by Ken Williamson, Alberta Agriculture, Red Deer Alberta
Ozone is an extremely reactive form of oxygen. It is composed of three oxygen atoms per molecule rather than the normal two. It is formed by exposing air to either an electrical discharge or ultraviolet light. There are many potential benefits in using ozone to treat dugout water. Ozone can be used to; (1) oxidize iron, manganese, and hydrogen sulphide (2) disinfect water (3) reduce organic colour (4) increase suspended particle size to help filtration (5) neutralize a variety of tastes and odours. Domestic size ozone treatment systems sell for $3,500 to $ 10, 000 and are sold by many water treatment companies.Ozone is fast acting and produces few undesirable by-products. Because ozone reacts with so many of the compounds found in dugout water it is imperative that enough ozone be generated and properly mixed in the water to do the job.
In the summer of 1990 an ozone treatment system was installed to treat and disinfect dugout water at a farm near Halkirk in east central Alberta. During the summer several bacteria tests came back positive, which indicated that adequate disinfection was not occurring. A co-operative venture involving Alberta Agriculture, the Alberta Environmental Centre, the water treatment dealer, and the farmer, was initiated to assess what was happening and what would be needed to correct the problem.
The ozone generator and samples of the water to be treated were tested by the Alberta Environmental Centre in Vegreville.
The ozone generator produced ozone at a rate of 0.7 grams/hour. Tests of the water showed that it took 23 milligrams/Litre of ozone to meet the total ozone demand of the water. A dose of 5 mg/L of ozone was required to get an acceptable bacteria kill. When this information was used to calculate an effective treatment rate, it appeared that there was only enough ozone being produced to disinfect this dugout water at a water flow rate of 2 Litres/minute. To effectively treat this water at a typical flow rate of 5 gpm (20 L/min) the ozone generator would have to produce 7 grams/hour of ozone. Unfortunately almost all of the domestic size ozone generators that have been tested at the Environmental Centre produce less than I gram of ozone per hour.
The alternate approach suggested was to set the treatment system up with the existing ozone generator so that water was treated at 2 Litres/minute and the treated water stored in a cistern. With proper design this equipment should be able to treat enough dugout water for a one or two household farmstead. Dugout water quality almost always deteriorates over the years. Any increase in ozone demand due to this deterioration would have an impact on system operation.