The requirements for water disinfection for almost every use of water today are becoming more stringent. There is also more pressure to demonstrate that any disinfection process used is providing adequate disinfection at all times and under all conditions.

Microbiological grab sampling has historically been the standard for verifying disinfection performance in many water industries. This provides some confidence that proper disinfection is provided overall, but will not always catch a short term, transient event (a "spike" in a particular bacteria, for example). Also, even if a problem is caught, the samples may not be processed for hours, or worse, days after the sample is taken, leaving the system at risk during that time.

Ultraviolet Sciences, Inc. (UVSI) has designed a UV Intensity Monitor (UVIM) for its water treatment products that delivers continuous, real-time UV intensity readings, not reference levels normalized to an arbitrary lamp run-time. Continuous intensity readings remove uncertainty and ambiguity that is typical with UV systems today

The primary advantage for continuous, real-time dose monitoring is that the dosage can be monitored and adjusted "on-the-fly", ensuring that contaminated water never reaches the user. Continuous chlorine monitoring has been available for a number of years now, but no equivalent means of continuous, real-time dosimetry for ultraviolet disinfection systems has been available until very recently. These current UV dosimeter systems have many variables to balance to compute this dosage. These systems require multiple system inputs, requiring extensive data files and significant computation power in order to provide the instantaneous dose.

UVSI's unique UV reactor design allows for the generation of real-time dosimetry data in a very simple, straightforward manner. The applied dosage is simply a function of the UVIM reading and the flow rate. And this is all independent of lamp age or water quality. There is no need for multiple input devices, extensive data files, complex mathematical algorithms, or high speed computational power.

The chart below shows the Reduction Equivalent Dose (RED), as generated following the USEPA's Ultraviolet Disinfection Guidance Manual testing protocol, for the UVS322S-100 (100 gpm) UV disinfection system. These data are plotted against that system's UV Intensity Monitor (UVIM) reading for three different flow rates.

Additionally the UVSI products use fewer and shorter UV lamps. Therefore, when using UVSI products, maintenance costs are reduced because fewer lamps need to be replaced. Instead of changing 8 or 12 lamps, the end user is changing 1 or 2 lamps. The UVS series is smaller also, meaning less floor space is required for operation.

This graph shows that the RED vs. UVIM reading for the Ultraviolet Sciences UVS family of treatment chambers is linear over a wide range of RED's and UV intensities. This is a ramification of our unique UV reactor design, and is not seen with conventional UV reactors. This allows the user to know the dose applied inside the UVS chamber at the system's current flow rate, simply by knowing the UV Intensity Monitor reading. This is a real-time measurement and is accurate regardless of lamp age or water quality. The operator can utilize this information to make decisions to control the performance of the overall water delivery system, with the knowledge that the UV system has provided proper disinfection continuously throughout.

Ultraviolet Sciences offers NIST-traceable UV Intensity Monitors (UVIM) on all our UV treatment systems, which range in capacity from 1 GPM to 4000 GPM. We will offer a stand-alone real-time dosimetry as a feature on our systems this year.