UV Chamber Hydraulics and Dose Delivery
All particles or microbes see different intensities of light for different amounts of time. As a result:
- Several microorganisms found in purified water systems and WFI systems require higher doses than the industry standard of 30mJ/cm2.
- UV systems sized based on a non-validated dose are allowing pathways for organisms to pass through the system without receiving the customer’s desired dose level (minimum dose versus average/calculated dose).
- For single-pass UV applications, a system providing a non-validated 30mJ/cm2 dose may be delivering a dose closer to 20mJ/cm2 (or less).
- Bacillus and Burkholderia are more likely to be found in pharma water systems where non-validated, 30mJ/cm2 doses are specified. In addition, due to the theoretical calculations involved in non-validated systems, delivered doses may be below what is required for other, more prevalent organisms in both WFI and purified water systems such as Ralstonia, Pseudomonas, etc.
Endotoxin Removal
- Medium pressure UV doses greater than 500mJ/cm2 can remove >300EU/ml of endotoxin from the water.
- UV dechlor doses are >1000mJ/cm2
Microbiological Control
- Municipal wastewater samples were examined under a variety of conditions and treatment with UV. The selection of the type of UV lamp (LP versus MP) for wastewater treatment plants, as regards photoreactivation of total coliforms, is not critical as long as the applied germicidal UV dose is greater than 40 mJ/cm2.
- With UV dechlorination doses >1000mJ/cm2, this far exceeds the typical 30mJ/cm2 disinfection dose commonly used in post-carbon, pre-RO applications.
- These higher doses inactivate additional organisms that otherwise might survive low UV dose exposure (molds, spores, viruses, algae, Bacillus, Aspergillus, etc.)
- This high level of microbiological protection will help to reduce RO biofouling, minimize RO cleaning frequency (25-50%), and prolong the life of the RO membranes (10%-20%).
