Study of biological up-flow roughing filters designed for drinking water pretreatment in rural areas: using ceramic media as filter material

Roughing filters have been successfully employed as a pretreatment method in rural water supply, but few studies have reported the performance of up-flow roughing filters (URFs) packed with ceramic media. In this study, two pilot-scale URFs filled with ceramic media were designed. Filter performance, height profiles and head loss development were fully investigated. The average DOC, UV254 absorbance, NH4+-N and total bacterial counts removal efficiencies of filters were found to be close to 8%, 10%, 70% and 0.6 log (75%), respectively. Both filters could remove about 60–90% of turbidity with influent turbidity ranging from 1 to 500 NTU and high removal efficiencies (∼60%) were achieved when influent turbidity was lower than 2.5 NTU at a hydraulic load up to 2 m h−1. Height profiles revealed that UV254 absorbance, NH4+-N and turbidity were primarily removed in the former part of filter columns and that the separated solids stored within 20 cm of ceramic media layer above the bottom contributed to over 90% of total head loss. Filter run times were estimated to be around 60–80 days with a maximum head loss of 30 cm and an average influent turbidity of 10 NTU. The results indicated that the two URFs, combining low-cost operation and simple maintenance with good performance, were well suited to small waterworks in rural areas.