Total Trihalomethane (THM) Analyzer

The MS2000 is a Total Trihalomethane on-line analyzer which provides measurements of THMs at low concentrations in water.

Regulations limiting the levels of Disinfection By-Products (DBPs) such as Trihalomenthanes (THMs) in drinking water have made the ability to measure DBP levels throughout the distribution network essential. Multisensor’s THM analyzer provides that facility, efficiently and accurately.

Measuring Total THMs with an accuracy of +/-10%*, the MS2000-SYS provides the confidence that is needed in a process control instrument which is vital in meeting regulatory and legal requirements. It is designed to:

• Analyze THMs post treatment
• Monitor THMs in the distribution network
• Monitor THMs post-chlorination for enhanced process control
• Calculate THM Formation Potential (Optional)

Features and Benefits

• No sensor contact with water: low maintenance, no sensor cleaning
• NO REAGENTS: low running costs
• The most cost effective solution
• High sensitivity: ideal for potable water
• Alarms to SCADA and other communication interfaces

For more information on the principle of operation, click on the FAQs tab.

*Below 20 ppb, it's +/- 5 ppb

THMs and the risks to health

Trihalomethanes (THM) are a group of four chemicals that are formed along with other disinfection by products when chlorine or other disinfectants used to control microbial contaminants in drinking water react with naturally occurring organic and inorganic matter in water.

The THMs are Chloroform (CHCl₃), Bromodichloromethane (CHCl₂Br), Dibromochloromethane (CHClBr₂), and Bromoform (CHBR₃). National regulatory bodies set limits for the level of THMs in drinking water which, in most countries, are tested on a regular basis at the customer’s tap.

They are Cancer Group B carcinogens (shown to cause cancer in laboratory animals). Chloroform is by far the most common in most water systems. Dibromochloromethane is the most serious cancer risk, (0.6 µg/l to cause a 10^-6 cancer risk increase) followed in order by Bromoform (4 µg/l), and Chloroform (6 µg/l).

THM levels tend to increase with pH, temperature, time, and the level of "precursors" present. Precursors are organic material which reacts with chlorine to form THM's. One way to decrease THM's is to eliminate or reduce chlorination before the filters and to reduce precursors. There are more precursors present before filtration, so it is best to reduce or eliminate the time chlorine is in contact with this water.

The US EPA, for example, has indicated that the best available technology for THM control at treatment plants is removal of precursors through "enhanced coagulation". Enhanced coagulation refers to the process of optimizing the filtration process to maximize removal of precursors. Removal is improved by decreasing pH (to levels as low as 4 or 5), increasing the feed rate of coagulants.

How does the Total THM Analyzer work?

The principle of operation of the MS2000 THM Analyzer is the measurement of headspace gases from a sample tank containing the water to be measured.

Through the use of Henry’s Law the concentration of gases in the headspace is proportional to the concentration of the substance in the water.

Calibration of the instrument is done by presenting a known concentration to the sensors and generating calibration coefficients from the responses obtained.

The MS2000 works by passing water through a sample tank as shown below. The volatile components in the water will pass into the headspace above the water where they will be trapped. This will continue until equilibrium is reached.

A sample of the headspace gases are then passed across sensors in the MS2000 THM Analyzer sensor head, which respond to the THMs in the headspace. This response is then analyzed by the instrument and a concentration value is generated based upon the relationship between the concentration present in the headspace and that in the water.

Calibration

For the detailed calibration technique see MS2000 Operation and Maintenance Manual. The technique is to present standards of THMs in water to the instrument. Multisensor recommends that this process is carried out in their factory and a pre calibrated sensor head is fitted in the field.

Validation of systems in the field is achieved using the Multisensor Validation Kit which presents a standard concentration to the instrument.

What does the MS2000 THM Analyzer actually measure?

The MS2000 measures the concentration of Total Trihalomethanes in water, which is given by the sum of chloroform, bromoform, Bromodichloromethane and Dibromochloromethane.

How often does the instrument provide a reading?

Compared with other on-line parameters, THMs tend to vary slowly over the course of the day. The MS2000 Total THM analyzer provides a reading every hour which is far quicker than our nearest competitor (once every 4 hours)

What is the reported value?

The instrument will report the Total THMs value.

How is the MS2000 calibrated?

The instrument is factory calibrated against a chloroform standard. Other requests can be considered

What is the required maintenance? Is it expensive?

The instrument requires a service every 6 months which include a sensor replacement as part of the low cost service pack. This is part of a sensor replacement scheme which can be discussed with Multisensor or your distributor.

What is the warranty?

Every instrument comes with 1 year warranty from the shipment date

What are the advantages of using e-nose technology?

E-nose technology allows for non-contact measurement meaning that:

• fouling of the sampling system is minimized through large diameter tubes being used
• suspended solids and dissolved chemical compounds do not coat or damage the sensors or optical components as used in Ultra Violet, Infra Red or Laser spectroscopy systems, extending their lifetime and reducing cleaning requirements
• no reagents are necessary as for instruments which use colorimetry as their detection technology
• no purging gases are needed as for GCMS based systems

How much water does the MS2000 use?

The MS2000 uses up to 1 litre per minute, which is simple to dispose of, but since no reagents are used the water could be returned to the water supply.

Is the MS2000 sensitive to environmental conditions?

The MS2000 employs temperature and humidity control and compensation techniques to remove the effects of these parameters. Some volatile chemicals can be an interferer, but if these were found in any concentration in drinking water, where the MS2000 would be employed, they would represent a serious health risk in themselves.

What are the System and Monitoring Options

The MS2000-SYS is packaged in a small enclosure and requires no additional chemical reagents for operation. The system includes both the measurement instrument and the sample presentation system, to allow the simple fitting of the unit within existing facilities.

A variety of communications options can be provided including 4-20mA loop, Wireless, Modbus and Profibus. The sensors can detect Total Trihalomethanes, or TTHMs including Chloroform, Bromoform, Bromodichloromethane and Dibromochloromethane.

For more information, please download the MS2000 Total Trihalomethane Analyzer Datasheet.