Title: Use of Chlorine Dioxide to Control Biofouling in a Heat Transfer System
Learner Objectives:
This presentation will demonstrate the efficacy of using chlorine dioxide to mitigate biofouling in a heat transfer system.
Content/Topic Outline:
Presenter:
Dr. Dean Gregory. Bio is below.
Presentation Description:
Introduction. Controlling biofouling in heat transfer systems is critical for proper and safe operation of many industrial processes. Historically, the heat transfer system at a mold-production company (used to cool presses) had experienced excessive biomass accumulation despite the previous biocide regimen of hydrogen peroxide/DBNPA, which was deemed to be marginally effective. To mitigate the recurring biofouling issues, a trial was conducted using chlorine dioxide (ClO2), a well-documented biocide and stronger, in terms of microbial inactivation, than hydrogen peroxide/DBNPA. A proprietary and patented 0.3% aqueous chlorine dioxide solution was used in the trial (Solution 3000, CDG Environmental).
Chlorine dioxide solution and application. The 0.3% (3000 mg/L) aqueous ClO2 solution is ready-to-use and was pumped directly from its container (330-gallon tote) and into the hot well of the heat transfer system. The overall strategy was to use an initial high-concentration slug dose to establish a residual of approximately 5 mg/L, followed by low-concentration, intermittent dosing, the frequency of which would be dictated by preliminary results.
Prior to ClO2 addition, thick, black biomass would accumulate in the system, causing clogging of screens. This biomass proliferated despite the daily addition of 4 gallons of 35% hydrogen peroxide.
Initial ClO2 dosing. Initially, 160 gallons of chlorine dioxide solution were added to attain a ClO2 residual of 5 mg/L. Significant changes in the appearance and mass of the biofilm were observed. Compared to previous system flushes using 35 percent hydrogen peroxide, the biomass was less prevalent and a light brown color (compared to black).
Biomass and ATP reduction. In addition to the visual observations of the system, the reduction in biofilm growth was confirmed by weighing samples, at the same location and surface area over time. The addition of chlorine dioxide immediately brought a contamination event under control and reduced biofilm growth to near-zero levels in subsequent weeks. ATP levels ranged from 0- 100 RLU during the three-week period of the trial. An ATP measurement of less than 300 RLU in the heat transfer system is considered acceptable.
Conclusion. The application of a 0.3%, ready-to-use ClO2 solution significantly decreased biomass growth in all parts of the heat transfer system, increasing its efficiency and therefore the overall performance of the mold-production process. In addition, the need for physical cleanouts of the system has been significantly reduced. Chlorine dioxide has become the primary biocide and ATP results continue to illustrate effective microbial control.
Presenter Bio:
Dr. Dean Gregory received a PhD in Environmental Engineering from Colorado State University in 2003. Dr. Gregory has 25 years of experience in using chlorine dioxide for drinking and industrial water treatment applications. He is currently the Sr. Scientist for CDG Environmental and has been with the company since 2005. Dr. Gregory lives outside of Denver, Colorado.