Aqua Metrology Systems


What is the THM-100?

  • The THM-100 is an on-line monitor for Trihalomethanes (THMs) and designed to be permanently installed at a water treatment facility.  The equipment is designed to operate 24 hours per day, seven days per week in an unattended fashion.  Results are available via a standard industrial (4-20 mA SCADA) connection, directly on the THM-100, or via e-mail and accessible from the Cloud.

What are Trihalomethanes (THMs) and why are they important?

  • Trihalomethanes (THMs) are produced as a result of the chlorinating raw water containing natural organic matter and consist of 4 compounds – chloroform, bromodichloromethane, dibromochloromethane and bromoform which are summed to produce a measurement of total THMs.
  • Since the 1970s, THMs have been documented to be geo-toxic and carcinogenic, meaning hazardous to embryos and cancer causing. Use of chlorine and any less than 100% removal of organics will result in some level of disinfection by-products (such as THMs).
  • Further, THM production is time and temperature dependent, with seasonal variations in the weather, especially rainfall, being a contributing factor.  Therefore, THMs can vary widely throughout the year depending upon the water source, weather, temperature, flow, upstream consumption and other factors.

How serious is the THM problem in the US?

  • Any water system can have THM issues, particularly at points at the extreme ends of the water distribution network where there is limited flow.
  • Under the previous method (Stage 1 rules), there were over 2000 violations affecting 725 water systems between July 2011 and June 2012.  Under the newer method (Stage 2 rules), even more systems are expected to be non-compliant.

How serious is the THM problem globally?

  • THMs are a concern globally anywhere surface water is processed into drinking water, and then distributed through pipes to consumers, as chlorine and chlorine derivatives are the most cost effective method to disinfect and make surface water suitable for drinking.
  • Methods such as UV, ozone, irradiation, and other such methods are useful only for point of use applications and can be extremely energy intensive.

Why is Chlorine used if THMs are so dangerous?

  • Chlorine and chlorine derivatives have been the least expensive way to disinfect water and make it suitable for drinking over the past 100 years and will continue to be so into the future for a municipal delivery system. Use of chlorine and any less than 100% removal of organics will result in some level of disinfection by-products (THMs, HAAs).
  • In many cases, chlorine dioxide, which reacts slower than free chlorine has been substituted for chlorine because it has a lower potential for THM formation, but still causes THM production.
  • Further, disinfection processes have been modified to include use ofUV, EDR, and other more costly processes in the effort to mitigate formation of THMs, but these techniques are significantly more expensive and do not provide residual protection for water in distribution pipes.

What is a safe level for THMs?

  • Current limits on THM concentration in treated water are 80 parts per billion (ppb) in the US. Many countries, such as Switzerland, Italy or Germany with limits of 25 ppb, 30 ppb, and 50 ppb, respectively, have more restrictive regulations.

How well understood is the process of THM formation?

  • The specifics of THM formation are not well understood and other than use of the THM-100, manual grab samples must be taken.  Direct measurement is the only way to assess the true level of THM formation.
  • Several water utilities and University organizations have developed models to predict the formation of THMs based upon analysis of certain precursor components in drinking water.  However, models are not yet sophisticated enough to reliably predict THM formation because of the number, complexity, and dynamics of the variables.

What do utilities do now to monitor for THMs?

  • The standard practice across the world is for utilities to take “grab samples” which are then taken to an analytical laboratory, often hundreds of miles away, for analysis. The results are then reported back to the utility in 3-10 days.

What is the problem with waiting 3-10 days to get back your THM results?

  • Within 3-10 days, the water has already either been delivered to customers in distribution pipes or consumed and the information is too late to proactively affect the process.

If a water utility were operating properly, would not the control systems be able to automatically control the level of THMs?  Why would you need an in-line monitor?

  • Raw water conditions change as a result of weather, precipitation, temperature, flow, upstream consumption and other factors.
  • Utilities have tried various instruments such as TOC (total organic carbon) and UV 254 nm monitors on raw water sources to predict final THMs levels. Unfortunately, these techniques have proven to be inaccurate, as the specifics of THM formation are not well understood and other than use of the THM-100, grab samples must be taken because direct measurement is the only way to assess the true level of THM formation.

Would the use of an in-line monitor, such as the THM-100, negate the need and costs of taking investigative grab samples at problem sites?

  • An in-line monitor would significantly reduce investigative grab samples, but probably not all.  Periodic samples may still be desired to validate operation of the monitor and take measurements at the terminal points, until sufficient statistics are developed to know the relationship between the output at the plant and terminal point.

Why should we use your tool to measure THM’s every couple of hours when we are only required to monitor monthly or quarterly.

  • Although monthly or quarterly THM samples are the only regulatory requirements, most utilities take significantly more THM samples to develop confidence that they will actually pass regulatory samples when tested.
  • The THM-100 simplifies the process of taking control samples and ensuring that the water stays within specification.

What could a utility do to eliminate the potential for any THM problem and therefore also eliminate the need for monitor?

  • To eliminate the potential for any THM formation, utilities must eliminate organics in the source water.  Utilities can treat water by adding more flocculants, granulated activated carbon, filtration, and aeration to eliminate organics.  These are either chemically, electrically, or process intensive processes which result in significantly higher production costs.

Suppose a water utility using the THM-100 identifies that it has a THM problem.  What can it do?

  • Utilities can modify the source water by blending their main raw water sources with water sources, such as those from bore holes or the result of reverse osmosis, known to contain fewer organics (dilution).  Alternatively, they can reduce the level of organics in the water prior to processing or more aggressively process the finished water as discussed above to remove THMs once they have been formed.

 The THM-100 can only identify that a utility has a THM problem, it does not fix it.  Why would a utility want to install your equipment if your equipment only highlights something, which a utility might not be able to fix?

  • No monitor ever fixes a problem.  However, more importantly, the THM-100 helps a utility to first identify that they have a THM problem and secondly, whether any fix it deploys is successful and cost effective.

How much does the THM-100 cost?

  • The THM-100 is priced consistently with other utility mounted equipment designed to operate continuously 24 hours per day, 7 days per week.
  • The technology was developed over a decade and the components proven to be reliable under continuous operation.

What certifications do the THM-100 have?

  • The THM-100 is CE Certified and has passed necessary safety and electrical tests, including EN 61326-1 (2006) the set of electromagnetic compatibility tests required for CE (conformance) certification.  CE certification is a requirement for selling any equipment in Europe.

How does the THM-100 work?

  • The technology behind the THM-100 is based upon a modified Fujiwara process.  The Fujiwara process was originally patented over 100 years ago as a lab based technique for THM measurement.  AMS automated a derivative of this process and are able to provide results well within the accuracy and repeatability of modern day lab capabilities.
  • The system automatically draws a sample, performs a Purge and Trap, Desorb, and Dissolve, reacts the resulting solution with a Chemical Reagent, then uses Spectrophotometric Detection to quantify the levels, and reports the results to the front panel, system database, and via any external display system such as Ethernet or 4-20 mA or over the internet Cloud.

Do you make sure the THM-100 maintains its accuracy?

  • The THM-100 contains 3 regents and 2 on-board standards.  The system runs a system validation daily and can be configured to run a full calibration as frequently as required, typically once per week.
  • Software continually monitors the performance of internal run-time parameters and alerts the user to the need for more frequent calibration if needed.
  • The THM-100 is as accurate and repeatable as typical lab performance.

Do you offer service contracts?

  • AMS and our distributors provide annual service contracts depending upon the monitoring need of the client.  Renewable annual service contracts provide on-site field service, preventative maintenance, software upgrades, remote data service and machine health monitoring.

What is the warranty on the THM-100?

  • AMS offers a standard 12-month manufacturer’s warranty.
  •  Longer duration warranties are available for purchase.

How large is the THM-100?

  • The THM-100 is nominally 2.0’ (610 mm) wide x 1.33’ (406 mm) deep by 4.67’ (1423 mm) high.
  • The system is designed to be wall mounted and weighs ~ 100 lbs (45 kg).

What utilities does the THM-100 require?

  • The THM-100 requires access to sample water; clean dry air, reliable   150 VA AC power, and a drain.
  • Specific utility specifications are available in Chapter 2 of the THM-100 manual.
  • A list of recommended air compressors and uninterrupted power supplies are available upon request.

What waste streams are produced?

  • The THM-100 produces two waste streams.  Processed water is send directly to a drain and is non-toxic.  Hazardous wastes are captured by the system in a 10-liter container and removed quarterly during reagent replenishment.

Can the THM-100 be used to monitor THM formation potential? Or, can measurements on the THM-100 at a waterworks be used to predict behavior in a distribution system.

  • Customers will typically use the THM-100 in conjunction with periodic downstream or tap measurements to develop a predictive model to forecast terminal point performance based upon measurements taken at the waterworks.

Is the THM-100 suitable for monitoring all drinking water sources?

  • The THM-100 is capable of handling both high chlorinated and highly brominated drinking water. A pre-installation survey is required to determine the correct set of reagents required for your specific water characteristics.

Is the THM-100 suitable for monitoring all waters including wastewater discharges?

  • The THM-100 is currently only designed to analyse the THM results in drinking water.  While it is anticipated that other water sources could similarly be monitored, please contact the factory to discuss any special requirements.

How do we get remote access to the measurement data?

  • Data is accessible through the front panel and via the internal database.  Remote access to the measurement data is available over e-mail, via the Cloud, memory stick or via an optional 4-20 mA connection.