Q: What are the operating pressure limits for Evolution membranes?
A: Evolution membranes are designed to be direct replacements for conventional sanitary membranes and are designed to have the same pressure limits. Pressure is mainly a function of the spiral element construction, so our membrane chemistry does not affect those limits.
Maximum operating pressures:
- Evolution Protein Concentration Membrane (PCM): 300 psi (20 bar)
- Evolution Superfiltration (SF): 580 psi (40 bar)
- Evolution Reverse Osmosis (RO): 800 psi (55 bar)
Q: How does the surface area of Evolution membrane elements compare to the surface area of conventional membrane elements?
A: The thicknesses of Evolution membranes are consistent with that for conventional polyester-backed membranes, so the membrane area of Evolution spirals is equivalent to conventional membrane elements.
Q: What is the molecular weight cut-off (MWCO) range for “tight UF” and “open nanofiltration (NF)” that Evolution SF membranes would replace? Please elaborate further on the type of membranes that Evolution SF would replace.
A: Evolution SF sanitary elements are ideal for the following applications: high-solids protein concentration, streams with high fat content, and protein concentration where NF is already being used (and lactose and ash rejection is not required).
Evolution SF replace tighter ultrafiltration (UF) membranes at the back-end of a system, such as those rated as 3 kDa and 5 kDa MWCO. If the UF membranes needing to be replaced are 10kDa or greater, then Evolution PCM should be considered.
Evolution SF may replace conventional piperazine-based NF membranes, often rated from 200 Da – 800 Da MWCO. An important question to consider when replacing NF membranes is: “What else does the NF need to retain other than protein in my product?”. Evolution SF is not designed to significantly reject smaller species like lactose or minerals.
For example, in whey protein isolate (WPI) production, an evaporator cannot be used to drive up the solids before drying because it will denature the protein. Instead, an approach is to use NF to remove water and drive up the solids before drying. If Evolution SF is used in this application, more lactose will pass and increase the protein even higher, resulting in a higher bulk density. Additionally, Evolution SF elements can be more simply and better cleaned than conventional NF elements, including using chlorine if needed.
Q: What is the typical operating pressure when replacing conventional NF with Evolution SF? Do you run into pump size issues when switching to Evolution SF?
A: Evolution SF membranes are a direct replacement for conventional membranes, and the same pumps and motors will be used when replacing NF membranes. Our experience is that Evolution SF will run at the same or lower pressure than conventional NF.
Q: Do Evolution RO membranes have the same oxidizer tolerance as conventional RO membranes?
A: Since Evolution RO still has a polyamide component, the oxidizer tolerance for Evolution RO is the same as that for conventional RO. Just like conventional RO, chlorine should not be used with Evolution RO membranes.
Conversely, Evolution PCM and Evolution SF membranes are chlorine tolerant with similar guidelines as conventional polyethersulfone (PES) UF membranes.
Q: What is the cost differential between Evolution membranes and conventional sanitary membranes?
A: Evolution membranes represent significant value creation for food, dairy, and biotech processors. Their pricing is commensurate with that value creation and will result in a lower total cost of ownership than conventional membranes.
ZwitterCo offers both a subscription model and direct sale model to make it easy for customers to try Evolution membranes and would love to demonstrate this with a trial at your plant. Please contact us to discuss further.
Q: How are ZwitterCo membranes different from charged PES membranes?
A: Though PES membranes are widely used for protein concentration, medical devices, and water and wastewater treatment, the inherent hydrophobic nature of PES, causing membrane fouling, is their primary disadvantage. Literature shows a significant amount of research on the modification of PES membranes via a number of methods to reduce fouling and improve performance. Despite decades-long research, commercial availability of charged PES membranes is extremely limited.
Technically, the primary approaches to develop charged PES membranes are modification of the PES polymer and surface modification. Despite past presentations regarding whey protein concentration with charged membranes produced via surface modification, the long-term success of these membranes has not occurred.
ZwitterCo membranes utilize a brand new zwitterionic copolymer chemistry. Rather than a step-change to existing membrane chemistry, ZwitterCo membranes represent a leap forward with a revolutionary anti-fouling membrane chemistry that has been shown in field operation to be permanent and stable.
Please visit our innovation page on our website to learn more about the chemistry: https://zwitterco.com/innovation/
Q: Your membranes have great potential, but I am concerned about the limited tolerance towards high temperature and high pH, which we rely on for sanitization in our production process. How do you ensure that your membranes are properly sanitized in processes that require it?
A: Systems cleaned and sanitized using high temperature and high pH are mostly found in Western Europe. Specific polypropylene-backed membranes, often referred to as pHT or HpHT, are sold for these systems.
The temperature specifications for Evolution membranes are equivalent to sanitary membranes produced on polyester backing – 55°C / 131°F for continuous operation and 50°C / 122°F for cleaning. Common sanitizing chemicals such as chlorine (though not for RO) and peracetic acid are used to ensure systems are sanitized thoroughly. ZwitterCo is collaborating with customers to explore higher temperature sanitization and has ongoing research to expand the range of Evolution membranes.
Q: What is the life expectancy of Evolution RO membranes, specifically in applications with 6-22% whey solids? What is the life expectancy of Evolution SF and PCM in applications up to 1.5X concentration factors?
A: Evolution membranes have not been around long enough to fully validate this; however, we expect them to last at least two and a half years in these applications.
We expect Evolution membranes to have longer operational life than conventional membranes because cleaning chemistry is the primary cause of surface degradation of membranes. Because less aggressive cleaning is required with ZwitterCo Evolution membranes, they should last longer.