The need to reduce waste solvent, especially in biopharmaceutical manufacturing, is driving companies that supply various types of equipment to design disposable pieces generally made of plastic. This equipment often is smaller and less costly than the traditional equipment it replaces, which can be an advantage where space and other resource constraints exist.
Single-use equipment eliminates the need for cleaning or cleaning validation in bioprocessing systems. If the need for these activities is eliminated, then so are the cleaning systems, labor and downtime associated with them. As one vendor points out, operator error and cross-contamination of products also are reduced or eliminated.
Although some of this new equipment still is being tested by manufacturers, there already are proponents; one company has designed a new bioprocessing facility around the disposable equipment.
Drum roll, please
One of the early entrants into the market for disposables is Steadfast Equipment Inc., Seattle, which introduced its disposable rotary drum filter in Fall 2001. It operates on the same principle as a traditional rotary drum vacuum filter. A drum, covered in filter media, is positioned on its side and partially submerged in a slurry. A vacuum pulls liquid (filtrate) through the filter media, leaving the solids deposited on the filter media as a cake. As the drum rotates out of the slurry, the cake on the filter media begins to dry and is eventually removed from the filter media, thereby regenerating the filter media so that the process can be repeated.
John Kossik, technical manager for Steadfast, says the disposable rotary drum filter was developed to be an economical, single-use device. He says in most cases the operating cost of traditional equipment — such as plate and frame, and leaf filters — is largely due to the manual labor involved in cleaning the filter after use and preparing it for the next use. The disposable filter’s price is in line with the operating costs associated with preparing conventional filtration equipment for a new batch.
The disposable rotary drum filter is a small (7 in. long and 6 in. in diameter, Figure 1), totally-enclosed device made of injection-molded plastic. It can be disposed of in the same manner as solid waste. The disposable filter operates continuously, which is in contrast to the traditional equipment it is designed to replace.
Kossik says the disposable rotary drum filter can process between 1 L/min. and 3 L/min., depending on the properties of the slurry. Throughput can be increased by operating two rotary filters in parallel. The construction of the drum is such that the extent of vacuum that can be used is not limited.
Although initially intended for use in pharmaceutical manufacturing, Kossik says the disposable device has piqued interest in the cosmetics and food processing industries. Of those companies currently testing the disposable rotary drum filter, only 30% are pharmaceutical manufacturers.
Disposable Rotary Drum Filter
Figure 1. Steadfast's disposable rotary drum filter operates continuosly, unlike its conventional counterparts. This eliminates the need for time-consuming cleaning procedures.
Ray Collins, senior specialist for Dow Chemical Co., Midland, Mich., says his group has tested Steadfast’s rotary drum filter in a laboratory application for separating transgenic proteins from corn. His group knew they wanted to use vacuum filtration and chose the disposable rotary drum rather than a funnel vacuum filter since it offered higher capacity. “The disposable rotary drum filter is very useful in biopharmaceutical applications where sanitary concerns are paramount.”
Collins’ group tested the filter for about two days, during which they encountered problems with coarse solids accumulating in the enclosed trough. The particles were between 500 and 1,000 m, but not very dense.
Kossik says the benefits of the disposable rotary drum filter are that end users’ capital and maintenance costs will go down. Since the device is totally enclosed, operators will not be exposed to the materials being processed. Also, a steady-state operation is easier to control and less prone to operator error.
The device is not for everyone, though. The types of filter media available for use with the disposable rotary drum may not suit all applications. Steadfast is working with a filtration media supplier to expand its offerings. Due to the size of the device, it will be difficult to retrofit the disposable drum filter into systems that use large filters.
Collins says the disposable rotary drum filter gave them some insight as to how a conventional rotary drum vacuum filter will work for their application. “Sooner or later we will use it again,” he says.
Filter in versatility
Pall Corp., East Hills, N.Y., introduced its disposable manifolded filtrations systems about a year and a half ago. Dr. Holly Haughney, vice president of biopharmaceuticals marketing for Pall, says manifold components include polypropylene filter capsules, valves and fittings, all of which are disposable.
The capsule filters, which come in sizes up to 30 in. in length, can be arranged in parallel for processing larger volumes or in series for pre- to final filtration (Figure 2). Since various filter media and membranes are available to fit the capsules, the system is versatile and can be designed for a number of applications. The amount of time the filter media lasts depends on the filter configuration, filter media and feed properties. Haughney says another advantage of the disposable system is that the components are translucent, so operators can confirm fluid flow.
The filter capsules are fully assembled, which reduces operator error and assembly costs. Another advantage is that the single-use filter capsules can be sterilized by gamma irradiation, eliminating the need for autoclave or steaming operations. Since the manifolded filtration train is used once, cleaning validation requirements as well as any infrastructure needed for a cleaning system are reduced or eliminated. These systems were designed for biopharmaceutical manufacturers that are concerned about cross-contamination of products. Haughney says there are about 100 of these systems in use.