Faced with an increasing need to maintain carbon and carbon towers in a sanitary condition, the food and beverage industry requires a consistent, reliable sanitization method, and heat optimized technology (HOT) helps address this need. Carbon towers are very efficient in removing chlorine, chloramines and a wide range of organic contaminants.Yet, they are vulnerable to bacterial growth and organic fouling, and therefore require backwashing and periodic sanitization. When fed with surface waters, they also require steam stripping to remove accumulated volatiles such as trihalomethanes (THMs).
Explore this issueAugust/September 2005
HOT is a patented process used for sanitizing carbon towers to control bacterial growth and organic fouling. By combining the carbon tower’s backwash and sanitization steps with a recirculation process in one cohesive step, this technology greatly increases the effectiveness of the sanitization, while reducing water consumption. The fully automated HOT system operates in two modes:
- For daily or weekly backwashing: The tower is backwashed for five minutes with the water into the drain, removing sediments, contaminants and debris. This also expands the carbon bed, which is critical to avoid channeling.
Backwashing continues (back-flushing) in a recirculation mode through a filter to remove any fines. This allows a highly efficient backwash with a water savings of approximately 75 percent.
Valves automatically position themselves in the filter-to-waste position, and the system is ready for production.
- For weekly or scheduled sanitization: Exactly as above, but when the unit starts the recirculation (back-flushing mode), the heat exchanger is activated and the temperature is raised to 180º to 185º F. The entire sanitization process takes 65 minutes. A thorough bacteria “kill” is achieved, as the heating is accomplished while the carbon is fully expanded.
A complete HOT carbon filter system (Figure 1) consists of a carbon tower, heat exchanger, optional cooling heat exchanger, recirculation pump, cartridge filter and control panel. For both the backwashing mode and the periodic sanitization, a water savings of 75 percent is typical, along with savings in energy, manpower and time. During the sanitization process, no steam is in contact with the carbon bed.
Heat optimized technology has been proven in field studies to provide better microbial kill than conventional steaming because of the uniform heating of the carbon bed in the recirculating stage, and reduced potential for cold spots. conventional steaming and even steam stripping cannot maintain consistent heating because of the way steam is fed into the tower.
How often you need to sanitize your HOT carbon system depends on your feed water quality and your final water quality specification. Most HOT system installations are sanitized once a week as a safety precaution, with good results. When the HOT system is installed on a carbon tower that is located in the treatment chain after a reverse osmosis or nanofiltration membrane, sanitizing every two weeks has produced excellent results.