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

• Published in: Water science & technology. Water supply Vol. 23; no. 4; pp. 1587 - 1598
• Main Authors: Araya-Obando, José Andrés, Rietveld, Luuk C., Kelly-Coto, Daniel E., Quesada-González, Andrea, Caballero-Chavarría, Andrey, Romero-Esquivel, Luis G.
• Format: Journal Article
• Language: English
• Published: London IWA Publishing 01.04.2023
• Subjects: Adsorption; Biofilters; Biofiltration; Columns (structural); Drinking water; Experiments; Flow; flow-through; Groundwater; Inoculation; Limiting factors; Manganese; manganese-removal; Microorganisms; Oxidation; Pumice; pumice media; recirculating; Removal; Ripening; start-up; Startups; Velocity; Water consumption; Water depth; Water treatment
• ISSN: 1606-9749; 1607-0798
• DOI: 10.2166/ws.2023.045

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 < 0.1 mg·L−1) at 15 cm filter depth in 11 days. Recirculating filter columns required 32 days to reach compliance at 30 cm depth. The start-up in recirculation regime resulted in a water consumption reduction of about 50% compared with flow-through regime. The intermittent provision of the Mn-loading in recirculating regime impacted the Mn-oxidizing bacteria (MOB) concentration in the pumice stone medium. Both flow regimes required a similar total Mn-loading (0.16 and 0.11 kg·Mn·m−2, respectively), suggesting that Mn-loading was the limiting factor for the ripening of pumice.