Q&A: On site but out of mind… getting extra mileage out of your disinfection system

Using on-site sodium hypochlorite generation technology to make oxidant for water and wastewater treatment is cost-effective, safe, and environmentally responsible. But, as with any piece of equipment, choosing the right one and caring for it properly impacts both life cycle costs and effectiveness. We talked with David McWalters, Field Service Manager-Americas, De Nora, to learn more.

When specifying an on-site sodium hypochlorite generator (OSHG), what kinds of considerations can impact asset life/maintenance?

System sizing is probably the most critical factor. If the system is undersized, it could be running 24/7, putting more wear and tear than the system is designed for. Knowing the sizing details from the earliest stage makes a big difference in a successful maintenance program.

Another consideration is the quality of the water. Using water that meets the system specification for hardness and other minerals will allow for the longest life of the system. Most OSHG manufacturers can provide ancillary equipment to resolve most problems with constituents in the water, knowing it up front is important. It’s very important to follow recommended maintenance on ancillary equipment, too. For example, an effective water softener will extend the life of an OSHG, but a faulty one can allow build-up on the cells and actually reduce the life of the system.

Like water, choosing a higher quality salt can also extend the life of the OSHG system. In the way that using a cheap oil in your car will affect the life of the engine, using inferior salt will affect the life of your electrolytic cell, the heart of the OSHG. When salt has a high calcium content, it builds up on cells and requires more cleaning. Some OSHG systems require food grade salt and others do not.

The environment also impacts the initial OSHG system design. Some considerations include the exposure to sun, heat, humidity, and potential for corrosion, particularly related to the electronics of an OSHG. Cells should not be exposed to direct sunlight so part of the design for an outdoor OSHG will include a covering. These variables should all be addressed at the time of specification.

How long will an electrolytic cell last?

We expect an average of 7 years’ cell life, although with proper care I’ve seen some last as many as twelve years.

Does the application of an OSHG system affect the maintenance schedule?

Yes. OSHG systems are used for disinfection of produced water in oil and gas, municipal drinking water and wastewater, industrial cooling tower water, power plant process water, and aquatics including swimming pools and large fountains. The quality of water and the harshness of the environment can influence the maintenance requirements.

Are OSHG systems safe? How do manufacturers ensure customer and community safety, either through design features or through maintenance recommendations?

OSHG is by far the safest method of disinfecting with chlorine since the raw materials are salt, water and electricity. During the electrolysis of brine, hydrogen, produced as a by-product, is safely contained, rapidly diluted, and vented to the atmosphere. It is important to have built-in safeguards including a hydrogen sensor to detect concentration of hydrogen above a certain level, an air blower to dilute the hydrogen to a safe concentration and associated controls to shut down the OSHG system and alert operators. Choose a vendor with a proven track record who supplies a system that has been designed with safety in mind.

What does a typical maintenance schedule look like for an on-site sodium hypochlorite generator?

There are daily, weekly and monthly recommended activities and this will vary depending on the application and use of the system. A reputable manufacturer can offer training, guidance and clear operations maintenance documentation.

The most important aspect of a maintenance plan is being proactive and performing maintenance on the manufacturers recommended intervals to maximize system reliability and longevity.

What are the benefits of maintaining a consistent schedule and what are the potential implications of not doing this?

The benefits of performing maintenance on the scheduled intervals are getting the most out of your asset. On the flip side, not maintaining a consistent maintenance schedule can result in a shorter lifespan for the equipment and unplanned down time.

What kind of maintenance is required for an OSHG system?

It depends on the location and application of the system, but maintenance on an OSHG system is not very demanding and includes daily or weekly reviews of the water softener, reviewing for leaks, changing filters, and acid cleaning of the electrolytic cell, the most critical part of the maintenance program. Acid cleaning is performed after a certain number of hours, determined by the application, the environment, and water and salt quality.

Are there OSHG systems on the market with features that impact maintenance?

Yes. Some OSHG systems come with a custom-designed acid cart. The cart is fully contained, minimizing exposure to harmful chemicals. Easy connections allow for fast, clean-in-place maintenance.

Built-in maintenance reminders on the system HMI touchscreen display can be very helpful in preventing missed maintenance by notifying operations when maintenance is due for proper scheduling.

Remote monitoring allows a user to access the screen from anywhere – on a computer or smart device, even a phone. You can simply sign in and check the current conditions of the system. With a remote monitoring feature, you can view, system parameters, tank levels and if the machine is in operation or standby mode.

On some OSHG systems, the electrodes are visible through either acrylic endcaps or acrylic casings, which offers the advantage of seeing the cell during maintenance checks.

Some systems offer efficiency savings. For example, split flow technology can provide lower operating temperatures and reduced salt and electricity consumption adding up to additional savings over the life of the system.