Manganese release linked to carbonate dissolution during the start-up phase of a subsurface iron removal well in Khabarovsk, Russia

• Published in: The Science of the total environment 2019-02, Vol.650 (Pt 2), p.1722-1733
• Main Authors: Paufler, S., Grischek, T., Herlitzius, J., Feller, J., Kulakov, V.V.
• Format: Article
• Language: English
• Subjects: Carbonate dissolution; Manganese release; Russia; Start-up phase; Subsurface iron removal
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.09.319

Subsurface iron removal (SIR) is a proven pre-treatment technology for removing dissolved iron and manganese from groundwater. The start-up phase of a SIR well and the proper development of the reaction zone around the well are crucial for its subsequent performance. This study evaluates the start-up phase of a SIR production well in Khabarovsk, Russia during the first 194 SIR cycles. A strong release of manganese was observed, which led to concentrations twice as high as the background value of the pristine groundwater. Regular monitoring of the production well and its three adjacent observation wells showed that iron removal began immediately after start-up and that the reaction zone was completely formed within 25 SIR cycles. Closed-bottle batch tests and a flow-through leaching test revealed that the grain size of the aquifer material and groundwater pH are the primary controls on manganese release. During infiltration phases the dissolution of manganese-bearing carbonate minerals was caused by direct oxidation by O2, whereas the low groundwater pH of 6 seemed to be responsible for the manganese release during extraction. [Display omitted] •An unexpected Mn release was observed during the start-up phase of a SIR well.•Water quality data of the first 194 infiltration & extraction phases were evaluated.•Column-experiments & closed-bottle batch tests with aquifer sediment were conducted.•Aquifer materials' grain size and groundwater pH primary controlled the Mn release.•Dissolution of Mn-bearing carbonate minerals was identified as primary Mn source.