Water mixing in water treatment plant

Total Chlorine Measurement powered by Kuntze

Zirkon® DIS Total is an open potentiostatic sensor for measuring chlorine compounds.
Due to 12 mm design the sensor can be integrated in every Kuntze system.

Zirkon® DIS Total. A new dimension in disinfection.

No exchange of membrane
No exchange of electrolyte
No delicate plastic membrane
Immune to air bubbles
Due to the revolutionary material InnoDisk® the sensor Zirkon® DIS Total measures the following chlorine compounds:

Free Chlorine at high pH
Dichloroisocyanuric Acid
Trichloroisocyanuric Acid
BCDMH (1 Bromo-3-chloro-5,5-dimethylhydantoin)

Application: Swimming Pools (Public/Private)
Challenge: Chloramines/Solid Chlorine Reagents
Swimming Pools: Public – Chloramines

Chlorine is added to swimming pool water to kill germs and oxidize impurities, but when it binds to the body waste swimmers bring into the pool, it forms organic Chlorine compounds, largely chloramines. These disinfection by-products cannot be measured with a Free Chlorine sensor; a sensor for Total Chlorine is required.

Since those by-products can be harmful to the swimmers and corrosive to the installations, most countries limit the amount of organic Chlorine allowed in the pool water, and pool operators were amongst the first to ask for a continuous measurement of Total Chlorine.

One objective was to reduce cost and save energy through control of the filtration process based on the Total Chlorine measurement, to compensate for the noticeable amount of maintenance caused by that measurement – membrane-covered sensors are required that contain an active electrolyte, which has to be exchanged regularly, as well as the membrane itself. However, the concept never caught on.

The signal of a Total Chlorine sensor behaves differently over time, compared to a Free Chlorine sensor, so the difference between the two decreases over time, regardless of the concentrations. It can even drop below zero, showing Total Chlorine concentrations lower than the Free Chlorine, which is physically impossible, and simply a result of the different sensor techniques. Moreover, membrane sensors require regular exchange of parts, which is not only time-consuming but can also lead to operator-introduced errors or damage to the sensor.

With our new sensor Zirkon® DIS Total we are proud to be finally able to offer an open sensor for Total Chlorine, that contains no delicate membrane to separate the electrodes from the water. With its 12mm design, it is handled just like a Free Chlorine sensor and shows a similar ageing behavior. No exchange of membrane or electrolyte is required, so the performance of the sensor does not depend on the skills of the operator, and the maintenance requirements are just the same as those for the Free Chlorine sensor – while the sensor responds to the chloramines exactly like a membrane sensor, which was proven in extensive field trials.

Swimming Pools: Private – Solid Chlorine Reagents

While in public pools, inorganic Chlorine compounds (sodium hypochlorite, solid calcium hypochlorite or Chlorine gas) are used for the treatment, in private pools operators prefer solid Chlorine compounds – they are easier to dose, safer to store, do not change the pH of the water, and continue to release small amounts of Chlorine long after the dosing. Unfortunately, those stabilized products, mostly di- or trichloroisocyanuric acid, cannot be measured with a Free Chlorine sensor. More to the point, dosing of such chemicals cannot be realized based on a Free Chlorine measurement. And private operators are even less happy to use membrane sensors. Here again, the new open sensor Zirkon® DIS Total is the perfect solution, providing an easy-to-use sensor for a measurement previously fraught with problems.

Application: Drinking Water
Challenge: Chloramination/Free Chlorine at high pH
Drinking Water: Chloramination
Chloramines can also be found in drinking water – in some countries, a disinfection treatment is allowed that uses Chlorine and ammonia to form mostly monochloramine. Compared to disinfection with Chlorine, this is said to remain longer in the water and to form less by-products. However, it cannot be measured or controlled with a Free Chlorine sensor, it requires a Total Chlorine sensor.

Drinking Water: Free Chlorine at high pH
Another drinking water application that often uses Total Chlorine sensors is the treatment with bleach at very high pH. At pH levels higher than pH 8, the signal output of a Free Chlorine sensor is less than 25% of its value at pH 7. With the often very low concentrations used in drinking water treatment, this is not enough to allow a reliable measurement. Zirkon® DIS Total, on the other hand, responds not only to the hypochlorous acid that is the dominating form of Free Chlorine in water at pH7 and to which the Free Chlorine sensor responds. The Total Chlorine sensor also responds to its neutralized form, the hypochlorite ion. This is why in some countries, regulations even require the use of a Total Chlorine sensor, even though the water contains almost exclusively Free Chlorine, due to the absence of organic matter.

Application: Waste Water Treatment
Challenge: Final Chlorination
Waste Water Treatment: Final Chlorination
Treated waste water is sometimes disinfected prior to release into natural bodies of water to reduce the introduction of harmful bacteria, especially if that body of water is being used for recreation or as a source for drinking water. Waste water naturally contains much more organic matter than drinking water or pool water, so any Chlorine addition leads to the formation of organic Chlorine compounds. With its high load of particles, it requires a robust measurement unaffected by pollution. The new Zirkon® DIS Total with its bare Platinum electrodes is more robust and easier to clean than membrane sensors. Also, manual cleaning is not likely to damage the sensor.

Application: Industry
Challenge: Disinfection with Stabilized Biocides
Industrial Applications: Disinfection with Stabilized Biocides
Since industrially used water is not meant to come into contact with human tissue, a broad variety of biocides is registered. The main goal of disinfection is the prevention of biofilm growth, which can block pipes and heat exchangers, reduce the efficiency of industrial processes and increase the energy demand. Also, contaminated open circulation systems might release pathogens into the environment, most notorious among those the Legionella. To avoid corrosion, pH is usually above pH 8, so Free Chlorine is not well suited for these applications. Chlorine-Bromine mixtures are active at higher pH levels and still can be measured with Free Chlorine sensors, as long as the biocide is not stabilized. With stabilized biocides, however, the signal strength of the Free Chlorine measurement depends on the ratio Chlorine:stabilizer – if the stabilizer is not dosed separately and based on water volume, such treatment cannot be controlled with a Free Chlorine measurement.

The new Zirkon® DIS Total has proved to be capable of measuring several stabilized biocides over long periods of time. However, considering the broad range of biocides available and the little information about their chemical composition and its effects on the measurement, any new biocide has to be tested to ensure that the measurement is suitable.