In this posting we are going to discuss using an ozone generator in a system where the flow of water is intermittent. An example would be a well pump that is feeding a pressurized system. In these systems the pump comes on in response to a drop in system pressure. It is not good practice to tie the operation of the ozone generator directly to the operation of the pump for three reasons:
First, quickly turning the ozone generator on and off will reduce the lifetime of the dielectric elements which are critical components of the ozone generator. Thus the overall lifetime of the system is put at risk. Second, it takes some time for the ozone generator to reach steady state. If the system is only on for a few minutes, it is not likely that steady state operation will be reached. As a result, the amount of ozone production will not be accurately known. Third, the size of the ozone system would have to be increased to meet the peak pump flow versus the average flow rate. This means a larger ozone system would need to be built.
There are a few ways to apply ozone in situations with intermittent flow. First, an equalization tank can be used to smooth the flow in the system. The ozone system could then be positioned after the tank where it would receive a steady flow. Let’s assume that the flow to the system is intermittent, but on average the flow is 10 gpm. A properly sized tank can be positioned prior to the ozone generator whose level rises and falls, but the outfall is a constant 10 gpm.
Second, the liquid could be treated in batches. Even though this may be intermittent operation the period of operation could be extended to a longer period, e.g. hours of operation versus minutes of operation. A tank is allowed to fill and contents treated over a suitable period of time. The tank is emptied and then allowed to be filled again to repeat the process.
Third, for a small system, it might make sense to run the ozone generator continuously and waste the produced ozone when it is not needed. Essentially, if the ozone is not needed it is vented instead of being mixed with the water. During these periods the generator can be turned down to a low rate of production. The excess gas would be passed through the same ozone destroyer employed for the vent gas from the process. In this way, the ozone generator is not entirely shut down.
Fourth, an equalization tank could be used with an ozone system which is set up to recycled the water from the tank through ozone injection system continuously. The tank level will rise and fall with the flow of water to the system. A dissolved ozone monitor would control the ozone generator output to main the concentration of ozone in the tank. While the output of the generator would vary, it would generally run continuously if properly designed in terms of size and flow.
These are a few options for handling intermittent flow to an ozone water treatment system. These approaches will permit longer generator lifetime, better output control and optimized system size. Spartan Environmental Technologies supplies complete ozone systems for a variety of water treatment applications.