Service Is Key to Membrane Separation

Maximize Profits with Regular Service to Keep Membranes in Top Operating Condition

Please use these quick links to navigate to a specific section of this page:

• Introduction
• The Basics of Dairy Membrane Filtration
• The Cleaning Dilemma
• The Essentials of Good Service
• Service Models for Optimum Operation

Introduction

Several years ago a large cheese plant in the United States added an ultrafiltration plant using spiral wound membranes to recover whey proteins. The plant was specified to run 2 million pounds of whey per day, producing an 80% whey protein concentrate (WPC). But upon startup, the WPC was only 75-77%. The lower quality concentrate had to be sold in a different market at a substantially lower price, costing the dairy about $15,000 a month in lost profits.

The plant manager tried everything, but the equipment provider wouldn't (or couldn't) find a solution. Finally, in frustration, the manager called GEA Filtration. Experienced membrane filtration service personnel flew to the plant immediately, evaluated the situation, and found a problem with the process design. They recommended changes, helped implement them, and trained the operators to run the system, bringing the WPC product up to the 80% spec.

This is just one example of the lost profits that can result from improper design, incorrect operation, and lack of knowledgeable service for membrane separation systems. But even under ordinary operating conditions, consistent service on a regular basis can help maintain peak efficiency and maximize profits from recovery of valuable fractions.

The Basics of Dairy Membrane Filtration

Every dairy is different. Each plant is unique, producing custom products from complex organic streams. Although all dairies process milk, milk streams differ depending on individual factors such as the breeds of cows, their differing diets, and differing environmental conditions. The dairy pool produces a very wide spectrum of products:

• Basic grades of milk, skim milk, and cream.
• Cheeses of various types and flavors.
• High-value proteins from sweet whey.
• Added-value milk products, including extended shelf life (ESL) milk
• Functional food and nutritional products like infant formula and nutritional bars.
• Nutraceuticals such as sports and performance products.
• Medical products for vaccines and wound healing.
• Healthcare products like shampoos and toothpastes.
• Animal feeds.

Cross-flow membrane filtration processes have become commonly accepted as the best technology for many sensitive dairy separations. It is a cost-effective means of producing very specific separations at low or ambient temperatures with no phase change. There are several basic technologies in widespread use:

• Reverse osmosis is an energy-efficient de-watering process often used to pre-concentrate dairy or food streams prior to evaporation.
• Nanofiltration can achieve very specific separations of low-molecular-weight components, used for recovery of hydrolyzed proteins, concentration of sugars, and de-ashing of dairy products.
• Ultrafiltration is used to concentrate and purify medium-to-high-molecular-weight components such as dairy proteins, carbohydrates, and enzymes.
• Diafiltration is often coupled with ultrafiltration for additional product recovery, using water injection to remove solubles and wash out low molecular weight materials.
• Microfiltration removes bacteria and spores from milk, separates suspended particles, and fractionates milk proteins, as well as recovering cleaning chemicals.

Separation membranes are made of various materials, with the most common and most cost-effective for typical dairy applications being polymeric. Polymeric membranes are available in spiral wound for high-volume applications with minimal or no suspended solids. Tubular configurations are resistant to plugging, so are typically used where there are suspended solids or fibrous compounds. Hollow fiber polymeric membranes have an extremely high packing density and open channel design ideal for low solids liquid streams where backwashing from the permeate side is desired. For strength and resistance to extreme conditions of pH, temperature, or solvents, inorganic membranes of ceramic or stainless steel are the material of choice. Ceramic membranes are often used in microfiltration for bacteria and spore removal.

Typical applications of membrane separation in the dairy industry include:

• Production of high-value whey protein concentrate (WPC) and whey protein isolate (WPI).
• Protein standardization of milk prior to cheese production to increase yield.
• Concentration and demineralization of whey to reduce energy costs.
• Reduction of BOD/COD loading from evaporator condensate and permeate streams to reduce the cost of wastewater treatment.
• Salt brine cleanup.
• Removal of bacteria and/or spores from milk or whey.
• Clean-in-place (CIP) caustic and/or acid clarification and re-use.

The Cleaning Dilemma

Cleaning is a very important part of milk processing because milk spoils easily, producing toxins and bacteria. Because of the nature of the milk stream, processing plants get fouled and must be cleaned every day. There may be complex built-up products from the organic milk streams, making cleaning difficult. Often dairies pre-treat feed to minimize fouling.

Typical CIP systems require three factors for proper cleaning: turbulent flow, chemical concentration, and high temperatures. Most polymeric spiral membrane elements are temperature limited to 50ºC (122ºF). There are also pH limitations because the membrane material is most often cast onto polyester backing. It is very easily hydrolyzed at high and low pH, so concentrated chemical cleaning is undesirable. And membranes are somewhat limited by structural integrity as to how much velocity and turbulence they will accept. So all three of the factors required for proper cleaning are limited.

Over the past ten years great advances have been made to improve the ease of cleaning and allow gentler, yet effective, cleaning. This has allowed more widespread use of membranes for separations and eliminated some of the problems associated with inappropriate cleaning. In order to clean properly, mild caustic is required, with enzymes to help break down fouling molecules and chelators to hold the broken-down products in solution.

In general membrane separation systems have a lower initial investment, but higher operating costs due to high cleaning cost. Procedures must be set for cleaning and followed strictly, with very little allowance for deviations. So service is crucial to make sure dairy operators are running the plant properly and cleaning it adequately and according to guidelines.

Certain types of membranes can be cleaned with chlorine, but many will not tolerate it. Ten years ago membrane service companies would get a couple calls per year because, oops, chlorine was put into the system by mistake and had destroyed the polymeric membranes. Dairy operations are more sophisticated now, with segregated systems so chlorine cannot come into contact with polymeric membranes. The general confidence level has gone up by an order of magnitude in the past decade.

The Essentials of Good Service

There are a number of things a dairy owner should expect in the way of service from a filtration membrane supplier. These can be broken down into four categories: training; oversight/ optimization; replacement membranes; and process testing / development / design.

Training: When a membrane filtration process is first introduced into a plant, the operators usually know next-to-nothing about the process parameters and operation. The initial service requirement from the filtration service company is proper training for both supervisors and plant operators. Consistent operations are absolutely essential for reliable performance of membrane separation systems. Since owners can't micro-manage every single process in the plant, a good service company is like a second set of eyes. Regular follow-up visits by the service technician will reinforce the training and correct any bad habits the operators may have developed.

Typically, when dairy management decides to implement a membrane filtration process, the membrane provider will design the system and either install it for the dairy or supervise in-house installation. As a part of assisting in the startup, the service company will train the operators for most efficient operation. Once the system is up and running, the membrane supplier's technical representative should stop in after one to three months to check on the process. Often the service technician will find that the operators have forgotten some vital point of their training or developed a bad habit that adversely impacts the separation. The sooner improper procedures can be identified and corrected, the better it is for optimum results. Even with processes that have been in place for years, periodic visits by the service company will ensure proper operation.

Oversight & Optimization: Proper operation of a dairy separation process will prolong membrane life. Membranes wear out gradually with constant use, and at some point the end product is not of sufficient quality. For example, in concentration of dairy proteins the protein is perhaps 99.5% retained the first day. After a week or two it drops to 99.4%, and so on until the membrane must be replaced. The point of replacement depends upon the value of the protein. When the lost protein cumulatively amounts to the cost of a new set of membranes, then it makes economic sense to change them. The decision to replace the membranes depends on the particular dairy's procedures, the value of the products, effluent standards, and possibly other factors, as well.

"We work jointly with GEA Filtration to decide when it's time to replace membranes," according to Rick Kaepernick, VP Operations for Hilmar Cheese Company of Hilmar, California. "It's definitely a team effort."

Often dairy management makes the decision to replace the membranes, but sometimes managers will attempt to delay the expense of replacement as long as possible without considering the economic consequences of the loss of valuable product. A good membrane service company will assist the dairy in making the economic analysis and balancing the lost profit versus the membrane cost. This is an invaluable benefit to the dairy looking to maximize profit.

Replacement Membranes: As noted above, organic membranes used for separation have a limited life span and need to be replaced periodically, usually about once or twice a year depending on processing rates and conditions. The more experienced the service technicians are with a particular dairy, the better able they are to know the replacement history and predict when new membranes will be needed. A good service company will stock sufficient membranes so that they are available when needed.

In the case of catastrophic failure of the membrane, e.g., if a polymer membrane is improperly cleaned or subjected to extreme conditions, quick supply is critical to keep plants operating. "Speed of replacement service is very important to us," says Larry Wintle of Agri-Mark/Cabot's cheese plant in Middlebury, Vermont. "Sometimes there's no indication the membrane is going bad. They just let go all of a sudden. When that happens, we need our membrane supplier to get them to us very quickly."

A service company may stock replacement membranes at a central storage location, have consignment stocks with the manufacturers, and even keep replacement membranes at strategic customers' sites, just for that eventuality. Quick replacement should be a top priority for any company that supplies membranes, and the best suppliers can have replacements to their customers days earlier than the run-of-the mill membrane manufacturer.

Process Testing, Development & Design: Top membrane suppliers often work with clients beginning in the process development phase. A dairy or other food processor might wish to isolate a particular compound from a process stream because of valuable functional properties. Pilot testing will determine how best to isolate the particular component. A few membrane suppliers have process engineering expertise, supplemented by applications centers and pilot plant facilities to help customers learn as much as possible about the compounds involved. A fleet of rental pilot plants can be delivered directly to the customer's site to establish separation data. The usual procedure is to begin with a small pilot unit to screen various membranes for feasibility, and once the best type of membrane is determined, further testing on a unit specific to the membrane type will refine process parameters.

Where the customer is looking at an established process with no testing required, the supplier's process engineers can design a plant and generate a proposal based on capacity and product quality.

Service Models for Optimum Operation

There are as many service programs as there are membrane companies, but the best service comes from suppliers with process expertise. Unlike the membrane manufacturing companies, who understand materials science and production techniques but not process applications, a membrane filtration company should have a broad spectrum of process design capabilities. Not tied to any single manufacturer, these companies have a powerful knowledge bank covering both membranes and process applications. They are able to perform tests and design systems using the best available technology for the desired separation.

Service options are best described by looking at a particular example. GEA Filtration, a world leader in cross-flow membrane filtration, has established a membrane service program with three levels of service, designed to meet the needs of any dairy or other processor using membrane filtration. The three levels of service are the Membrane Replacement Plan, the Membrane Service Agreement, and the Membrane Maintenance Program.

Membrane Replacement Plan is quite simply the supply of membranes that enhance process performance at a competitive price. A large membrane stock and a very quick replacement time are key components. This plan is valuable to customers because GEA Filtration is one of the largest suppliers of membranes in the world. The company has relationships with all major membrane manufacturers and can leverage its buying power for the best prices and maximum manufacturer warranties. The program includes occasional visits by GEA's highly experienced service technicians, whose advice and recommendations can frequently help customers improve profit levels. This plan is available to any dairy, even those who originally bought from another supplier.

Membrane Service Agreement is a middle level of service from GEA Filtration. Service technicians and engineers assist the client by performing process audits and making recommendations for the best performance of all filtration systems in the plant. The client receives all the benefits of the Membrane Replacement Plan, with the added plus of having regular service visits that help optimize operations and keep processes running smoothly and at peak efficiency. The client also has access to GEA Filtration's design and process engineering group for any needs that arise.

Membrane Maintenance Program is the top level of service. A client signs a contract for a period of time, usually three years, and pays a monthly fee for process monitoring and all the membranes required. A dedicated service technician makes sure that all the membranes and process systems are in tiptop shape and operating appropriately. Constant observation through personal visits and reporting of data gives the service technician the information needed to optimize replacement time, and at that point replacement membranes are provided. If there is any type of problem, a call to the service technician will bring instant help.

"At Hilmar we're all about long-term relationships. We think it's an integral part of our business and how we've developed," says Kaepernick, a Membrane Maintenance Program customer. "We work together with GEA Filtration as partners. Trust is a big issue. I've got to know that if something isn't working, GEA is going to fix it. And they have delivered very, very well."

At this level of service, it is in GEA Filtration's best interest to make sure all membranes are being operated properly to maintain maximum life, because GEA is assuming the risk for problems and catastrophic failure. Therefore service technicians are checking on the plant regularly, talking with the operators, and getting copies of log sheets. Once a year the operators are retrained to ensure compliance with proper procedure.

The Membrane Maintenance Program has a number of major advantages for the customer:

Dedicated Service Technicians are the reason that GEA Filtration is able to offer so many levels of customized service. Their primary job is to travel from plant to plant, maintaining facilities with membrane maintenance or other service agreements. These permanent personnel are trained experts, each with 10 -15 years of fulltime experience in servicing membrane separation systems. They work with membrane separations every day, loading membranes, training operators, reviewing process logs, and maintaining contact with customers. They are so highly experienced that they can diagnose most common problems by simply looking at a membrane from a filter. Service technicians also understand regulatory agency requirements and reporting. They even have knowledge about the process control systems, including how the logic functions.

All GEA Filtration service technicians come from practical technical backgrounds and have the skills, common sense, hands-on capabilities and mechanical minds that allow them to go into plants and diagnose problems. Each service technician covers a dedicated geographic area and builds close working relationships with customers in that area.

The service technicians are supported by a large process engineering department at GEA Filtration headquarters in Hudson, Wisconsin. If there is an unusual problem, the process engineering section is a resource. The engineers will ask detailed questions to pinpoint a problem, and even make plant visits when necessary. This department also does development, process design, and sizing of new systems based on pilot plant data. They can recommend portable pilot plants for testing at customer sites where needed.

Engineering, design, fabrication, and installation of membrane filtration systems are all very important. But the day-to-day operation, maintenance and servicing of a system are the keys to maintaining profit levels for dairy owners.