8/7/2019 0901b80380391a39

1/4

Food & Dairy Product Bulletin

DOW Reverse Osmosis MembranesQuick Reference Guide Reverse Osmosis

What is reverse osmosis?

Reverse osmosis (RO) is the finestlevel of filtration currently available.RO is a pressure-driven membraneprocess that separates purified waterfrom a feed stream. RO is so-calledbecause it is the opposite of thenatural process known as osmosis.

What is the DOWFILMTEC FT30membrane?

FT30 is a thin-film composite, semi-permeable membrane with a poresize in the angstrom range. FT30exhibits high water throughput, orflux, while acting as a barrier todissolved salts and organic materials.Typical solute rejections are listed inT a b l e 1 . T h i n - f i l m c o m p o s i t edescribes the multi-componentcompos i t ion o f the membrane,allowing optimization of each layer.

Why use DOW ROmembranes?

Dow has offered leading reverseosmosis technology for more than 20years. DOW FILMTEC FT30membrane chemistry is globallyrecognized as state-of-the-art.

Dow food processing elements havebeen optimized to offer increased activemembrane area on a consistent basisthrough automated glueline placementand element fabrication. DOW elementsare designed for, and used in, a widerange of applications, from processstreams to water purification. Our goalis to offer customers the best value inmembranes through performance andcustomer support. Dow reverse osmosisproducts for food and dairy are listed inTable 2.

Some specific application examples for DOWFILMTEC ROelements include:

Product concentration

Evaporator condensate polishing

RO permeate polishing

Water recovery/reuse

Energy recovery

Pretreatment of plant or process make-up water

Wastewater treatment

Water removal prior to evaporation; pre-concentration

UF/MF permeate processing

Do Dow membranes meetgovernment standards?

Dow elements designed for food anddairy applications are based on theneeds of food and dairy processors. Allcomponents of Dow food processingelements are compliant with U.S. Foodand Drug Administration indirect foodcontact guidelines.

Table 1 - Solute Rejection (Approximate)

Solute MW Rejection Solute MW Rejection

Sodium chloride 58 99% Ethanol 46 70%

Sodium nitrate 85 93% Isopropanol 60 90%

Magnesium chloride 95 99% Lactic acid (pH 2) 90 94%

Calcium chloride 111 99+% Lactic acid (pH 5) 90 99%

Magnesium sulfate 120 99+% Lactose 342 99+%Dissolved reactive silica 60 98% Sucrose 342 99+%

2000 ppm Solute, 225 psi (15 bar), 77F (25C), pH 7.0, 15% recovery (unless otherwise noted)

8/7/2019 0901b80380391a39

2/4

Examples of Conditions Where Membrane Systems Could be EconomicallyAdvantageous

1. Evaporator Limitations Figure 1 Pre-concentration and Polishing of a Process Stream

, or

fy a plants fresh

Reverse osmosis technology iswidely used by processors who

require increased capacity without thepurchase of a new evaporator. ROpre-concentrates a stream byremoving water, allowing more solidsto be processed. Scenarios forpre-concentration with RO are found inFigures 1 and 3.

By pre-concentrating a stream by 2-4times, an RO system results in lessload on the downstream evaporator.It allows a plant to process additionalproduct with minimal capitalinvestment.

2. Wastewater Recovery/Reuse

Water going down the drain not onlyleads to disposal costs, it is a lostresource. Membrane systems canoften treat wastewater streams tominimize disposal costs and torecover water for reuse. In somecases, the concentrated wastestream also becomes a saleableproduct.

Reverse osmosis is generally the finaloperation of a treatment process thatoften includes other membrane types.

3. Evaporator CondensateStream

Evaporator condensate polishing hasbecome a very common reverseosmosis application during the pastseveral years. Polishing condensatethrough RO offers a source of cleanwater tha t may be reused. Theenergy from this stream may also berecovered through heat exchange.

RO membranes typically reduce the

BOD content of condensate streamsto less than 10 ppm. Similarly, anRO polishing system is often used tofurther reduce BOD from an ROprocess stream.Examples of polishing systems areillustrated in Figures 1 and 2.

4. Treatment of Process Water

Reverse osmosis is often used topurify the water being used in anentire plant or for a specific process.Improved water quality can have apositive effect on finished productquality and consistency. It can also

ensure consistency for productsprocessed in different locations.

Downstream treatment concernssuch as silica, hardness, scalemineral content can often beaddressed more economically byusing RO to purimake-up water.

RO Retentate(ConcentratedDissolved Solids)

RecombinedRetentatesPre-concentrated Juice20 Brix

8/7/2019 0901b80380391a39

3/4

Figure 2 Evaporator Condensate Polishing Figure 3 Reverse Osmosis of Whole WheyFigure 2 Evaporator Condensate Polishing Figure 3 Reverse Osmosis of Whole Whey

FeedCow WaterCond. = 5 mho/cm

BOD = 100 ppmRate = 100 gpm

T = 110 F

Permeate

Polished Water

Cond. = 1 mho/cmBOD < 10 ppm

Rate = 90 gpm

Retentate

Water

Cond. = 50 mho/cmBOD < 1000 ppm

Rate = 10 gpm

RO System

Recycle /

ReuseDisposal

FeedWhole Whey(Clarified & Defatted)6.5 wt% total solids

0.6 wt% protein

4.8 wt% lactose

PermeateWater

0.15 wt% total solids0.04 wt% protein

0.09 wt% lactose

RetentateConcentrated Whey20.0 wt% total solids

3.2 wt% protein15.3 wt% lactose

RO System

Disposal Evaporator

Table 2 DOW Reverse Osmosis Products for Food & Dairy ApplicationsTable 2 DOW Reverse Osmosis Products for Food & Dairy Applications

ProductProduct Part numberPart number Design active area ft2 (m2)Design active area ft2 (m2) Outer CasingOuter Casing

DOW Food and Dairy RO-8038DOW Food and Dairy RO-8038 302219 / (302218)302219 / (302218) 370 (34.4)370 (34.4) Outer shellOuter shell

DOW RO-390-FF 116314 / (100608) 390 (36.2) Mesh wrap

DOW RO-3840 / 30-FF 196310 / (108664) 81 (7.5) Mesh wrap

DOW RO-3838 / 30-FF 80588 / (80589) 79 (7.4) Mesh wrap

DOW RO-3938 / 30-FF (117259) 85 (7.8) Mesh wrap

Part numbers in brackets are wet elements.

Note: 3838 and 3840 elements are designed for use in 14-gauge sanitary tubing.

8040 elements are designed for use in Schedule 40 pressure vessels.

8/7/2019 0901b80380391a39

4/4