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Filtration Applications

Reverse Osmosis

Milk

Whole Milk

Preconcentration Ahead of Cheese Production

Whole milk can be concentrated with Reverse Osmosis (RO) to levels of 25-30% total solids (TS). This represents a 2-2.5x volume concentration factor (VCF).

RO refers to a pressure driven membrane separation technique in which a membrane is employed to separate different components in a fluid mixture. RO membranes have pore sizes less than 0.001 micron. Separation occurs based on molecular size and chemical interactions between the membrane and fluid components that are in contact with the membrane. In this process, pressure is used to push water molecules through the pores of a membrane while retaining the colloidal solids and salts. Typical operating pressures range from 450-600 psi.

Permeate quality from RO systems depends on the quality and composition of the feed and the level of concentration. The higher the TS, the greater the amount of constituents in the permeate. Typically, RO permeate will contain small (but measurable) amounts of organic solids. The process performance is greatly affected by operating parameters such as feed flow rate, pressure, temperature, pH, micro-biological quality of feed stream, feed concentration, and fouling characteristics of the membrane for various components.

Reverse Osmosis, which avoids the phase change seen with evaporation, preserves the functionality of proteins and the product does not have a cooked flavor. Processing temperature of whole milk is typically ~45°F. Systems are properly designed and operated to maintain the integrity of the fat molecules. Doing so prevents the rancidity caused by damaged or ruptured fat molecules.

Filtration Applications

Skim Milk

Buttermilk concentration by cold reverse osmosis (RO) is frequently used as an efficient and economical way to increase capacity of a skim milk evaporation operation. MSS' cold milk experience has shown it technically feasible to pre-concentrate raw cold (45°F) whole milk without fat damage, excessive fouling, or any rancidity. By locating the cold RO ahead of the existing HTST/separator, the existing equipment does not need to be revised. Up to 25% increase in plant capacity can be achieved with the addition of a cold whole milk RO without increasing separator or pasteurizer capacity. Although the cost for a cold whole milk RO is somewhat higher that a warm skim RO, the savings by not increasing the pasteurizer and not adding to the separation capacity results in an overall lower investment. Generally, membranes operated colder at lower concentration last longer. The cold RO permeate can effectively be utilized for cream pre-cooling or other energy saving applications.

Permeate quality from RO systems depends on the quality and composition of the feed and the level of concentration. The higher the TS, the greater the amount of constituents in the permeate. Typically, RO permeate will contain small (but measurable) amounts of organic solids. The process performance is greatly affected by operating parameters such as feed flow rate, pressure, temperature, pH and micro-biological quality of feed stream, feed concentration and fouling characteristics of the membrane for various components.

Reverse Osmosis, which avoids the phase change seen with evaporation, preserves the functionality of proteins and the product does not have a cooked flavor. Processing temperatures of skim milk are typically < 45°F or ~120°F. Skim milk can be concentrated for several reasons: reduced volume for transportation, increased production capacities, or increased TS for use in fortification. Cream skimmed from the milk prior to concentration with RO can be added to the concentrated skim in order to obtain "concentrated whole milk".

Filtration Applications


Whey

Sweet/Acid Whey

Whey concentration by reverse osmosis (RO) is frequently used to reduce volumes and increase solids content prior to transportation or further processing. RO refers to a pressure-driven membrane separation technique in which a membrane is employed to separate different components in a fluid mixture. A Reverse Osmosis membrane has pore sizes less than 0.001 micron and separation occurs based on molecular size and chemical interactions between the membrane and fluid components that are in contact with the membrane. In this process, pressure is used to push water molecules through the pores of a membrane while retaining the colloidal solids and salts. Typical operating pressures range from 450-600 psi.

Preconcentration of sweet whey before evaporation allows for more energy efficient removal of water at lower solids and increased capacity of existing evaporators. Total solids (TS) levels of 10-25% can be obtained in an efficient, practical manner. Reverse Osmosis membranes are used to remove water and will not alter the relative composition of the sweet whey components. Permeate quality from RO systems depends on the quality and composition of the feed and the level of concentration. The higher the TS, the greater the amount of constituents in the permeate. Typically, RO permeate will contain small (but measurable) amounts of organic solids. The process performance is greatly affected by operating parameters such as feed flow rate, pressure, temperature, pH and micro-biological quality of feed stream, feed concentration and fouling characteristics of the membrane for various components.

Filtration Applications


Other

Rinse Recovery

Reclaiming water from condensate, rinsing operations, and low-solid effluents allows you to find hidden value from your process and waste streams. RO technology will allow you to recover up to 90% of the volume of waste waters that would be lost through discharge. Water recovery benefits you buy: lowering water costs, reducing energy costs, decreasing raw water treatment costs, reusing valuable resources, and compliance with regulatory standards.

WPC Concentration

A combination of RO and NF can be used to concentrate whey product streams. Through these system applications levels of 30-40% TS are obtainable. These applications allow UF operation at lower solids for better efficiency and higher protein yield. These processes improve drying operations by lowering energy consumption and improving bulk density.

Polishing of Cow Water (Evaporator Condensate Polishing and RO Permeate)

Water recovered from processes such as evaporation or membrane processing can be subsequently handled and treated in such a manner that it can be considered a safe water supply ("acceptable process water"). Acceptable process water is suitable for intermixing with products for human consumption in certain specified applications.

Criteria for acceptable process water are detailed in USDA-Dairy Division item 113 and 115.

Reverse osmosis (RO) polishing of the streams can produce water that can be used directly for washing applications excluding final rinses of processing equipment. Polisher permeate can be further conditioned to meet potable water standards. Potable water, which may be used for final rinses, must meet the following standards:

Maximum Chemical Oxygen Demand 12 mg/l (ppm)
Maximum Chemical Oxygen Demand 12 mg/l (ppm)

Mechanisms must be in place to assure that the permeate is maintained at or below these levels. Approved chemicals, such as chlorine, with a suitable retention period may be used to suppress the development of bacteriological growth and maintain a COD value of less than 12 ppm. The addition of chemicals shall be by an automatic proportioning device prior to the water entering the storage tank to assure satisfactory quality water.

State regulatory agencies will require submission of paperwork for the process water. Paperwork includes but is not limited to; a flow schematic of intended distribution, intended uses and application, and consent to perform the required tests of water quality.

Concentration of UF Permeate

Permeate from the ultrafiltration of whey is a stream that is low in total solids (TS), typically 3.5 - 5.5% TS. UF permeate is usually 75-85% lactose on a dry basis, and is utilized for harvesting lactose or as cattle feed. Removal of water from this stream prior to further processing or transporting is essential to the economic feasibility. Membranes can be used to effectively increase the solids levels to 15% to 25%. Temperature and pH are critical factors determining the final concentration level. Due to the concentration of salts and sugars, UF permeate has osmotic pressure much higher than most other dairy streams.

At concentration >20% TS, nanofiltration membranes are occasionally used. Nanofiltration membranes will negate the effect of increasing osmotic pressure found at these TS levels. The volumes of permeate required to increase the TS levels in this range are quite small. Permeate from nanofiltration membranes at this point in a system tends to be higher in organic material.

Concentration of UF Permeate

Ultrafiltration

Milk

Whole Milk

Whole milk can be concentrated with Ultrafiltration (UF) to 1.5-3X volume concentration factor (VCF).

UF refers to a pressure driven membrane separation technique in which a membrane is employed to separate different components in a fluid mixture. UF membranes have pore sizes less than 0.01 micron. Separation occurs based on molecular size and chemical interactions between the membrane and fluid components that are in contact with the membrane. In this process, pressure is used to push water molecules through the pores of a membrane while retaining the colloidal solids and salts. Typical operating pressures range from 30-150 psi.

Permeate generated during processing is a lactose rich (65-80%) stream with ~5-6% TS.

The process performance is greatly affected by operating parameters such as feed flow rate, lower pressures, temperature, pH and micro-biological quality of feed stream, feed concentration and fouling characteristics of the membrane for various components.

UF preserves the functionality of proteins and the product does not have a cooked flavor. Processing temperatures of whole milk are typically < 50°F. Whole milk can be concentrated for several reasons: reduced volume for transportation, increased production capacities, or increased protein content.

Filtration Applications

Skim Milk

Skim milk can be concentrated with Ultrafiltration (UF) to 1.5-10% volume concentration factor (VCF).

UF refers to a pressure driven membrane separation technique in which a membrane is employed to separate different components in a fluid mixture. UF membranes have pore sizes less than 0.01 micron. Separation occurs based on molecular size and chemical interactions between the membrane and fluid components that are in contact with the membrane. In this process, pressure is used to push water molecules through the pores of a membrane while retaining the colloidal solids and salts. Typical operating pressures range from 30-150 psi.

The process performance is greatly affected by operating parameters such as feed flow rate, lower pressures, temperature, pH and micro-biological quality of feed stream, feed concentration and fouling characteristics of the membrane for various components.

UF preserves the functionality of proteins and the product does not have a cooked flavor. Processing temperatures of whole milk are typically < 50°F or 120°F. Skim milk can be concentrated for several reasons: reduced volume for transportation, increased production capacities, or increased protein content.

Filtration Applications


Whey

Sweet Whey (pH 5.8 - 6.5)

Production of WPC35-WPC65

A complete process scheme to handle and process whey to produce whey protein concentrate (WPC). Whey is a "by-product" of cheese making; approximately ninety percent of the milk volume is generated as whey during cheese manufacture. The whey is rich in whey proteins, which provide a good nutritional source and serve to impart excellent functional properties in various products when used as specially formulated additives. However, whey proteins constitute only ten to twelve percent of the total whey solids and require further purification before their properties can be efficiently exploited.

The process begins with a fines saver to remove cheese fines from sweet whey and sequentially proceeds through tanks, pasteurizer, separator, and ultrafiltration. This process scheme will yield product that ranges from 35% to 65% WPC. A secondary product from the system is the lactose rich (i.e. 70-80%) permeate stream.

Filtration Applications

Projected UF Operating Parameters
Protein Level 35% 45% 55% 60% 65%
Volumetric Yield 17.5% 10.3% 6.1% 4.6% 3.4%

Production of WPC65-WPC80

A complete process scheme to handle and process whey to produce whey protein concentrates (WPC). Whey is a "by-product" of cheese making; approximately ninety percent of the milk volume is generated as whey during cheese manufacture. The whey is rich in whey proteins, which provide a good nutritional source and serve to impart excellent functional properties in various products when used as specially formulated additives. However, whey proteins constitute only ten to twelve percent of the total whey solids and require further purification before their properties can be efficiently exploited.

The process begins with a fines saver to remove cheese fines from sweet whey and sequentially proceeds through tanks, pasteurizer, separator, and ultrafiltration. This process scheme will yield product that ranges from 65% to 80% WPC. A portion of this system utilizes diafiltration water to “wash” some of the non-protein constituents from the product stream. A secondary product from the system is the lactose rich (i.e. 65-80%) permeate stream.

Filtration Applications

Production of WPI

The Whey Protein Isolate (WPI) Process train transforms pre-treated (pasteurized, clarified, separated) feed whey into WPI. It consists of three membrane systems placed in series:

  1. Ultrafiltration #1 - Whey to WPC35 followed by
  2. Microfiltration - Delipidization of WPC35 followed by
  3. Ultrafiltration #2 - Delipidized WPC35 to WPI

Diafiltration water is added to the MF and UF #2 systems. Plants that already produce WPC35 can directly incorporate the MF and UF #2 systems to transform WPC35 into high value WPI.

The MF retentate stream is an additional source of income since it is a raw material for specific phospholipids, which have cosmetic and pharmaceutical applications.

A spray dryer (not shown in schematic) is used to convert UF#2 retentate (25% TS WPI solution) into WPI powder.

Overall WPI yield is ~ 0.5 lbs of powder per 100 lbs of whey infeed.

Filtration Applications

  UF#1 MF UF#2
Feed Whey WPC35 MF Permeate
Volume Conc. Factor 6 - 7 20 - 25 15 - 20
Membrane Type Polyethersulfone Polyvinylidene Fluoride Polyethersulfone
Pressure 80 - 120 psi 20 - 40 psi 80 - 120 psi
Temperature Cold (35-40° F) or Hot (~120° F)

Microfiltration

Raw Milk

Bacterial Reduction

The process of microfiltration is an integral part of producing Extended Shelf Life (ESL) milk, that has properties similar to HTST treated milk. Raw milk is preheated and separated, with the resulting skim milk then being microfiltered, during which the skim milk is then separated into a bacteria poor skim milk (permeate) and a bacteria rich skim milk (retentate). The retentate can be removed from the process or it can be mixed with a standard quantity of cream. The mix is then sterilized by high heat and reintroduced to the permeate. The blended milk is homogenized, pasteurized and packaged. The product can have up to a 45 day shelf life when stored below 43°F.

Whey

Fat Removal for WPI Production

The Whey Protein Isolate (WPI) Process Train transforms pre-treated (pasteurized, clarified, separated) feed whey into WPI. This process consists of three membrane systems placed in a series: Ultrafiltration #1, Microfiltration, and Ultrafiltration #2. In the process of Microfiltration of the whey feed stream there is separation of fat and phospholipids from whey, Non-Protein Nitrogen (NPN), lactose and minerals of a lower molecular weight. This MF retentate stream is an additional source of income since it is a raw material for specific phospholipids, which have cosmetic, nutritive, and pharmaceutical applications.

Discard Streams

Solids Recovery

Effluent within the wastewater treatment industry can be effectively treated through the process of microfiltration to concentrate rejected particulates for disposal. Suspended particles and microorganisms are filtered down to a particle size of 0.2 microns within this process. This allows for the receiving water source to be disinfected and protects the water if it is to be used as a recreational source or for surface water discharge.

Protein Fractionation

Separating Casein from Serum Protein Fractions

Microfiltration has proven to be an effective method of separating free B-casein protein, along with whey proteins and small micelles from a skim milk fraction. This microfiltration process requires cooling the feed stream to about 4℃, at which point the B-casein dissociates from the casein micelles after a period of time. The feed is then passed through a microfiltration system using membranes at the 0.1 to 0.2 micron pore size. The resulting permeate product is a modified milk protein fraction which closely resembles human breast milk and can be used as a protein base for infant formulas.

Nanofiltration

Whey

De-salting Whey with Diafiltration

Salt whey is the final whey generated while making cheese, and is high in salt and often high in fat content. This salty whey can be collected, temperature adjusted, and processed with membrane equipment to yield a “desalted” whey stream and a low BOD, high salt discharge stream. The published regulations that apply are summarized as follows. Promptly after collection in a sanitary manner, the salty whey must be heated to 125°F (minimum) or cooled to 45°F (maximum) and stored at that temperature until it is processed by the membrane system. The maximum age of salty whey before membrane processing shall be 60 hours, calculated from the time the first salty whey in the batch is produced until start-up of membrane processing of the batch. Processing includes a diafiltration step using potable water to “wash” additional levels of the salt from the whey solids into the permeate. The salty whey shall be membrane processed and diafiltered at 125°F minimum temperature. The processing time in the membrane equipment shall not exceed 18 hours. The FDA definition of dry whey specifies that its ash content range is 7-14%. The membrane desalting process must be continued until the retentate ash content (dry basis) is reduced into the 7-14% range. After being processed according to published USDA guidelines, the recovered whey solids may be added to whey or whey products for further processing for human food. The fat can be removed from the whey solids with centrifugal separation prior to or just after being processed in the nanofiltration system.

Nanofiltration refers to a membrane separation technique in which a membrane is employed to separate different components in a fluid mixture. A nanofiltration membrane has pore sizes in the range of 0.001-0.01 micron and separates based on molecular size and chemical interactions between the membrane and fluid components that are in contact with it. A nanofiltration membrane will permit the permeation of monovalent salts (i.e. NaCl), but will retain divalent salts (i.e. CaCl2), sugars, proteins, and other higher molecular weight components. In this process, pressure is used to push the relatively smaller molecules through the pores of the membrane. The operating pressures typically range between 400-450psi for processing.

Filtration Applications

Mineral Reduction of Whey

Filtration Applications

  1. Low rejection of monovalent salts.
  2. Diafiltration can be used during processing.
  3. Typical reduction levels up to 30-40%.
  4. Reduced effects of osmotic pressure.
  5. System construction similar to RO.

Acid Reduction

Parameter Whey NF Concentrate NF Permeate
Total Solids 3 - 6% TS 18 - 25% TS ---
pH 4.2 - 4.5 4.2 - 4.5 ---
DBO --- --- 1,500 - 2,500 mg/l

Other

Concentration of Blood Plasma

Porcine and bovine bloods can be collected and processed to generate product streams. Red blood is centrifuged with mechanical separators, yielding a 50/50 split of red cells and plasma. The red cells are usually made into blood meal. The plasma, which is very high in protein (65-75% db), can be dried and used as high-grade animal feeds. Nanofiltration systems are used to concentrate, and slightly desalt, the raw plasma from its native 7-10% total solids (TS) into product at 20-28% TS. Nanofiltration membranes allow some passage of salt, thereby permitting higher concentrations without the corresponding effect of osmotic pressure. Permeate from the nanofiltration system will be <1% TS, containing mostly salts and other small molecules.

During collection of the blood, sodium citrate is introduced. The citrate spray minimizes the coagulation of the blood and plasma streams. The blood is separated at collection temperatures, while processing of plasma is typically done at 75-85°F. The concentrated product is promptly cooled to <45°F. The raw plasma and concentrated products are perishable and must be handled accordingly.

Filtration Applications

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