Start-up of non-bioaugmented pumice biofilters in flow-through and recirculating flow regime for Mn removal

Abstract

Biofilters are effectively used for drinking water treatment. However, the long ripening time of virgin media for manganese (Mn) removal is a major concern. In this study, the influence of the flow regime on the ripening time of virgin pumice medium was investigated. For this purpose, pilot-scale experiments were performed to compare the start-up of flow-through and recirculating filter columns using inherent inoculation with the same groundwater source. The systems were operated at 2 m·h−1 with gradual flow increments up to 5 m·h−1 and avoiding Fe-loading. Effective Mn removal (>90%) in flow-through and recirculating columns was achieved after 8 and 23 days, respectively. Flow-through columns reached compliance with a local drinking water criterion (Mn 90%) in only 8 days.; Recirculating flow regime required 23 days, however, with 50% less water consumption.; Both flow regimes registered a similar total Mn-loading (0.11–0.16 kg·Mn·m−2).; Intermittent Mn-loading provision impacted the Mn-oxidizing bacteria concentration in the pumice stone medium.; Mn-loading was the limiting factor for the ripening of pumice stone medium.;

Keywords

• flow-through
• groundwater
• manganese-removal
• pumice media
• recirculating
• start-up