Formation of Trihalomethanes during Seawater Chlorination
ABSTRACT
The use of seawater for industrial cooling is a vital technology that poses some of the most profound environmental impact on the water quality in the Arabian Gulf. Biocide (chlorine) is added to the seawater to control biofouling of the cooling system. This added chlorine reacts with bromide and other chemicals naturally exist in the water to form a wide range of oxidants. Regrettably, reactions between the residual oxidants and natural organic matter in the water lead to formation of toxic halogenated organic compounds that have detrimental effects on the environment when they are discharged into the Gulf. This paper describes the formation of trihalomethanes (THMs) in seawater cooling systems. Results of kinetic experiments have shown that concentrations of THMs increased rapidly with time during the first half hour. Chlorination of seawater has shown significant increase in total THMs (TTHMs) and in bromoform concentrations. Rapid decrease of UV absorbance at 254 nm was also observed during seawater chlorination which is indicative of natural organic matter degradation into small organic molecules including THMs and other by-products. The increase in chlorine dose was accompanied with an increase in TTHMs and bromoform concentrations. Linear relationships between total chlorine concentration and both final TTHMs and bromoform concentrations were established. First order exponential decay and exponential associate functions were developed to correlate chlorine dose with formed THMs.
The use of seawater for industrial cooling is a vital technology that poses some of the most profound environmental impact on the water quality in the Arabian Gulf. Biocide (chlorine) is added to the seawater to control biofouling of the cooling system. This added chlorine reacts with bromide and other chemicals naturally exist in the water to form a wide range of oxidants. Regrettably, reactions between the residual oxidants and natural organic matter in the water lead to formation of toxic halogenated organic compounds that have detrimental effects on the environment when they are discharged into the Gulf. This paper describes the formation of trihalomethanes (THMs) in seawater cooling systems. Results of kinetic experiments have shown that concentrations of THMs increased rapidly with time during the first half hour. Chlorination of seawater has shown significant increase in total THMs (TTHMs) and in bromoform concentrations. Rapid decrease of UV absorbance at 254 nm was also observed during seawater chlorination which is indicative of natural organic matter degradation into small organic molecules including THMs and other by-products. The increase in chlorine dose was accompanied with an increase in TTHMs and bromoform concentrations. Linear relationships between total chlorine concentration and both final TTHMs and bromoform concentrations were established. First order exponential decay and exponential associate functions were developed to correlate chlorine dose with formed THMs.
Cite this paper
nullA. Abdel-Wahab, A. Khodary and N. Bensalah, "Formation of Trihalomethanes during Seawater Chlorination," Journal of Environmental Protection, Vol. 1 No. 4, 2010, pp. 456-465. doi: 10.4236/jep.2010.14053.
nullA. Abdel-Wahab, A. Khodary and N. Bensalah, "Formation of Trihalomethanes during Seawater Chlorination," Journal of Environmental Protection, Vol. 1 No. 4, 2010, pp. 456-465. doi: 10.4236/jep.2010.14053.
References
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[1] E. Agus, N. Voutchkov, D. L. Sedlak, “Disinfection By- products and Their Potential Impact on the Quality of Water Produced by Desalination Systems: A Literature Review,” Desalination, Vol. 237, No. 54, 2009, pp. 214- 237. [2] A. M. Shams El Din, A. A. Rasheed and A. A. Hammoud, “A Contribution to the Problem of Trihalomethane Formation from the Arabian Gulf Water,” Desalination, Vol. 85, No. 1, pp. 13-32. [3] M. Ali and P. Riley, “The Distribution of Halomethanes in the Coastal Waters of Kuwait,” Marine Pollution Bulletin, Vol. 17, No. 9, 1986, pp. 409-414. [4] B. Batchelor, “A Kinetic Model for Formation of Disinfection By-Products,” Fellowship Report, American Aca- demy for the Advancement of Science/Environmental Protection Agency Fellowship Program, Washington, DC, 1989. [5] W. R. Haag and M. H. Lietzke, “A Kinetic Model for Predicting the Concentrations of Active Halogens Species in Chlorinated Saline Cooling Waters: A Final Report,” ORNL/TM-7942, Oak Ridge National, 1981. [6] J. D. Johnson, G.W. Inman and T. W. Trofe, “Cooling Water Chlorination: The Kinetics of Chlorine, Bromine, and Ammonia in Sea Water,” NUREG/CR-1522 RE, Office of Nuclear Regulatory Research, U. S. Nuclear Regulatory Commission, Washington, DC, 1982. [7] J. D. Johnson and R. Overby, “Bromine and Bromamine Disinfection Chemistry,” Journal of Sanitary Energy Division, Vol. 97, No. 5, 1971, pp. 617-628. [8] M. J. Rodriguez, J. B. Serodes, P. Levallois and F. Proulx, “Chlorinated Disinfection By-Products in Drinking Water According to Source, Treatment, Season, and Distribution Location,” Journal of Environmental Engineering Science, Vol. 6, No. 4, 2007, pp. 355-365. [9] USEPA, “Stage 2 Disinfectants and Disinfection Byproducts Rule,” 2006. [10] P. D. Goodman, “Effect of Chlorine on Materials for Sea Water Cooling Systems: A Review of Chemical Reactions,” British Corrosion Journal, Vol. 70, No. 11, 1987, pp. 56-62. [11] APHA, AWWA and WET, “Standard Methods for the Examination of Water and Wastewaters” 21st Edition, Washington, DC, 2005. [12] M. Fabbricino and G. V. Korshin, “Formation of Disinfection By-Products and Applicability of Differential Absorbance Spectroscopy to Monitor Halogenation in Chlorinated Coastal and Deep Ocean Seawater,” Vol. 176, No. 1-3, 2005, pp. 57-69. [13] M. N. Fayad and S. Iqbal, “Chlorination Byproducts of Arabian Gulf Seawater,” Bulletin of Environmental Contamination and Toxicology, Vol. 38, No. 3, 1987, pp. 475-482. [14] G. L. Amy, P. A. Chadik and Z. K. Chowdhury, “Developing Models for Predicting Trihalomethane Formation Potential and Kinetics,” Journal of American Water Works Association, Vol. 79, No. 7, 1987, pp. 89-97. [15] D. Gang, T. E. Clevenger and S. K. Banerji, “Relationship of Chlorine Decay and THMs Formation to NOM size” Journal of Hazardous Materials, Vol. 96, No. 1, 2003, pp. 1-12. [16] B. A. Engerholm and G. L. Amy, “A predictive Model for Chloroform Formation from Humic Acid,” Journal of American Water Works Association, Vol. 75, No. 8, 1983, pp. 418-423; “chlorinated coastal and deep ocean seawater” Desalination, Vol. 176, No. 1-3, 2005, pp. 57-69. [17] E. E. Chang, P. C. Chiang, S. H. Chao and Y. L. Lin, “Relationship between Chlorine Consumption and Chlorination By-Products Formation for Model Compounds,” Chemosphere, Vol. 64, No. 7, 2006, pp. 1196- 1203. [18] J. Sohn, G. Amy, J. Choc, Y. Leed and Y. Yoon, “Disinfectant Decay and Disinfection By-Products Formation Model Development: Chlorination and Ozonation By- Products,” Water Research, Vol. 38, No. 10, 2004, pp. 2461-2478. [19] C. N. Hass and S. M. Karra, “Kinetics of Wastewater Chlorine Demand Exertion,” Journal of Water Pollution Control Federation, Vol. 56, No. 2, pp. 170-173. [20] AWWARF, “Maintaining Distribution System Residuals through Booster Chlorination,” AWWA Research Foundation, Denver, 2003.