Selecting ozone injection devices — Ozone Pump vs. Venturi
Oxidation is the first step of three that must be followed in order to be successful.
Before we discuss the specific ozone injectors available, let’s first quickly review a few ozone basics.
An ozone system designed to eliminate iron, sulfur and manganese for a well water application is made up of three main component groups. You will notice I use the words: “ozone system” not just “ozone” because ozone is merely a gas that accomplishes the oxidation process. Oxidation is the first step of three that must be followed in order to be successful.
The ozone process works in three simple steps.
Step one - ozone injection/oxidation. Ozone is tri-atomic oxygen (O3), which has very high oxidizing power. It is a gas produced from air and high voltage electricity. The injection of the ozone into the water produces tiny ozone bubbles, which saturate every drop of water. At this point, oxidation of iron, sulfur and manganese is immediate.
The ozone unit (ozonator) is the device that produces the ozone. Its design should be simple, waterproof, plastic/non-conductive housing, short-circuit protected by reset-table breaker, field serviceable and a stainless steel ozone generator construction.
Ozone must be injected into the water after it is produced. There are two methods that are most commonly used: 1) Ozone Pump - a positive displacement injector that pumps the ozone gas into the water similar to a chemical feed pump for chlorine; and 2) Venturi - device that restricts flow and pressure in order to produce a vacuum. This vacuum device sucks the ozone gas into the water. Improper sizing will result in insufficient ozone suction, which will cause insufficient oxidation.
Step two - aeration. The elimination (off gassing or venting) of the ozone and other gases/odors, such as sulfur, occurs by an ozone stripping action. As water flows down the Off Gas Tank, ozonated water rises and strips any gassing the incoming water.
Step three - filtration. The final step for removing the oxidized material is filtration. The media used should have: low water waste (backwash), high service flow, high removal capacity and requires no chemicals during regeneration. Mechanical filtration is all that is necessary if proper oxidation has been achieved.
An Air Oxidation system is set up the same way except, there is no Ozone Unit and the oxidation potential is far lower. Which means that an air system cannot eliminate iron or sulfur greater than 3 ppm, and typically cannot remove any manganese. Air injector systems also promote bio-slime growth and do not treat or sterilize the air being injected.
Selecting Ozone Injectors Criteria
Before you can select the type of injector you must first know what will activate your ozone unit. The choices are: Well Pump Pressure Switch and Flow Switch.
Using one over the other is based upon whether there is water usage other than in the home, and whether that other usage needs to be treated.
Fore example, a specific job has a 1 hp submersible well pump, bladder tank and pressure switch, house and underground irrigation system. The customer wants to treat only the house water.
If you electrically connect the ozone equipment to the pressure switch, you must inject your ozone into the water prior to the bladder tank. All the water will be treated and the ozone system will operate the entire irrigation cycle. This could cause an inordinate and unnecessary amount of wear-and-tear on the equipment.
Instead you should use a flow switch to activate the ozone equipment, not the pressure switch. You should also inject the ozone after the pressure tank, past the irrigation branch and on the house line only.
Flow switch operated ozone system must use an Ozone Pump. A Venturi will not be successful if used too far away from the high flow boost of the pump.
Ozone Pump vs. Venturi
There are only two possible and practical methods for injecting ozone into the water—Ozone Pump or Venturi. Both have advantages and disadvantages.
Ozone Pump. As mentioned earlier in the article, it is a positive displacement injector that pumps the ozone gas into the water, which is similar to a chemical feed pump for chlorine. There is no restriction of flow or pressure and it achieves the greatest volume of gas injection. This is an important factor when dealing with iron and sulfur over 3 ppm.
Venturi. This vacuum device pulls the ozone gas into the water. The exact gpm (gallon per minute) flow rate and operating recovery pressure must be established before selecting the correct Venturi. Improper sizing will result in insufficient ozone suction, which will cause insufficient oxidation and result in carry-over of what you are trying to remove. You cannot remove iron, sulfur, or manganese that is not oxidized! Booster pumps are used to increase the pressure prior to the Venturi thus increasing effectiveness. The disadvantage of the Booster pump is the increase cost, increase electrical consumption and noise.
Advantages - Venturi. They are low cost, have no moving parts, and require little or no maintenance.
Disadvantages - Venturi. It is critical to size the venturi correctly according to the gpm and psi. Incorrect sizing will result in insufficient ozone injection. The venturi must be installed in specific locations, which is close to the pump and prior to the pressure tank. Installing in the wrong location will cause the venturi to not create the proper suction. Pressure and water volume loss is typical and can be extreme. Booster pumps are needed quite often depending upon the hydraulics of the system.
Advantages - Ozone Pump. Ozone Pumps can accomplish injection in any location. They inject high concentrations of micro-bubbles based upon Henry’s Law of Physics. The benefit is the ease of installation, sizing, higher volume of gas injected, and no restriction of flow or pressure. The Ozone Pump eliminates possible improper sizing and restrictions associated with Venturi and can inject 2.5 to 4 times more gas by volume.
Disadvantages - Ozone Pump. Cost, moving parts and periodic service. The frequency of service will depend upon the operating time and the environmental conditions. This service is easily accomplished with minimum parts called a rebuild kit.