“You should always use the KISS Method whenever you can – Keep It Simple, Stupid.” – Every Engineering professor ever.
There are multiple ways to generate chlorine dioxide for water disinfection on farms. The most popular ways are using a medicator, automated activation systems, and metering pump systems. All of them CAN work (in the same way you can use a screwdriver to drive a nail), but the metering pump systems are the easiest, most cost-effective, versatile and safest options on the market.
Medicators, or proportioners, are just that: They’re made for injecting chemicals at a set rate from a stock solution. To adjust the levels in the lines, either the stock solution or the injection rate must be adjusted.
To activate the chlorine dioxide, the stock solution contains both the stabilized chlorine dioxide and the activator. This creates gas formation and is extremely dangerous for the farm employees. This stock solution is also extremely aggressive on equipment. Not only will the medicator likely suffer extra wear and tear, but other equipment exposed to the escaping gas also will be subject to extra wear. Of course, this gas is the chlorine dioxide intended to disinfect the water, so if it is not going into the lines, it will take more stock solution to treat the water, and the cost goes up to the user. This setup is typically used with solid chlorine dioxide products (sachets and tablets), however, some producers are using liquid products in this way as well.
An important side note on medicators used for water treatment is that at some point these pumps will fail (like all equipment) without proper maintenance. Since water is used to move the motor of the pumps, all of it goes through the units. Most proportioners will allow water to pass through when they fail, but some will not. If one of these units is used for water treatment, there is a risk that water will be cut off to the animals when the unit fails.
Automated Activation Systems
Automated activation systems pull the chlorine dioxide precursor and activation products from the concentrated container and mix them to generate a high level of chlorine dioxide disinfectant that is then diluted to usage levels. These systems essentially activate all of the chemistry so that only chlorine dioxide is available. They are less hands-on than a medicator, but still require multiple steps for application.
First, the pumps required to get the product from the concentrate container to the stock container are traditionally venture-type suction pumps. Venturi pumps are infamous for their inconsistency production agriculture applications. This is why they’re typically only used for water-line disinfection, power-washing soap addition, and disinfectant application on walls. They’re finicky – for lack of a better term – and are affected by viscosity, incoming/outgoing pressure, and supply-hose diameter. They are also very susceptible to solids contamination in water.
After the concentrated chemicals are pulled from the containers, they react in a vessel of some type. This vessel is traditionally plastic for chemical resistance, and some have a vent to the outside because these chemicals have certain levels that will gas-off. Just like with medicator activation, chlorine dioxide gas is extremely dangerous to humans and corrosive to the farm-building environment. Once the chlorine dioxide has saturated the solution, it is ready to use.
The final step is for another pump to be used to transfer the chemical from the reaction vessel (now stock container) to the water line. Often this is a metering pump of some type and can be as simple as a medicator. If it is a metering pump, then the level in the lines can be adjusted to the preferred level for your program. If it is a fixed-proportion medicator, then the producer is at the mercy of whatever level is generated in the container, which is often lower than the necessary level for disinfection. Fluctuations in stock levels can also contribute to inconsistency with automated activation systems because temperature plays a direct role in the amount of chlorine dioxide the water can hold. Seasonal weather changes can force producers to adjust the pumps up or down, depending on their program.
Metering Pump Systems
Metering pump systems are designed to be the simplest way to apply chlorine dioxide chemistry. They are the only systems that allow for differing activation rates, depending on the expectations of the program. They also are the only activation systems that limit exposure of chlorine dioxide gas to farm personnel by generating the chlorine dioxide as part of the water system itself.
The process is simple – one metering pump for the stabilized chlorine dioxide and one for the activation acid. These two chemicals mix in an activation chamber and the activated chemical then goes into the water line. This makes application easy to control and less expensive because only two pumps are required (potentially with a water meter if not already present).
What’s great about metering pump systems, aside from two simple pumps, is the ability to adjust the activation levels based on your expectation of the water treatment program. Some producers like to partially activate the chemistry to extend the residual and to gain nutritional aspects of chlorite while still utilizing chlorine dioxide as an initial disinfectant. Other producers utilize the independent adjustment ability of the pumps to set a disinfectant level and separate pH level for the water. With other systems, the pH and disinfectant level are not independent of each other.
Written by Jesse McCoy, CWS – Business Unit Supervisor, Water Quality – Neogen Corporation