Reduction of Chlorine Disinfection Dosage through Optimal Jet Design in the Hong Kong Harbor Area Treatment Scheme
Publication: Journal of Environmental Engineering
Volume 149, Issue 2
Abstract
Chlorine is commonly used in disinfection processes in wastewater treatment plants. The chlorine solution is typically dosed by turbulent mixing through multiport jet diffusers. The chlorine reacts with the inorganic and organic nitrogenous compounds at a fast rate (in the order of 1 s or less), and a significant portion of the dosed chlorine can be rapidly consumed by the reactions instead of destroying the pathogens. Despite extensive previous research, the chlorine consumption in the complex sewage flow remains an elusive problem. Field-scale experiments have been carried out to study the chlorine consumption in the turbulent mixing of dense chlorine jets with the primary treated sewage effluent of the Stonecutter’s Island Sewage Treatment Works (serving a population of 5.7 million). Based on jet theory and the field tests, it is proposed to discharge the chlorine jets at a location of highest velocity to minimize the contact time of the sewage with high concentration chlorine. Full-scale in-plant experiments demonstrated that significant savings in chlorine can be achieved with optimal jet diffuser design and placement; at nominal applied chlorine dosages of 12 and in winter and summer, respectively, the chlorine demand can be reduced by up to 30% compared with the conventional dosing design. The relatively simple dosing reconfiguration results in significant savings in chlorine and energy, reduces harmful impact to the environment, and improves plant operation reliability. The chlorine demands from daily operations are well-correlated with the results of the field-scale models. Predictions of the chlorine demand as a function of applied dosage and temperature were obtained from the collective field data.
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Data Availability Statement
All the data that support the findings of this studying are available from the corresponding author upon reasonable request.
Acknowledgments
The support of the Hong Kong Research Grants Council (General Research Fund No. 16215618) is gratefully acknowledged. This work was also supported in part by the Drainage Services Department of the Hong Kong Special Administrative Region (HKSAR) Government (Contract HATS 02/2017).
References
Chan, S. N., Q. S. Qiao, J. H. W. Lee, K. W. Choi, and J.-C. Huang. 2017. “Modeling of mixing and rapid chlorine demand in sewage disinfection with dense chlorine jets.” J. Environ. Eng. 143 (11): 04017074. https://doi.org/10.1061/(ASCE)EE.1943-7870.0001274.
DSD (Drainage Services Department). 2019. “Harbour Area Treatment Scheme—A clean harbour for Hong Kong.” Accessed July 30, 2021. https://www.dsd.gov.hk/others/HATS2A/en/.
Lee, J. H. W., and V. H. Chu. 2003. Turbulent jets and plumes—A Lagrangian approach. Boston: Kulwer Academic Publishers.
Lee, J. H. W., J. C. Huang, D. K. W. Choi, S. N. Chan, and Q. S. Qiao. 2017a. Optimal operation plan for disinfection dosing. Hong Kong: Drainage Services Dept., Hong Kong Special Administrative Region Government.
Lee, J. H. W., Q. S. Qiao, S. N. Chan, K. W. Choi, and J.-C. Huang. 2017b. “Field experiments of chlorine demand in disinfection of treated primary effluent.” J. Environ. Eng. 143 (11): 04017073. https://doi.org/10.1061/(ASCE)EE.1943-7870.0001295.
Lee, J. H. W., Q. S. Qiao, D. K. W. Choi, and S. N. Chan. 2018. Pilot study on the feasibility of using two-point chlorine dosage for the disinfection facilities of the Harbour Area Treatment Scheme. Hong Kong: Drainage Services Dept., Hong Kong Special Administrative Region Government.
Li, W., X. Zhang, X. Li, and J. H. W. Lee. 2018. “Mystery of the high chlorine consumption in disinfecting a chemically enhanced primary saline sewage.” Water Res. 145 (Nov): 181–189. https://doi.org/10.1016/j.watres.2018.08.031.
Longley, K. E. 1978. “Turbulence factors in chlorine disinfection of wastewater.” Water Res. 12 (10): 813–822. https://doi.org/10.1016/0043-1354(78)90032-5.
Qiao, Q. S., K. W. Choi, S. N. Chan, and J. H. W. Lee. 2017. “Internal hydraulics of a chlorine jet diffuser.” J. Hydraul. Eng. 143 (12): 06017022. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001388.
Sepp, E., and G. C. White. 1981. Manual for wastewater chlorination and dechlorination practices. Sacramento, CA: State Water Resources Control Board.
Stover, E. L., C. N. Hass, K. L. Rakness, and O. K. Scheible. 1986. Design manual—Municipal wastewater disinfection. Washington, DC: USEPA.
White, G. C. 1974. “Disinfection practices in the San Francisco Bay area.” J. Water Pollut. Control Fed. 46 (1): 89–101.
Yang, A. J. K., S. N. Chan, and J. H. W. Lee. 2019. “Integral model of a reacting chlorine jet in ammonia nitrogen and treated primary effluent.” J. Hydro-Environ. Res. 27 (Dec): 50–64. https://doi.org/10.1016/j.jher.2019.08.004.
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© 2022 American Society of Civil Engineers.
History
Received: Jan 16, 2022
Accepted: Sep 7, 2022
Published online: Nov 22, 2022
Published in print: Feb 1, 2023
Discussion open until: Apr 22, 2023
ASCE Technical Topics:
- Chemical compounds
- Chemical elements
- Chemicals
- Chemistry
- Chlorine
- Diffusion
- Disinfection
- Engineering fundamentals
- Engineering mechanics
- Environmental engineering
- Field tests
- Flow (fluid dynamics)
- Fluid dynamics
- Fluid mechanics
- Hydraulic engineering
- Hydraulic structures
- Hydrologic engineering
- Municipal wastes
- Pollutants
- Ports and harbors
- Sewage
- Tests (by type)
- Thermodynamics
- Transport phenomena
- Turbulent flow
- Wastes
- Wastewater treatment plants
- Water and water resources
- Water treatment
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