Journal article
Control of biological growth in recirculating cooling systems using treated secondary effluent as makeup water with monochloramine
Water research (Oxford), Vol.46(19), pp.6508-6518
12/01/2012
Handle:
https://hdl.handle.net/2376/101788
PMID: 23063442
Abstract
Secondary-treated municipal wastewater, an abundant and widely distributed impaired water source, is a promising alternative water source for thermoelectric power plant cooling. However, excessive biological growth is a major challenge associated with wastewater reuse in cooling systems as it can interfere with normal system operation as well as enhance corrosion and scaling problems. Furthermore, possible emission of biological aerosols (e.g., Legionella pneumophila) with the cooling tower drift can lead to public health concerns within the zone of aerosol deposition. In this study, the effectiveness of pre-formed and in-situ-formed monochloramine was evaluated for its ability to control biological growth in recirculating cooling systems using secondary-treated municipal wastewater as the only makeup water source. Bench-scale studies were compared with pilot-scale studies for their ability to predict system behavior under realistic process conditions. Effectiveness of the continuous addition of pre-formed monochloramine and monochloramine formed in-situ through the reaction of free chlorine with ammonia in the incoming water was evaluated in terms of biocide residual and its ability to control both planktonic and sessile microbial populations. Results revealed that monochloramine can effectively control biofouling in cooling systems employing secondary-treated municipal wastewater and has advantages relative to use of free chlorine, but that bench-scale studies seriously underestimate biocide dose and residual requirements for proper control of biological growth in full-scale systems. Pre-formed monochloramine offered longer residence time and more reliable performance than in-situ-formed monochloramine due to highly variable ammonia concentration in the recirculating water caused by ammonia stripping in the cooling tower. Pilot-scale tests revealed that much lower dosing rate was required to maintain similar total chlorine residual when pre-formed monochloramine was used as compared to in-situ-formed monochloramine. Adjustment of biocide dose to maintain monochloramine residual above 3mg/L is needed to achieve successful biological growth control in recirculating cooling systems using secondary-treated municipal effluent as the only source of makeup water.
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► Biological growth control in concentrated secondary-treated municipal wastewater using chloramines. ► NH3 fluctuation due to air stripping effect critically affects in-situ NH2Cl formation. ► Preformed NH2Cl out-performed the in-situ-formed NH2Cl. ► Maintaining NH2Cl residual above 3 ppm yields excellent biological growth control. ► Use of NH2Cl in concentrated secondary-treated municipal wastewater prevents the presence of Legionella.
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Details
- Title
- Control of biological growth in recirculating cooling systems using treated secondary effluent as makeup water with monochloramine
- Creators
- Shih-Hsiang Chien - Department of Civil and Environmental Engineering, University of Pittsburgh, PA 15261, USAIndranil Chowdhury - Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92507, USAMing-Kai Hsieh - Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USAHeng Li - Department of Civil and Environmental Engineering, University of Pittsburgh, PA 15261, USADavid A Dzombak - Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USARadisav D Vidic - Department of Civil and Environmental Engineering, University of Pittsburgh, PA 15261, USA
- Publication Details
- Water research (Oxford), Vol.46(19), pp.6508-6518
- Academic Unit
- Civil and Environmental Engineering, Department of
- Publisher
- Elsevier Ltd
- Identifiers
- 99900546649901842
- Language
- English
- Resource Type
- Journal article