosing system as per design.• Measure feed water pH.• Check LSI and ensure it is under limit.• Allow the system to run for one hour.• Take the first reading of all operating parameters.• Read the permeate conductivity from each pressure vessel & identify any vessel that do notconfirm to performance expectations.• After 24-48 hours operation read all plant performance data such feed pressure, differentialpressure, flow, recovery, pH & conductivity readings.• Compare system performance to design value.• Confirm proper operation of mechanical & instrumentation safety devices.• Switch the permeate flow from drain to normal operation position.•Remarks: It is important to refer Rosa run out & Argo run out during typical start up of the systemfor confirmation of system performance.
• Typical Start-Up Sequence:• Repeat last two steps until the design parameters are obtained.• Check chemical addition of all the dosing system as per design.• Measure feedwater pH.• Check LSI and ensure it is under limit.• Allow the system to run for one hour.• Take the first reading of all operating parameters.• Read the permeate conductivity from each pressure vessel & identify any vessel that do notconfirm to performance expectations.• After 24-48 hours operation read all plant performance data such feed pressure, differentialpressure, flow, recovery, pH & conductivity readings.• Compare system performance to design value.• Confirm proper operation of mechanical & instrumentation safety devices.• Switch the permeate flow from drain to normal operation position.•Remarks: It is important to refer Rosa run out & Argo run out during typical start up of the systemfor confirmation of system performance.
Normal Shut Down• After flushing the system, the feed valve(s) is (are) closed completely.• When the system has to be shutdown for extended period of time longer than48 hours, take care that-The element do not dry out- The system is adequately protected against microbiological growth or regularflushing is carried out every 24 hours.- When applicable the system is protected against temperature• If feed water for flushing every 24 hrs is not available, preservation withchemical is necessary for longer stop than 48 hours.
RECORD KEEPINGIn order to be able to follow the plant performance of the RO unit, it is necessary that all relevantdata are collected, recorded and kept on file. This is valuable tools for trouble shooting and areneeded in case of warranty claims.Start Up Report:Provide a complete description of RO plantGive results of checking according to check list.Record initial performance of RO & Pretreatment system.RO Operating Data:Date, time & hours of operationPressure drop per cartridge and per array.Feed, permeate and concentrate pressure of each array.Permeate and concentrate flow of each array.Conductivity & pH of feed, permeate and concentrate.SDI of RO feed.Complete water analysis of the feed, permeate & concentrate.
3. Pre-treatment Operating DataTypically the following items must be recorded.• Total residual chlorine concentration in the RO feed.• Discharge pressure of any well or booster pumps.• Pressure drop of all filters & consumption of all dosing chemicals.• Caliberation of all instruments & any unusual incident.4. Maintenance log• Record routine maintenance.• Record mechanical failure & replacement• Record any change of any membrane location with serial number.• Record replacement or addition of RO device & pretreatment.• Record caliberation of all instruments.• Record all cleaning of RO membranes include date, duration of cleaning, cleaning agent &concentration, solution pH, temperature during cleaning, flow rate & pressure.
Control of Microbiological ActivityBio fouling is one of the most common & most severe problems in the operation of ROsystem. Especially for plant using surface water or bacteriologically. Adequatesampling point should be provided to make a microbiological balance & control in theplant.• Intank (surface) or well before chlorination if any.• After a clarifier, settling pond, sludge contact units or similar sedimentationprocess.• After filtration unit (PSF, ACF etc).• Concentrate stream and permeate stream.The frequency of sampling & analysis depends on the risk of Biofouling.
DO’S & DON’T GUIDE LINESDO’s-Follow the guide lines provided in O&M Manual for proper starting and shut down.- Carry out minimum 15 min. flushing before starting and shutdown of the plant.- The plant to be operated by the trained and experienced personnel in Reverse Osmosis.- Check the SDI of the feed water every day and maintain the filter papers for record.- Check the pressure difference of the MCF and closely monitor the same.- check all Permionics system is working as per requirement.- To change the MCF cartridge if the pressure difference exceeds more than 0.8 kg/cm2 OR once in threemonths whichever earlier.- Before starting HPP, keep the system full of water and free of air.- Check for any abnormality of HPP, if found, stop the plant.- Monitor the system pressure at different level of the process as per the recommendation provided in the O&Mmanual.- Correctly balance the RO product and reject flow rate as per the plant design and specifications.- Ensure system interlocks are inline as a protection to the plant equipments.
• DO’S & DON’T GUIDE LINES•DO’s•Observe the press, difference across the RO Module & quality of product water.• Calibrate at regular intervals as per our recommendation all the instruments for accuracy,reliability of dates for ensuring overall integrity and efficiency of the plant.• Keep proper record keeping such as daily operational logsheets review the plant status, recordingof daily events, activities carried out and to maintain the equipment history record to carry outnecessary service intime.• Always maintain minimum inventory of original spares and regular consumables to reduce downtime of the plant equipments.
DO’S & DON’T GUIDE LINESDON’T•Operate the plant when the SDI of the feed water is more than the limiting factor specified.• Operate the plant when the pressure difference across MCF is more than 1.0 kg/cm2.• Operate the plant when the feed water conductivity is more than the limiting factor specified.• Operate the HPP with LSS by passed and with specified value (80% of feed flow)•Open the RO module incase of any deviations of the plant parameters without prior information toduring the guarantee period.• Operate the plant without checking the presence of any oxidizing agents such as ozone, chlorinein the RO feed.• Use duplicate spare parts / regular consumables which may impair the long life of system andequipments.
“Water when you want, as you want” “When you stop communication, you’ve lost your benefits.” JAY WATER MANAGEMENT PVT. LTD. Ashok J Thakkar Manager (Marketing)