In this posting we will discuss an application where a farmer employed a Spartan Environmental Technologies ozone generator, a model AE13M, for use in an irrigation system to control biological growth. The farmer had been using hypochlorite solution for this application. Our client was not satisfied with the hypochlorite solution due to rising costs and the handling issues with the chemical. He felt that a system that employed ozone would be easier to use.
The irrigation system took surface water and pumped it through a pipe network to spray nozzles. The clogging of these nozzles with biological growth was the primary purpose for the ozone water treatment system. The irrigation system had a maximum pressure of 70 psi and a flow of 35 to 40 gpm.
As noted in a previous posting an ozone water treatment system is composed of three major subsystems: gas preparation, ozone generation and ozone water mixing. In this case the client opted to use an oxygen cylinder as a source of gas feed for the AE13M ozone generator. This provided a clean and dry source of oxygen for the application. Since the irrigation system only worked for a few hour a day, it was an economical choice for the application.
In terms of ozone water mixing, the design called for a side stream injection system. About half of the main flow was taken from the pipeline and fed, using a booster pump, through a venturi injector. This system was sized to pull about 15 SCFH of gas, containing the ozone, into the side stream. Since the pipe line had a pressure of 70 psi, the booster pump was required to provide a pressure to the venturi injector of 120 psi to support a pressure drop of about 50 psi at a flow rate of around 20 gpm.
The side stream sent a mixture of fine bubbles and water into the main pipeline. To mix the side stream with the main flow to injection nozzles were placed opposite of each other each taking half of the side stream flow. This created a mixing zone inside the main pipeline to insure that the full flow was evenly mixed with the ozone.
Since the ozone concentration was around 5%, 95% of the case was oxygen. This gas needed to be released from the main pipeline where it could gas binding in the rest of the irrigation network. To accomplish this a tee was added to the pipeline downstream of the injection point, but before the point where the water branched off into the irrigation network. A four foot standpipe was added to the tee with a flanged top. A gas relief valve was tied into the standpipe. Oxygen gas that accumulated in the standpipe was thus vented to atmosphere while maintaining the pressure in the line.
The system has operated as expected without incident. If you have an irrigation system, and would like to explore the use of ozone for maintaining the biological control of your pipe network, contact Spartan for additional information.