Master of Science in Civil Engineering (MSCE)
Civil and Environmental Engineering
Static low density media (SLDM) filtration has been received with great admiration in the aquaculture industry and consequently spawned into the domestic wastewater setting on the pilot scale. This method of granular filtration uses plastic beads to facilitate the roles of both clarification and biofiltration into one compact unit. The fundamental operating principles utilized in this form of treatment can be greatly enhanced when they are coupled with self contained recirculation from airlift pumps. Recirculation of this type in a SLDM unit has the ability to provide multiple passes of the substrate in the wastewater through the bead bed to enhance removal efficiency. The main objective of this study was to determine the discharge and aeration properties associated with a 6” airlift pump when combined with a 25 ft3 SLDM filter. Data was collected using the SLDM filter and airlift pump configuration to determine the optimum submergence to lift ratio and air injection rate needed to achieve full benefit. It was determined that a submergence to lift ratio of 4 to 1 at an air injection rate between 15 to 25 cfm was the most desirable for the given application. This range of air injection equates to about 90 to 150 gpm of discharge respectively. This air injection range also provided approximately 2.00 to 3.00 Kg-O2 per day for heterotrophic decay and 1.50 to 2.25 Kg-O2 per day for nitrogenous decay in the filter respectively. In order to maximize the potential of the available bead volume in the given 25 ft3 SLDM filter, heterotrophic decomposition would require only one draft tube while nitrification would require four 6” airlift draft tubes for adequate recirculation.
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Johnson, Brian Sidney, "Airlift assisted wastewater treatment" (2008). LSU Master's Theses. 3509.