Increasing Plant Capacity By Optimizing Filter Media Design: The Atlantic CityMUA Experience

摘要

A pilot study was conducted to evaluate the Atlantic CityMunicipal Utilities Authority’s (ACMUA) existing filtration facilities todetermine the potential for increasing filtration capacity. The ACMUA hasestablished a goal of upgrading their filtration facilities to allow for: 1)additional capacity (increase from 18 MGD to 22 MGD); 2) the ability toremove filters from service to perform maintenance; and 3) to meet a turbiditygoal of 0.1 NTU at their Filtration Plant.Filtration theory, particularly the L/d (bed depth divided by the media diameter)and L/d3 ratios, was examined in order to design alternative filter mediaconfigurations. Traditionally, the L/d ratio has been on the order of 1,000 to1,200. Recent filtration theory has shown particle removal is a function of theL/d3 ratio which is more dependent on media size (ES). The higher the L/d3ratio the lower the initial filtered water turbidity.The pilot study tested three alternative media configurations along with a controlcolumn that was identical to the existing filter media configuration;? Control: 36” Filtrasorb 300 (0.9 mm ES) and 4” sand (0.5 mm ES)? Alternative 1: 36” Filtrasorb 300 (0.9 mm ES) and 12” sand (0.5 mmES)? Alternative 2: 48” Filtrasorb 816 (1.4 mm ES) and 12” sand (0.5 mmES)? Alternative 3: 48” Filtrasorb 820 (1.1 mm ES) and 12” sand (0.5 mmES)The three alternative media configurations and the control were tested at aloading rate of 5.5 gpm/sf. The tests were conducted with four 4-inch diameterfiltration columns operating in parallel. The flow treated by the filtrationcolumns was taken from the top of the existing filters. Data recorded includedturbidity, particle counts and headloss.The control filter column mimicked the full-scale plant. All three alternativeconfigurations outperformed the control filter – that is, they produced filteredwater with lower turbidity and particle counts, but longer filter run times.The pilot study results demonstrated that additional capacity could be achievedwithout constructing new filtration facilities. Renovation of the existing filerssaved ACMUA millions of dollars in capital costs. The design of the upgrade ofthe existing filters was based on the configuration of the pilot filter system withthe optimum filtered water turbidity, particle count and unit filter run volumes.The selected media configuration was 36 inches of 1.1 mm ES GAC over 12inches of 0.5 mm ES sand. The new filters have a higher L/d3 ratio, thicker sandlayer, new underdrain and upgrade in the backwash scheme including air scourand increased backwash rate. The first of six filter upgrades was placed inservice in March 2007.