The what, why, and how of industrial bacteria control in aqueous storage of synthetic diamond suspensions or non-organic suspensions.

Needs Identification
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 0.5µ and finer. Many bacterial species are around the size of 0.5µand finer.Viruses, by comparison, are generally in the angstrom size range.

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 slur-ried suspensions to a silicon carbide wafer, hard disk or a computer read/writehead.

In most cases, all these suspensions must pass through a filter before they are deposited onto the workpiece. These filters are usually 0.5µ or 0.75µ 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 filtersand can multiply rapidly during their reproductive cycle.

The mechanisms for disastrous results are two fold:
1. Bacteria that pass through filters can multiply in "dead areas" of a production system (e.g. elbows, tight curves, and low spots or sumps) 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 atthe customer's facility.

2. 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.

Bacterial infestations are more common in areas of the world where there is a good deal of humidity and moderate temperatures. However, they are not limited solely to those sections of our globe. 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.

In order to control a bacterial infestation, one must understand its sources. Bacterium, both good and bad, is all around us. The vector for infestation is usually through an outside source. Some examples are: a new chemical is added; process water is used that is untreated; ungloved human hands spread contamination; heating or air conditioning systems are turned on without cleaning; good management practices of employees are not practiced; or stored deionizedwater is not adequately treated, and so on.

Much like the common cold, once one production line is infected, they usually all become infected. The cost of replacing hundreds of feet of tubing per machine, e.g., breaking down and scrubbing metering pumps, wiping down the working elements of a production machine with sanitary wipes that cost $1.00/foot, results in production downtime and other costly activities.