Authors: Vanessa Jürtz, Bjerregaard S.S. and P. Fogh. Date: February 2011
Contact: Adept Water Technologies firstname.lastname@example.org
Key words: drinking water, chlorine, current, voltage, cost, Bac Terminator, bacteria, disinfection
BacTerminator is a unit used for disinfection of e.g. drinking water without adding any chemicals to the water. The principle of BacTerminator disinfection is electrolysis, turning salt in the water into hypochloric acid and chlorine, thereby effectively eliminating bacteria and other microorganisms.
The BacTerminator's running cost is up to 75% less than that of other technologies and the BacTerminator is also more effective. When using a BacTerminator in a new application, return on the investment often begins on day one - in other applications replacing existing equipment, the investment is normally returned in one to two years.
The technology can be applied in several fields, including:
To demonstrate the impact of the salt content (here NaCl) and conductivity of the water on the power consumption of the BacTerminator different waters were analysed. In Figure 1 the power consumption and the cost related to this is shown if the BacTerminator produces 1 ppm free chlorine. If the concentration of salt (NaCl) in the water is above 100 mg/L the cost drops to a minimal level. The WHO guidelines for drinking water allow 250 mg/L of NaCl in drinking water.
The patented electrolysis method used by the BacTerminator to disinfect water runs particularly efficiently efficient if the Cl- ions are present in a sufficient amount and do not have to compete with a lot of other ions that can take part in the electrolysis process. In water that has a high conductivity but a low salt content, Cl- ions encounter a lot of competition with other ions and more energy has to be used to produce 1 ppm of free chlorine which turn increases the cost of the water disinfection process.
If the water to be disinfected by the BacTernminator has a low salt content and a high conductivity, the addition of salt (NaCl) can reduce the cost of the process tenfold. This is shown in Figure2 where the cost of treating the original water is compared to the cost of treating water to which 50 mg/L of chloride (Cl-) has been added. The salt costs much less than the power, so adding salt can save a lot of money.
Figure1 The cost and power consumption for running the BacTerminator to produce 1 ppm of chlorine. The cost depends on the chloride concentration of the water used for the process.
Figures 2-3-4-5 Comparing the cost for running the BacTerminator to produce 1 ppm free chlorine in original water and after adding 50 mg/L Cl- to the water. The cost of NaCl was added to the cost of power consumption. Adding NaCl can reduce the cost drastically, especially if the original Cl- concentration is low.
Waters with different NaCl concentrations were prepared, conductivity was measured and the waters were treated with the patented electrolysis method of the BacTerminator. Current and voltage were adjusted to different values and the chlorine production of the BacTerminator was measured.
Method, equipment, and reagents for determination of chlorine were obtained from Hach Lange. The standard reference instrument used for colorimetric measurement was the DR2800. Chlorine was determined with the LCK310 cuvettes.
The cost was calculated from the values obtained, assuming a price of €0.13/kg for NaCl and €0.1/kWh for electricity.
1) Krasner S.W. (2009) The formation of and control of emerging disinfection by-products of health concern. Phil. Trans. R. Soc. A 367:4077-4095