AWWA ACE61785

AWWA ACE61785 Using Simple, Cost-Effective Filter Evaluation Techniques to Optimize Filter Performance and Operation
Conference Proceeding by American Water Works Association, 06/17/2005

Huey, Bryan; Rennecker, J.L.; Crozes, Gil; Ardizzone, Robert A.

More info

Full Description

The purpose of this study was to evaluate the condition of the existing Alfred Merritt Smith Water Treatment Facility (AMSWTF) filters. AMSWTF is a 600million gallon per day (mgd) (2,270 Megaliters per day) direct filtration treatment plant, utilizingozone oxidation as the primary disinfectant and free chlorine for secondary distribution systemdisinfection. Due to the declining level and deteriorating water quality in Lake Mead, the plant'ssole raw water source, the AMSWTF has recently experienced shortened filter runs. Althoughthe recent lowering of the plant intake has improved the raw water quality, reducing the influentturbidity, particle counts and temperature back into historical ranges, lake levels are predicted tocontinue dropping. Evaluation of the filters is the first step in preparing the plant for futuredeclines in water quality.The evaluation process included a review of the filter and backwash operations, as well as anassessment of the filter media characteristics. Four filters each from Phases I and II and twofilters from Phase III were chosen for evaluation. Individual filters were selected with input fromthe plant operators and staff based on their observation of shorter filter runs, higher effluentturbidity, early particle break through and suspected media and support media upset. The majorunit processes at AMSWTF, and the three filter complexes that make up the filtration process areshown in relation to the rest of the facility, while the individual filters chosen forevaluation are presented in a simplified plant schematic. Filter data from all threephases of construction were reviewed including an assessment of the filter and backwashoperations. In addition, an assessment of the filter media characteristics was performed whichincluded filter bed core sampling, sieve analysis, floc retention profile analysis, spent filter washwater turbidity profiling, filter excavation and gravel bed profiling. Data taken from FilterNo. 15 constructed during Phase II in 1982 was chosen for this study. Includes figures.