Evaluation of Static Low Density Media Filters for Use in Domestic Wastewater Treatment
Static Low Density Media (SLDM) filters are submerged granular medium filters that contain a static matrix of floating media. These filters provide concurrent biological and physical treatment, and are therefore classified as bioclarifiers. Through different design and operation strategies, SLDM filters may be used for a variety of functions such as: solid-liquid separation alone, organic conversion and solids capture, nitrification and solids capture, and denitrification and solids capture. For operation as an aerobic unit, an external aeration strategy was developed to preserve the static nature of the bed.
In this study, SLDM filters treated a highly variable flow domestic wastewater generated from an industrial facility in Denham Springs, Louisiana. Various bench scale filter configurations were evaluated on their ability to perform both biological and physical treatment at a variety of hydraulic filtration rates, backwash frequencies, and configurations, while constantly keeping the filter bed in an aerobic state. Data collected from units recirculated via airlift pumps is reported. The pneumatically washed units in this study employed a modified shape media and a high backwashing frequency to enhance biofiltration capacities. Units were fed primary domestic wastewater effluents with mean CBOD5 (carbonaceous biochemical oxygen demand) of 100 and 150 mg/L. Mean influent TSS (total suspended solids) values for the two units tested were 60 and 90 mg/L. The airlift/SLDM filter combination was able to maintain mean hydraulic filtration rates in the range of 10-15 m/hr.
Findings indicate the unit is capable of producing CBOD5 and TSS effluent qualities in the 10-20 mg/l range when subject to organic loadings between 1 and 3.5 kg/m3.day. These values are higher than reported loading capacities for conventional secondary wastewater treatment strategies, such as Activated Sludge units, Trickling Filters, and Biological Aerated Filters. In this study, effluent CBOD5 levels were closely correlated with effluent TSS levels. Although no problems with media caking were observed, at times poor backwash interval selection did lead to severe oxygen depression within the bead bed. It is concluded that SLDM show promise for application in the domestic wastewater arena, particularly where the scale of the operation places a premium on simple operation.
Advisor:Ronald Malone; Kelly Rusch; John Pardue
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Keywords:civil environmental engineering
Date of Publication:11/14/2003