AWWA WQTC58953

AWWA WQTC58953 Application of the Integrated Disinfection Design Framework (IDDF) for Disinfection Contactors Performance Evaluation
Conference Proceeding by American Water Works Association, 11/02/2003

Barbeau, Benoit; El-Baz, Geraldine; Sarrazin, Virginia; Desjardins, Raymond

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The disinfectant dose (CT) is a key parameter to evaluate disinfection treatment efficiency. TheCTsub10/sub calculation is the simplest way to obtain a proxy to control disinfection processes. However,as the CTsub10/sub value calculated for regulation purposes appears to be very conservative, othermethods were proposed to evaluate more accurately the effective microbiological dose.Currently, the Integrated Disinfection Design Framework (IDDF) is the most complete approachproposed (Bellamy et al., 1998) and is based on combining a disinfectant decay model with amodel describing the contactor's hydraulic efficiency. This approach necessitates the completionof tracer and disinfectant decay studies in order to develop these models. While such tasks arerelatively simple to conduct for chlorine or chlorine dioxide contactors, their completions aremore difficult on ozone contactors due to the increased complexity of performing hydraulictracer tests on this unit process, and the variability of ozone residual within the ozonecontactors, especially in the first cell of contactors using bubble diffusers.The main objective of this project is to apply the IDDF methodology to two full-scale ozonefacilities in the Region of Montreal (Canada) in order to compare the resulting CT values withthose obtained by calculations (CT10). The study was performed on two water treatment plants(WTP) of the Quebec province: the Chomedey WTP (180 MLD) and the DesBaillets WTP(1,500 MLD) which supplies respectively the cities of Laval and Montreal. Both WTPs utilizepost-ozonation (after filtration). Due to the highquality water at Montreal WTP (originating from the St. Lawrence river), the applied ozonedosages are lower than at Laval WTP (1.2 vs 1.7 mg/L). The Montreal WTP is also designed withshorter contact times than in Laval (4.7 vs 13.8 min), which explains the lowerapplied ozone dosages at this plant. The Laval WTP relies on an ozone injection strategy forwhich 85% of the ozone dosage is applied in the first cell, while the remaining 15% is injected inthe second cell. In Montreal, the entire dose is injected in the first cell. Includes 7 references, tables, figures.