Pure Ultraviolet

Ultraviolet (UV) technology was originally used to ensure the adequate disinfection of municipal towns’ mains water supplies. Since its introduction over 40 years ago, it is now applied globally for disinfection, total organic carbon (TOC) reduction, and destruction of ozone and chloramines, as well as dechlorination of process water in many different industries, including pharmaceutical manufacturing. Water is the material of the largest volume used within pharmaceutical processes and, driven by more stringent standards, increasingly sophisticated process barriers and disinfection techniques have been adopted. Several of the process stages in pharmaceutical production can themselves also cause microbial contamination, and UV can therefore be used as an effective barrier to ensure that discrete process stages do not compromise quality standards. Typical installations include UV for disinfection after carbon filters or before RO, and UV for disinfection and TOC reduction in the polishing loop. A correctly-sized UV disinfection system installed downstream of the carbon beds or directly upstream of the RO unit will eliminate at least 99.9 per cent of bacteria present in the inlet water.

DISINFECTION WITH UV TECHNOLOGY

UV disinfection systems are generally split into two distinct types: low pressure and medium pressure. Low pressure systems have a monochromatic UV output (limited to a single wavelength at 254nm), whereas medium pressure systems have a polychromatic UV output (with an output of between 240-310nm).

In essence, UV works by fusing adenine and thiamine molecules within a microorganism’s DNA, rendering it unable to replicate. The microorganisms are thus destroyed without the use of chemicals. Whilst 254nm is an effective wavelength for disinfection, it is generally accepted that DNA absorbs UV most effectively at 265nm (see Figure 1). Understanding these differences is fundamental to the design of efficient and effective UV disinfection equipment. Generally speaking, low pressure systems are best used on small, intermittent flow applications, with medium pressure technology lending itself to higher flow rates.