Ozone is the strongest disinfectant used in water treatment, so it’s important to understand a few key factors that improve the disinfection process. Operators have been using ozone for over 100 years to treat drinking water, so many improvements have been made in this time. Some basic principles are key to success in ozone installation.
- Know your water.
Yes, this is obvious before any installation, but happens to be overlooked too many times. You must know your water quality and your disinfection goals. A good first step would be getting representative samples of different treatment times, like the most common and most challenging conditions. These could be, but not limited to, peak demands, low flow, drought or seasonal change. A lab can run several tests that can be beneficial before installation. Lab tests include pH, alkalinity, total dissolved solids, total suspended solids, inorganics (anions/cations), specific metals and dissolved organics (such as TOC, color, BOD /COD, TOrCs, etc.). An ozone demand/decay test of a representative water sample offers a vital insight into the oxidative demand that must be met in order to achieve the targeted disinfection goals. While ozone disinfection is robust and highly effective under a wide range of conditions, a thorough understanding of your application can result in significant cost savings and performance benefits.
- Run a test.
Regardless of how much water quality data you have available, nothing beats an actual ozone demand/decay test for selecting the proper design. Fortunately, ozone disinfection designs are relatively easy to simulate in the lab and results typically scale up well. Select a testing facility that can replicate as many of your ozone disinfection process parameters as completely and accurately as possible. A good test will require only a few days or more of work to complete and should verify the most important design parameters. Although a good test may cost several thousand dollars, the results can help avoid very costly mistakes in the full-scale system.
- Look at the whole process.
Ozone disinfection is a treatment process, so when looking at the correct process, an operator needs to look at the whole thing, not just a collection of parts. An operator needs to select the best design and performance factors of ozone generator, injection and reactor systems. Most ozone generator systems can operate across a wide range of concentrations and power efficiencies. Similarly, modern ozone injection designs can accommodate a broad range of ozone concentrations, while maintaining high transfer efficiency. Balancing these factors with an efficient “CT” (concentration X time) is critically important to disinfection efficiency. In most cases, the best designs result from prioritizing most cost-efficient overall disinfection design over the performance of any one subsystem or component.
- Look to the future, but don’t overdesign.
Any time a system is going to upgrade a process in your treatment facilities, an operator must look at future needs. Traditionally, most ozone system designs include healthy doses of equipment overdesign and redundancy. Unfortunately, overdesign results in ozone generator equipment that operates well below its peak energy and cost efficiency. Worse still, redundant equipment is simply idle capital cost. Fortunately, newer ozone generator platforms offer flexibility for design and future expansion. New designs also reduce the need for standby equipment, while maintaining high levels of reliability and operational readiness. Limiting overdesign with an eye toward design flexibility can contribute very significantly to capital and operating cost savings over the life of a project.
- Minimize maintenance.
Every process must have minimal maintenance as much as possible. The more you have to work or spend on your ozone disinfection, the longer it will take to recoup the cost of the new system. Fortunately, newer technology of ozone generators has reduced the maintenance measures needed to operate on a daily basis. The main reason for maintenance is due to infrequent and inefficiently operated ozone equipment. A long-term goal for maintenance should be planned at the start of a systems design process.
These are just a few keys that must be addressed when installing an ozone disinfection process. Always take the time needed to look over the whole process when making treatment decisions.