Master of Science in Civil Engineering (MSCE)


Civil and Environmental Engineering

Document Type



Static Low Density Media filters have been used over the past two decades for nitrification and solids removal in high-density recirculating aquaculture systems. The SLDM filters are submerged biofilters which contain a plastic media with a density less than that of water. The media beds remain packed, or static, during operation except for periodic expansion of the bead bed during a backwash. More recently SLDM filters have been evaluated for secondary clarification of domestic wastewater where concurrent biological treatment and particulate removal occur within one unit. Recirculation is accomplished using airlifts which provide external aeration coupled with multiple pass removal of CBOD5 and TSS enhancing biofiltration performance. The following field study investigated the impact of filter media characteristics on the performance of SLDM filters in addition to an evaluation of their practical applications. Data from bench scale SLDM filters identical in configuration, but employing different media are reported. The media used were a boat-shaped (EN) media and a cylindrical KMT (Kaldness carrier) media. The units were fed effluent from a primary clarifier with a mean CBOD5 concentration of 104 mg/l and TSS concentration of 77 mg/l. Results indicate over 90% reduction in CBOD5 and TSS when subjected to an organic loading range between 1-2 kg/ using EN media. Over an 80 % reduction in CBOD5 and TSS levels were achieved using the SLDM unit with KMT media at the same organic loading range. Findings also indicated a significantly higher mean oxygen uptake rate of 1.8 kg/ for the EN media, which was twice that of the KMT media. Data are also reported from a study where multiple SLDM configurations were used for domestic wastewater treatment. Each application was unique in regards to the treatment objective. Removal of CBOD5, TSS, and TAN were achieved with the placement of each experimental unit within the treatment train. SLDM filters can be applied successfully for treatment of domestic wastewater. Proper media selection in conjunction with operating techniques can enhance performance of the filter. Specialized treatment is accomplished to meet objectives with a general hull design. The simple operation of SLDM filters using the external aeration strategy is a robust treatment alternative and particularly well suited for applications where space or service opportunities are limited.



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Committee Chair

Ronald F. Malone