Pitt Logo LinkContact Us

Biological Control in Cooling Water Systems Using Non-Chemical Water Treatment Devices

Duda, Scott (2011) Biological Control in Cooling Water Systems Using Non-Chemical Water Treatment Devices. Master's Thesis, University of Pittsburgh.

[img]
Preview
PDF - Primary Text
Download (18Mb) | Preview

    Abstract

    Microbial growth in cooling water systems causes corrosion, decreases energy efficiency, and has the potential to cause human infection. Control of microbial growth in these systems is typically achieved using chemical biocides. Recently, non-chemical water treatment methods have seen increased use as an alternative. However, few objective studies with an untreated system as a reference are available to verify the efficacy of these devices to control microbial growth in cooling towers. The specific objective of this investigation was to provide a controlled, independent, and scientific evaluation of several classes of non-chemical treatment devices (NCDs) for controlling biological activity in a model cooling tower system.Five NCDs were evaluated for efficacy in reducing planktonic and sessile microbial populations within a pilot-scale cooling system. The treatment mechanisms included magnetic, pulsed electric field, electrostatic, ultrasonic, and hydrodynamic cavitation. Two model towers were designed and operated to simulate field conditions. One tower served as the untreated control (T1) while the NCD was installed on the second tower (T2). Each device trial was conducted over a 4-week period. Heterotrophic plate counts (HPC) were used to monitor planktonic and sessile biological growth. Physicochemical monitoring included temperature, conductivity, pH, alkalinity, hardness, total dissolved solids (TDS), ORP, and chloride. Make-up water for each system was dechlorinated city tap water. According to information documented in the literature, the makeup water chemistry used in this study is representative of that found in many building cooling tower systems.Under the experimental conditions used in this study, no statistically significant difference in planktonic and sessile microbial concentrations (HPC) was observed between the control tower and a tower treated by any of the five NCDs evaluated in this study. Standard chemical treatment of pilot-scale cooling towers by the addition of free chlorine (positive control) was able to achieve appreciable reduction in both planktonic and sessile microbial growth in these towers. These positive controls were repeated three times throughout the study and the results clearly showed that free chlorine was able to control biological growth in every instance, even after heavy microbial colonization of model cooling towers.


    Share

    Citation/Export:
    Social Networking:

    Details

    Item Type: University of Pittsburgh ETD
    ETD Committee:
    ETD Committee TypeCommittee MemberEmail
    Committee ChairVidic, Radisavvidic@pitt.edu
    Committee MemberStout, Janetjstout@specialpathogenslab.com
    Committee MemberCasson, Leonardcasson@pitt.edu
    Title: Biological Control in Cooling Water Systems Using Non-Chemical Water Treatment Devices
    Status: Unpublished
    Abstract: Microbial growth in cooling water systems causes corrosion, decreases energy efficiency, and has the potential to cause human infection. Control of microbial growth in these systems is typically achieved using chemical biocides. Recently, non-chemical water treatment methods have seen increased use as an alternative. However, few objective studies with an untreated system as a reference are available to verify the efficacy of these devices to control microbial growth in cooling towers. The specific objective of this investigation was to provide a controlled, independent, and scientific evaluation of several classes of non-chemical treatment devices (NCDs) for controlling biological activity in a model cooling tower system.Five NCDs were evaluated for efficacy in reducing planktonic and sessile microbial populations within a pilot-scale cooling system. The treatment mechanisms included magnetic, pulsed electric field, electrostatic, ultrasonic, and hydrodynamic cavitation. Two model towers were designed and operated to simulate field conditions. One tower served as the untreated control (T1) while the NCD was installed on the second tower (T2). Each device trial was conducted over a 4-week period. Heterotrophic plate counts (HPC) were used to monitor planktonic and sessile biological growth. Physicochemical monitoring included temperature, conductivity, pH, alkalinity, hardness, total dissolved solids (TDS), ORP, and chloride. Make-up water for each system was dechlorinated city tap water. According to information documented in the literature, the makeup water chemistry used in this study is representative of that found in many building cooling tower systems.Under the experimental conditions used in this study, no statistically significant difference in planktonic and sessile microbial concentrations (HPC) was observed between the control tower and a tower treated by any of the five NCDs evaluated in this study. Standard chemical treatment of pilot-scale cooling towers by the addition of free chlorine (positive control) was able to achieve appreciable reduction in both planktonic and sessile microbial growth in these towers. These positive controls were repeated three times throughout the study and the results clearly showed that free chlorine was able to control biological growth in every instance, even after heavy microbial colonization of model cooling towers.
    Date: 26 January 2011
    Date Type: Completion
    Defense Date: 22 March 2010
    Approval Date: 26 January 2011
    Submission Date: 12 November 2010
    Access Restriction: No restriction; The work is available for access worldwide immediately.
    Patent pending: No
    Institution: University of Pittsburgh
    Thesis Type: Master's Thesis
    Refereed: Yes
    Degree: MSCE - Master of Science in Civil Engineering
    URN: etd-11122010-134752
    Uncontrolled Keywords: Cooling Tower; Heterotrophic Plate Count Bacteria; Non-chemical Water Treatment; Physical Water Treatment; Water Treatment
    Schools and Programs: Swanson School of Engineering > Civil and Environmental Engineering
    Date Deposited: 10 Nov 2011 15:04
    Last Modified: 11 May 2012 12:51
    Other ID: http://etd.library.pitt.edu/ETD/available/etd-11122010-134752/, etd-11122010-134752

    Actions (login required)

    View Item

    Document Downloads