Development of attapulgite composite ceramsite/quartz sand double-layer biofilter for micropolluted drinking source water purification

This study compared start-up and steady-state affecting factors of attapulgite composite ceramsite/quartz sand double-layer biofilter (ACC/QSDLBF) and quartz sand single-layer biofilter (QSSLBF) on micropolluted drinking source water treatment. Results showed that the ACC has suitable pore size distribution in the range of 5–850 nm which is conducive to biofiltration. Turbidity removal efficiency of ACC/QSDLBF was a little lower than QSSLBF, but organic matters and ammonia removal efficiencies of ACC/QSDLBF were much higher than QSSLBF due to biodegradation and nitrification by microorganisms colonizing on the ACC. At stable state, the growth of head loss for ACC/QSDLBF was lower than that of QSSLBF. The complete filtration cycle of ACC/QSDLBF was 52 h. The total COD_Mn removal rate of ACC/QSDLBF was 20.93 %, in which 90 % of removed total COD_Mn was achieved at the upper 60 cm of ACC filter layer. The removal of COD_Mn decreased from 35.89 to 13.16 % in ACC/QSDLBF when increasing hydraulic loading from 2 to 16 m/h. After analysis of efficient EBCT in ACC/QSDLBF, optimized hydraulic loading was 12 m/h. These conclusions would be helpful to practical application of ACC as functional material for new construction of waterworks, especially upgrading of existing waterworks treating micropolluted drinking source water.