Combating high TVCs in SSDs

Water purification systems play an important role in the healthcare sector. In hospital laboratories, for example, water is typically the most commonly used element and the quality of supply can be critical. Likewise, renal departments require a regular, reliable, high purity supply, not only to protect patient health but to avoid any failure that may result in a stressful disruption in service for patients. Meanwhile, Sterile Service Departments (SSDs) require large volumes of high purity water for a range of uses, from endoscope and equipment washing and sterilisation, to autoclaves, which sterilise equipment and supplies using high pressure saturated steam.

As part of the regime to continuously improve patient safety sterile services staff regularly monitor a range of criteria. These include the level of TVCs (Total Viable Counts) in final rinse water; this is generally where the operating cycle of each washer disinfector requires that equipment is rinsed after disinfection.

A TVC analysis of the final rinse water measures microbial purity; under the current HTM 01-01 guidelines, this should be no more than 100cfu (colony forming units) per 100mL of sample rinse water.

One of our leading heart hospitals faced a situation where it had high TVC counts on the final rinse water from a Radiology AER system. When the system was originally commissioned there was insufficient space to allow a full reverse osmosis system to be installed to provide high purity rinse water. Instead, an endoscope reprocessor using Peracetic Acid for the final rinse was chosen. However, the low level of Peracetic Acid used, at 12ppm, was insufficient to provide long-term protection; as a result, over time the level of microbial contamination gradually increased, leading to high levels of TVCs. Due to the nature of the machine, full disinfection was not possible, which meant that contaminated parts had to be replaced.

Subsequently, a review of the situation led to the specification of a compact reverse osmosis unit. Although this helped to resolve the immediate problem and brought the level of TVCs back within tolerance, the hospital team wanted to improve safety still further by testing the mains water, RO ring-main and final rinse water on a weekly basis. This led to the addition of a thermal sanitisation and chemical disinfection system to ensure that bacteria levels were consistently reduced to the required minimum.

Although this approach slightly increased the time required for each final wash rinse cycle, this was outweighed by the security and peace of mind that the revised system provided. Since installation, the hospital has enjoyed zero service shutdowns and excellent weekly TVC test results, demonstrating that establishing a tough monitoring regime, along with the help of a specialised water purification supplier, is crucial for patient safety.