Impact of the Daily Stratification/Destratification Cycle on Maturation Pond Disinfection Efficiency: A Numerical and Field Stud
N. W. Dahl1, C. J. Lemckert1,2,*, P.L. Woodfield1, H. M. Stratton1,3, A. Roiko1,4
1 School of Engineering, Griffith University, Gold Coast, Queensland, Australia 2 Smart Water Research Centre, Griffith University, Queensland, Australia 3 School of Natural Sciences, Griffith University, Gold Coast, Queensland, Australia 4 School of Medicine, Griffith University, Gold Coast, Queensland, Australia
(free)
Maturation ponds are commonly used as low energy, low cost disinfection systems as part of a more complex treatment plant. In this study, field measurements were compared to a onedimensional numerical model to investigate the thermal behaviour and die-off of E. coli and enterococci in a sub-tropical maturation pond. The pond stratified during the day and destratified during the night. This cyclic process (also observed in arid and tropical regions) has a marked impact on the movement of the pathogens through the pond and hence disinfection potential. The model simulated the stratification and destratification and showed that the concentration (representative of E. coli and enterococci) movement is limited by the thermocline and sunlight disinfection occurs above this point. The modelled die-off showed reasonable agreement with the field measurements when considering the exclusion of an exogenous inactivation mechanism and dark die-off. Destratification mixes the water column and the outlet concentration increases compared to the daytime concentration as a result.
