AWWA ACE95041

This paper presents the results from a 10 month long demonstration plant study for the Massachusetts Water ResourcesAuthority's Wachusett Reservoir supply. Previous pilot studies indicated the suitability of dissolved air flotation (DAF) for clarification of the surface supply. Upon further examination, it was speculated that the high quality of the raw water would lend itself to the use of lower flocculation times, higher basin loading rates, and ultimately, a more cost effective plant than indicated by the previous studies. A pilot testing program was undertaken to further optimize the DAF process, as well as to demonstrate the performance of the process to continuously meet all water quality objectives under all seasonal conditions. Optimization studies focused on two variables within the DAF process: reduced flocculation times ahead of DAF and increased DAF loading rates. Flocculation times of 5 to 15 minutes were investigated. DAF loading rates from 6 to 10 gpm/sf were evaluated. Results are presented for the following water quality and operational parameters: floated water turbidity, filtered water turbidity, filtered water particle counts, disinfection byproducts removal, and unit filter run volume.