Impact of filter media on the performance of full-scale recirculating biofilters for treating multi-residential wastewater

The main objective of this paper was to evaluate the effectiveness of silica sand, crushed glass, peat, and geotextile as a medium in RBFs in the removal for organic matter, nutrients and bacteria from domestic wastewater based on a field-scale study. In particular, this field-scale study was conducted to treat domestic wastewater from a small community of 10 households from the Municipality of Lunenburg, Nova Scotia, Canada. The average influent 5 d biochemical oxygen demand (BOD5) and total suspended solids (TSS) concentrations into the field filter system were 381±64 (mean±standard deviation) and 46±21 mg/L, respectively. The results showed that crushed glass could be an effective medium in RBFs since the crushed glass filter produced stable effluent BOD5 and TSS concentrations of less than 20 mg/L. Geotextile was found to be another successful alternative filter medium with the effluent BOD5 and TSS of 18±11 and 11±7 mg/L, respectively, even though the porosity of geotexitle filter was as high as 0.90. Peat was not able to provide efficient performance due to its poor BOD5 and NH4+-N removals. This study measured the water quality variation at different components of the RBFs. The results of this study showed that the recirculation tank was the main facilitator of the denitrification process. In addition, this study found that RBFs could efficiently treat domestic wastewater for BOD5 removal under the organic loading rates as high as 0.070 kg/m2/d.