Start-Up and Performance of a Full Scale Passive System In-Cluding Biofilters for the Treatment of Fe, as and Mn in a Neutral Mine Drainage

Passive mine drainage treatment plants are the scene of many chemical and biological reactions. Here, establishment iron (Fe), arsenic (As), manganese (Mn) removal was monitored immediately after commissioning Lopérec (Brittany, France) passive water plant, composed aeration cascades settling ponds followed by pozzolana biofilters. Iron As were almost completely removed commissioning, while Mn took more than 28 days to reach its maximum performance. Investigations performed during two periods presenting strong variations in feeding flow-rates: from 2.8 m3.h−1 8.6 13.2 31.3 m3.h−1. Design flow rate reached first week second period. Dissolved Fe not affected decrease residence time only slightly affected. Microbial communities biofilter presented similarities with those pond sludge, genera including Mn-oxidizing species detected. Proportion bacteria carrying aioA gene encoding for As(III)-oxidase enzyme increased Results suggest is mainly associated bio-oxidation whereas could be attributed oxidation precipitation Fe, possibly helped As(III) bio-oxidation.