The MS2000 is a Total Trihalomethanes on-line monitoring system which provides low level measurements of THMs in water and it has been developed for the water industry.
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 monitor provides that facility, efficiently and accurately.
Measuring Total THMs with an accuracy of +/-10 ppb, 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:
|Range||0 – 200 ppb in water|
|Sampling Frequency||20, 30 and 60 Minutes|
|User Interface||8" resistive touchscreen|
|Data Storage||µSD Card and Internal Memory|
|Data Interface||4 – 20 mA, Profibus, Modbus, Wireless, USB|
|Alarms||x2 Via Relay Drivers, Levels User Definable|
|Operating Temperature Range||0° – 40° C|
|Water Temperature Range||1° – 40° C|
|Power Consumption||10 W Continuous (90-240 VAC or 24 VDC)|
|Consumables||GAC filter media, Air Filter every 6 months|
|Validation||Every 6 Months|
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 Monitor Datasheet.
The principle of operation of the MS2000 THM Monitor 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 Monitor sensor head, which respond to the THMs in the headspace. This response is then analysed 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.
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.
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.