Between irreversible fouling and chemical degradation of the membrane: key operational parameters of CIP/SIP cleaning in cross flow membrane filtration systems to restore transmembrane pressure in milk and whey processing.
Cross-flow filtration technologies—reverse osmosis, ultrafiltration, nanofiltration, and microfiltration—have become the backbone of modern dairy processing. Their ability to concentrate milk in the direct manufacturing of dairy products by ultrafiltration (UF), cold bacterial clarification, whey valorization, or fractionation of high-value compounds (such as lactoferrin and serum proteins), among other applications; requires installations capable of maintaining continuous production runs.
However, operational yield depends directly on the physical state of the separation modules. Continuous exposure to complex fluids rich in denatured proteins, emulsified milk fat, and mineral salts generates severe fouling and scaling phenomena. Integrating equipment specifically engineered for CIP cleaning in cross flow membrane filtration systems is essential to restore permeate flux, control transmembrane pressure (TMP), and extend asset lifespan.
However, the performance of these plants depends directly on the operational state of their separation modules. Continuous contact with complex fluids rich in denatured proteins, emulsified fat matter, and mineral salts generates severe fouling and scaling phenomena. Integrating equipment specifically conceived for CIP cleaning incross flow membrane filtration systems is the indispensable condition to restore permeate flux, keep transmembrane pressure (TMP) under control, and extend asset lifespan.
Nature of fouling in dairy fractionation and concentration
Unlike metallic transfer lines or plate heat exchangers, polymeric and ceramic matrices possess microscopic pore geometries and flow spacers vulnerable to deposit buildup. During the process engineering and definition phase, four main types of fouling must be considered:
Protein scaling (gel layer): During milk or whey concentration, serum proteins (especially beta-lactoglobulin) precipitate onto the element surface, forming a dense hydrophobic layer that acts as a secondary hydraulic barrier.
Lipid deposits: Fat matter adheres to fine pores and drastically reduces the hydrophilic permeability of the matrix.
Mineral scaling (milkstone): Calcium phosphate and citrates precipitate in the pores when salt concentration increases in the retentate stream.
Microbiological biofilms: If sanitation is incomplete, bacteria find an ideal substrate in accumulated retentate to colonize the module’s internal structure.
Membrane types in the dairy sector and their impact on equipment design
In dairy processing, there is no standard cleaning recipe. Material selection and operational limits of the CIP skid are defined at the factory based on the structural material of the filter element and the process to which it is subjected:
A. Spiral-wound polymeric membranes (Polyamide, PES/PS, PVDF)
They are the most common due to their high separation surface density:
Polyamide (PA): Used in whey concentration and permeate condensate. Highly sensitive to oxidizing agents (free chlorine irreversibly degrades its active layer). CIP skid automation demands strict pH control limited to 10.5–11.0 and regulated disinfection with peracetic acid.
Polyethersulfone (PES) and Polysulfone (PS): Used in milk protein standardization and direct UF cheesemaking. They present higher thermal and chemical tolerance than polyamide, withstanding pH windows from 1.5 to 12.0, allowing aggressive alkaline washing cycles to remove dense protein loads.
Polyvinylidene fluoride (PVDF): Stand out for their mechanical and chemical resistance against oxidants, being common in clarification or complex protein fractionation processes.
B. Ceramic membranes (Titanium, zirconium, and alumina oxides)
Mainly used in microfiltration (MF) for cold bacterial clarification, casein separation, or fatty effluent treatment. Their structural resistance allows projecting installations prepared for extreme conditions: temperatures up to 85 °C–90 °C, pH values from 1 to 13, and direct SIP sterilization by clean steam or superheated water (thermal SIP).
Operational parameter matrix by filtration technology
Clean steam (> 121 °C) / Superheated water / Chlorine
Technical sources and references for parameters:
EHEDG (European Hygienic Engineering & Design Group): Doc 46: Hygienic Design and Operation of Membrane Filtration Equipment in the Food Industry.
IDF (International Dairy Federation): Bulletin 488/2017: Guidance on Cleaning and Sanitation of Membrane Plants in the Dairy Industry.
Cheryan, M. (1998):Ultrafiltration and Microfiltration Handbook, Technomic Publishing.
Tamime, A. Y. (2013):Membrane Processing: Dairy and Food Applications, Wiley-Blackwell.
Chemical regeneration strategy: formulation and compatibility
To remove deposits without degrading the active layer, the CIP installation must execute sequential and automated reagent dosing:
Formulated alkaline detergents: Solubilize the protein gel layer and saponify lipids. In organic elements, buffered formulations with chelating agents (such as EDTA) and surfactants are used to keep the pH within limits preset in the control recipe.
Formulated acid detergents: Dissolve calcium phosphate and milk salts lodged in the pores (phosphoric/nitric acid buffered to pH 2.0–2.5) protecting internal gaskets, seals, and spacers of the module.
Enzymes and cleaning boosters: In UF cheese concentrates, retained organic matter requires soaking or recirculation stages with specific enzymes (proteases and lipases) at mild temperatures (40 °C–45 °C) and controlled pH.
Design, manufacturing, and commissioning criteria in Perinox CIP/SIP skids
Cleaning success in a separation system depends directly on how the equipment is projected and integrated into the line. At Perinox, we design, manufacture, and commission specialized solutions adapted to the needs of each project, applying industrial engineering criteria aligned with actual plant operation:
Custom mechanical and hygienic design: Manufacturing in stainless steel for parts in contact with product and chemicals), documented orbital welding, controlled internal surface roughness and self-draining pipe routing to eliminate dead legs.
Hydraulic management of transmembrane pressure (TMP): Skids are equipped with variable frequency drives and differential pressure instrumentation to adjust recirculation flow rate. This maximizes shear stress on the membrane while maintaining a reduced TMP that prevents dirt compaction in the pore.
Automation and recipe programming: Development of control software (PLC/SCADA) adapted to plant process logic. Allows parameterizing specific sequences (permeate pre-rinses, alkaline/acid washes, enzymatic stages, and rinses) ensuring strict compliance with thermal and chemical limits set by the module manufacturer.
Closed-loop concentration and temperature control: Automatic dosing using conductivity meters and tubular or plate heat exchangers integrated into the skid itself, guaranteeing washing cycle stability.
On-site commissioning and validation: Field adjustment of the equipment by specialized technical personnel, calibrating phase times, valve switching, and verifying optimization in water and reagent consumption.
Digital logging and traceability: Automatic monitoring and archiving of operational parameters (conductivity, pH, temperatures, pressures, and times) to ensure compliance with quality audits (HACCP/IFS/BRC) and repeatability of each washing batch.
Effectiveness metrics and flux recovery (NWP)
During the commissioning phase and routine plant monitoring, CIP/SIP system effectiveness is validated through quantitative indicators:
Clean water flux test (NWP – Net Water Permeate): Measurement of flow rate processing demineralized water at reference TMP and temperature. A well-dimensioned and automated skid restores NWP to values ≥95 relative to the nominal value of a new module.
Differential pressure drop: Confirms that flow channels and spacers are free of solids and precipitates.
A CIP/SIP system designed and custom-built for the installation not only guarantees the microbiological quality of the final product; it is the industrial equipment that protects the investment in membranes, avoids premature replacement, and optimizes water and chemical reagent consumption per processed ton.
