TOC is an effective and fully accepted test for organic matter, but while TOC instruments have their place in certain specific applications, there is more than one kind of instrument that measures organics.
The measurement process that goes on inside a TOC instrument actually involves converting all the organic matter in the water to CO2. The quantity of CO2 produced is then measured by shining light through the CO2 chamber. The amount of CO2 indicates the amount of carbon which in turn indicates the amount of organic matter. It’s complicated but it does work.
The only problem is the complexity of the test. This complexity results in TOC instruments that are expensive to buy, are complicated to operate, and are difficult and expensive to maintain. Of course, these facts are often overlooked in a laboratory setting where operating conditions are close to ideal and servicing is relatively convenient. But what about the industrial, municipal and process control environments.
The truth is TOC instruments were originally designed for lab use and that is where they work best. After realizing there is a need for monitoring organic matter in real-time in industrial type environments, some TOC manufacturers have tried to re-tool their lab TOC instruments for continuous sampling with limited success. Industrial applications are a long way from the laboratory.
Fortunately, there is a clear alternative. There is a better method to measure organics for industrial applications. It happens that organic matter has an extremely high absorbance of UV light at the 254nm wavelength. This is the basis for the UV254 organics parameter.
In the past, UV254 has not had the sensitivity that TOC instruments do, although it should be noted that many applications do not require the sensitivity that TOC instruments provide. But now, with Real Tech’s new line of UV254 monitoring equipment you can finally measure on par with TOC instrument sensitivity at 10’s of parts per billion.
Some other UV254 monitors suffer from problems with measurement drift and inaccuracies over time. Real Tech’s patented technology solves the problems that other UV254 instrumentation has struggled with by continuously compensating for these fluctuations. Customers with prior negative impressions of UV254 instrumentation are always more than pleased with the performance of Real Tech’s instruments.
Some people wonder about interference from turbidity. The fact is that the levels of turbidity found in most applications are below 5 NTU and do not affect the UV254 reading. In higher turbidity waters we recommend a simple 5 micron filter to remove the bulk of excess turbidity. At the flow rates required the filter lasts a very long time before needing to be changed. Contrast this to an online TOC instrument. In side by side tests at an independent test site, an online TOC instrument from a leading manufacturer was constantly down after getting clogged by undissolved particles, while Real Tech’s UV254 instrument just kept purring along.
Other people ask us about correlations between UV254 and TOC. First off we have to say it is important to assess why you want to correlate to TOC. Perhaps you are a municipal plant and you have to perform quarterly TOC removal measurements across your plant for regulatory purposes. Although you may use TOC for reporting, this most definitely does not mean you should be using TOC for your organics removal process optimization (refer to our video presentation Coagulation Optimization with UV254). Keep TOC in the lab and use UV254 for process control and real-time monitoring. Another possibility is that a plant requires ultra pure process water for cleaning or cooling or other purposes. They might want to keep their TOC levels to a certain number of ppb. The bottom line is that UV254 will pick this up every bit as well as an online TOC instrument will. In the end, if you still want to see your organics content displayed in mg/L TOC that’s no problem. Correlations between UV254 and TOC are very linear for a given site or application. Many industrial applications can have correlations that approach 1.0 r^2 and even raw surface water going into a drinking water plant can be expected to have correlations higher than 0.9 r^2.
Finally, the price. Real Tech’s UV254 monitors range between $5-8k depending on the sensitivity and options requested. Options include dual feed which actually allows you to use 1 instrument for 2 measurement streams to allow percent removal to be measured across the process. Also, annual maintenance costs are under $100. Compare this with the price of a basic online TOC instrument at over $20,000 plus several thousand in annual maintenance. After 5 years, even a low end online TOC instrument will have cost you potentially well over $30,000 while you could have bought and used Real Tech’s UV254 monitor for only a fraction of that, all the while experiencing greater reliability and hands down a more friendly user experience.
A Real Tech representative will answer any questions you may have and we would be happy to discuss your particular needs.
Contact Real Tech today.
