AWWA WQTC55181

The optimization of conditions used to operate full-scale ozone contactors is important in order to maximize disinfection efficiency against Cryptosporidium parvum oocysts while minimizing the formation of disinfection byproducts (DBP), particularly bromate. A direct approach to optimize contactor performance would be to measure both bromate concentrations and densities of viable C. parvum oocysts of the effluent under a variety of operating conditions. Unfortunately, although bromate analysis can be performed easily, the quantification of viable C. parvum oocysts is not currently feasible due to the low concentration at which they usually occur in nature. Instead, the most common approach to assess disinfection efficiency is the CT (product of disinfectant concentration and contact time) approach. Nevertheless, this approach may have severe limitations and uncertainties, due to the occurrence of non-ideal hydrodynamics, e.g. back-mixing and short-circuiting, within the reactor. An alternative approach is the use of fluorescent-dyed microspheres as non-biological surrogates. The main concept behind this approach is the fact that the microsphere, once introduced into a full-scale contactor, would experience the same hydrodynamic non-idealities and exposure to the disinfectant as those experienced by the microorganisms. The fluorescence intensity of the microsphere would decrease as a result of the reaction of the fluorescent dye with ozone, and this loss of fluorescence can then be correlated to the inactivation kinetics of C. parvum. The objective of this study is to investigate the use of fluorescent-dyed polystyrene microspheres as a tool to optimize the operating conditions that would result in maximum inactivation of C. parvum with minimum formation of bromate. The correlation developed between bench-scale experiments and the preliminary results obtained for full-scale demonstration tests are presented in this paper. Includes 8 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

01/01/2001

Number of Pages:

11

File Size:

1 file , 250 KB