METITO OVERSEAS LTD.We are committed to total Customer Satisfaction and have developed a documented Quality Management System which ensures that :- Agreed specifications are adhered to.- Relevant National and International Standards are applied.- The materials which we use and companies which we buy from, meet specified requirements.- Every Metito employee does what is expected of him - first time and every time - and concentrates on recognising and meeting his customers needs- Our products and services remain competitive, while offering the best available technology.

Module 5.1

WATER DESALINATION BY REVERSE OSMOSIS

Module 5.1.0 - AGENDAWater QualityOsmosis & Reverse OsmosisPretreatmentR.O. MembranesOperation and Plant ControlTroubleshootingCleaningCost ComparisonsProcess Flow Diagram

Module 5.1.1 Water QualityOVERVIEW

Salt Content of different water sources :Brackish WaterSea WaterDrinking Water Standards

Module 5.1.1 - Water Quality

Low Salinity Water (TDS < 500 mg/l)- Rivers- Springs- Deep WellsBrackish Water (TDS 500 - 16,000 mg/l)Heavy Brackish (TDS 16,000 - 30,000 mg/l)Sea Water (TDS > 30,000 mg/l)

Salt Content

Module 5.1.2 - Osmosis & Reverse Osmosis1. OsmosisOsmosis is a natural occurring process used by many plant & animal tissues to transport liquids across cell walls.

Module 5.1.2 - Osmosis & Reverse Osmosis2. Semi-permeable membrane

Cell walls are examples of semi-permeable membranes which allow water to pass through, while not allowing salts to pass.

Module 5.1.2 - Osmosis & Reverse Osmosis3. Semi Permeable MembraneH2O H2O

Module 5.1.2 - Osmosis & Reverse Osmosis4. Osmosis

Module 5.1.2 - Osmosis & Reverse Osmosis5. Reverse OsmosisPressure

Module 5.1.3.0 - PretreatmentOVERVIEWMajor fouling impuritiesScalingSuspended solids & colloidal matterBiological MatterMetal OxidesSilica

Module 5.1.3 - Pretreatment 1. Major Fouling Components- Sparingly soluble (scale-forming) salts Calcium Carbonate Calcium Sulphate Barium Sulphate Strontium Sulphate Calcium Fluoride- Suspended solids & colloidal matter- Micro-organisms (bacteria & protozoa)- Metal Oxides (e.g. Iron & Aluminium)- Silica

Module 5.1.3 - Pretreatment2. Scale ControlCaused by precipitation of Sparingly Soluble Salts :Calcium Carbonate CaCO3.Calcium Sulphate CaSO4Barium Sulphate BaSO4Strontium Sulphate SrSO4Calcium Flouride CaF4

Scaling Potential Determined by :Chemical Analysis of Feed WaterR.O. System RecoverySolubility Limits of Salts

Module 5.1.3 - Pretreatment3.1 Calcium Carbonate - CaCO3Exists in most waters (as soluble Calcium Bicarbonate, Ca(HCO3)2For Brackish Waters, Scaling potential calculated by Langelier Saturation Index (LSI)For Sea Water / Brine Water the scaling potential is calculated by SDSI

Module 5.1.3 - Pretreatment3.2 Calculating Scale Potential of CaCO3

LSI = pHb - pHsWhereLSI = Langelier Saturation IndexpHb = pH of brine waterpHs = pH of Saturation (I.e. Where CaCO3 will neither deposit nor dissolve)Negative LSI CaCO3 tends to dissolvePositive LSI CaCO3 tends to precipitate

Module 5.1.3 - Pretreatment3.3 Pre-treatments against CaCO3 ScalingAddition of Acid to lower LSIAddition of Anti-scalant to reduce scaling tendency when LSI > 0Softening of Feed using Ion Exchange

Module 5.1.3 - Pretreatment4.1 - Sulphate SaltsIf CaSO4, Ba SO4 or SrSO4 are present in feed water, solubility limits must be calculated.To avoid precipitation IPb must be less than Kspwhere Ipb = the Ion Product of the Brine Water Ksp = the solubility product

Module 5.1.3 - Pretreatment4.2 - Sulphate SaltsIpb=(mCa2+)b(mSO42-)b

IPb > Ksp -Precipitation OccursIPb< Ksp -Solution is unsaturatedIPb = Ksp -Solution saturated(equilibrium)Guideline IPb 0.8 Ksp

Module 5.1.3 - Pretreatment4.3 - Controlling Sulphate Scaling

Reduce Recovery Use Anti-scalants

Module 5.1.3 - Pretreatment5.1 - Suspended Solids & ColloidsSuspended Solids - Removable by SettlingColloids - not removable by settling- Negative charges on surface - stable in water- In R.O. process colloids concentrate at surface of membrane with salts- Leads to colloid de-stabilisation- Colloids coagulate & foul membrane

Module 5.1.3 - Pretreatment5.2 - Measuring Colloid Fouling PotentialUse Silt Density Index (SDI) SDI = [100(1-(ti/tf))] ttWherett = total test time in minutes (usually 15)ti = initial test time in sec. To fill 500 ml sampletf = time in sec. to fill 500 ml sample after 15 min.

Module 5.1.3 - Pretreatment5.3 - Measuring Colloid Fouling Potential

Media Filtration Coagulation / Flocculation (on-line or off-line)

Module 5.1.3 - Pretreatment6.1 - Biological FoulingMost water sources contain microorganismsForm Slime Layer on Membrane SurfaceLeads to rapid pressure drop increase across cartridge filter preceding H.P. PumpSamples from feed & brine must be regularly tested for Total Bacterial Count (TBC).

Module 5.1.3 - Pretreatment6.2 - Controlling Biological FoulingChlorination prior to filtration stageWater must be de-chlorinated prior to reaching membranes.

Module 5.1.3 - Pretreatment7.1 Metal OxidesMost common is iron.Frequently encountered in water in Ferrous (Fe2+) form.In presence of Oxygen, Fe2+ (soluble) oxidized to Fe3+ (insoluble).Aluminium can precipitate as Aluminium Hydroxide.

Module 5.1.3 - Pretreatment7.2 Controlling Metal Oxide Fouling Oxidation Chemical Precipitation

Module 5.1.3 - Pretreatment8.1 - Silica (SiO2)- When super-saturated, soluble silica forms colloidal silica or silica gel on membranes- Control by Reducing recovery Lime Softening pH Control Temperature Control

Module 5.1.4.0 - Membrane TypesOVERVIEWMaterialDesigns

Module 5.1.4 - Membranes Types1. MaterialsCellulose Acetate (Brackish Water)Cellulose Tri-Acetate (Brackish & Sea Water)Polyamide (Brackish & Sea Water)Composite Polyamide TFCL (Brackish & Sea Water)

Module 5.1.4 - Membranes Types2.1 Plate & Frame Design

Module 5.1.4 - Membranes Types2.2 Tubular Design

Module 5.1.4 - Membranes Types2.3 Spiral Wound Design

Module 5.1.4 - Membrane Types2.4 Hollow Fibre Design[B-10 Single Bundle Permeator]

Module 5.1.4 - Membrane Types2.5 Hollow Fibre DesignB-10 Twin Permeator

Module 5.1.5.0 - Operation & Plant ControlOVERVIEWBasic EquationsWater QualityPressuresRecoveryChemical Addition

Module 5.1.5 - Operation & Plant Control1.1 Basic EquationsQw = Kw (A/t)(P - ) TMwhereQw= flow rate through membraneKw = permeability coefficientA = membrane surface areat = membrane thicknessP = differential pressure across membraneII = osmotic pressure differentialT = temperature effectM = membrane flux decline effect

Module - Operation & Plant Control1.2 Basic EquationsQf = Qp + QbWhere : Qf = feed flow rate Qp = permeate flow rate Qb = brine flow rate (reject)

Module 5.1.5 - Operation & Plant Control1.3 Basic EquationsY = Qp/ QfWhere Y=recovery (conversions) Qp = permeate flow rate Qf = feed flow rate.

Module 5.1.5 - Operation & Plant Control1.4 Basic Equations

WhereCF=concentration factorQb = brine flow rate (reject)Qf= feed flow rate

CF = Qf/ Qb

Module 5.1.5- Operation & Plant Control1.5 Basic Equations

CF = 1 / (1 - Y)Where CF=concentration factor Y=recovery (conversions)Brine chemical composition can be estimated using this equation

Module 5.1.5 - Operation & Plant Control2.1 Water QualityCheck that .. Chlorine in feed is zero Iron in feed is less than 0.05 mg/l SDI of feed water is less than 3 TDS of feed water is within R.O. Design Criteria

Module 5.1.5- Operation & Plant Control3.1 PressuresCheckPump discharge pressureSystem pressure (1st Stage)Intermediate pressureReject (Brine) pressurePermeate pressure

Module 5.1.5- Operation & Plant Control

Feed WaterPermeateBrine

Module 5.1.5 - Operation & Plant Control3.2 Why pressure is important?Assures plant is running according to design pressure.Allows normalization of plant operation to evaluate performance.Indicates fouling when pressure changes significantly under steady operating conditions.

Module 5.1.5 - Operation & Plant Control4.1 RecoveryRatio of permeate flow to total feed flowY = Qp/Qf

Module 5.1.5 - Operation & Plant Control4.2 Important to operate at Design Recovery in order to :Prevent over-saturation of sparingly soluble salts.Not exceed hydraulic guidelines of membranes, e.g. min. & max. brine rates, flux, etc.Produce required permeate quality.

Module 5.1.5 - Operation & Plant Control 5. Chemical AdditionDosing Sets includeCoagulant to reduce colloidal fouling.Acid dosing for pH adjustment to reduce scaling potential.Chlorine dosing to control microbiological growth.De-chlorination agent to remove free chlorine prior to membranes.Antiscalant dosing.Alkali dosing to adjust permeate water pH to required level.

Module 5.1.6 - Troubleshooting1. Troubleshooting TechniquesMost problems related to fouling :IndicatorsPermeate QualityPermeate QuantitySalt RejectionPressure DifferentialAccurate operation log is critical for successful troubleshooting

Module 5.1.6 - Troubleshooting2. On-line InvestigationsPerformed while system in operationMeasure the following :Salt RejectionProduct flowPressures (feed, interstagem reject)

Every permeator has to be checked.

Module 5.1.6 - Troubleshooting3. Off-line InvestigationsPermeators removed from service.Individual elements identified.

Module 5.1.7 - Cleaning1. Why Clean ?Frequent cleaning is not required for properly designed and operated R.O. systems.

Module 5.1.7 - Cleaning2. When to cleanProductivity reduced by 10 - 20%Salt passage increased by 1.5XBundle pressure drop P > 60psi

Module 5.1.7 - Cleaning3. How to Clean Cleaning should be performed after R.O. data has been normalised. Changes observed not due to changes in operating conditions. If bacteriological tests show bacteria in permeate then biocide cleaning is required.

Module - Cleaning4. Different Cleaning ChemicalsDetergent to remove colloidal foulants.Citric acid to remove iron oxide.Formaldehyde for biological control.

REVERSE OSMOSISIMPORTANCE OF FLUSHINGCorrosion rates of stainless steel elements in stagnant water are very high.Antiscalant, if used, produces a metastable state with respect to precipitation of sparingly soluble salts.Upon shutdown, precipitation can occur within four hours if the permeators are not flushed.

REVERSE OSMOSISIMPORTANCE OF FLUSHINGUpon shutdown, reverse osmosis process will cease and natural osmosis will occur.Water flows from the fibre bore to the fibre feed-brine side.If an adequate volume of permeate water at positive pressure (draw-back tank) is not supplied, fibre dehydration will occur.

Module 5.1.7 - Cleaning5. Cleaning Equipment

Module 5.1.8 - Cost Comparisons1. Permeator Replacement Rates

Plant Capacity Startup Average% m3/day Date Replacement Rate/year

Module 5.1.8 - Cost Comparisons2. Cost Comparison R.O. vs. Distillation Capital and Total Water Cost

5.1.8. - Cost Comparisons3.1 Reasons for R.O. Economic Advantages

R.O. Plant requires 1/4 - 1/2 energy required by thermal processes

Module 5.1.8 - Cost Comparisons3.6 Reasons for R.O. Economic AdvantagesModular approach of modern R.O. Plant eliminates the need to shut down the entire plant for scheduled or emergency maintenance

Module 5.1.8 - Cost Comparisons3.3 Reasons for R.O. Economic AdvantagesPrices of non-ferrous metals used in thermal processes have increased 50 - 100% in the last 10 yearsMembrane prices, however, have remained fairly constant

Module 5.1.8 - Cost Comparison3.4 Reasons for R.O. Economic AdvantagesMaterials of construction used throughout thermal plants are more costly than in R.O. plants, because of the higher operating temperatures.

Module 5.1.8 - Cost Comparisons3.5 Reasons for R.O. Economic AdvantagesExtensive operator training required for thermal processes, but not for R.O. Plant.

Module 5.1.8 - Cost Comparisons3.6 Reasons for R.O. Economic AdvantagesModular approach of modern R.O. Plant eliminates the need to shut down the entire plant for scheduled or emergency maintenance.

Module - Cost Comparisons3.7 Reasons for R.O. Economic AdvantagesR.O. Plants require only half the space needed to the thermal desalting systems.

Module - Cost Comparisons3.8 Reasons for R.O. Economic AdvantagesR.O. plants require around 1/3 of the seawater feed necessary for MSF and MED systems.Intake and pre-treatments systems are smallerEnvironmental impact more acceptable.Intake and pre-treatments systems are smaller.

Module 5.1.9 - Process Flow DiagramSea Water R.O. Plant - KFNB

Module 5.1.9 - Process Flow DiagramSea Water R.O. Plant - KAIA