The requirements to control bacteria in industrial applications where water suspensions and solutions are used are essential. Of special concern is when solids are used in a process and are in a suspension of particles 0.5µl and finer.
Many industrial systems such as hard disk texturing, planerization of sapphire disks, polishing of silicon carbide wafers, or super-finishing of medical prostheses, require sub-micron abrasives in a suspension. In some cases, multiple production lines are used, with miles of tubing and pumps delivering exact amounts of slurried suspensions to a silicon carbide wafer, hard disk or a computer read/write head.
In most cases, all these suspensions must pass through a filter before they are deposited onto the workpiece. These filters are usually 0.5µl or 0.75µl absolute in filtering capacity. Any particles that could quickly clog these filters, or to a greater detriment, pass through these filters, will lead to disastrous results. The bacteria in aqueous solutions are in the size range of these filters and can multiply rapidly during their reproductive cycle.
The mechanisms for disastrous results are two fold:
Bacteria that pass through filters can multiply in “dead areas” of a production system or be allowed to multiply during tooling or product changeover. If left unchecked, when the process is resumed, the “bloom” of bacteria is usually deposited onto the work piece and either destroyed by the process, leaving a disagreeable bio-film, usually in the form of lipoproteins or polysaccharide glycocalyx, which are difficult to clean, or the surviving bacterium is passed on to the next manufacturing cycle to repeat its reproduction. If passed onto an end user, the bacteria may lie dormant until conditions are right for reproduction at the customer’s facility.
Bacteria that are not passed through the filtering systems can be so numerous that they require frequent filter changes creating a potential maintenance nightmare, in which it becomes impossible to sustain a production schedule and orders cannot be met.
In the high end-manufacturing world, delivery schedules are tighter than deadlines in the daily newspaper business. Any delays, chronic or acute, in the production and delivery process inevitably create disastrous bottlenecks and poor results.
Sometimes there is a dollar penalty for late deliveries. With ever tightening margins and reputations on the line, on time or ahead of schedule deliveries become very important. Once an infestation begins, it is very difficult to eliminate and remain infestation free. It becomes paramount to ensure that the products manufactured and shipped in aqueous form are bacteria free.