Opitz, J., M. Alte, M. Bauer, and S. Peiffer.
International Mine Water Association (IMWA) Conference, 15-19 July, Perm, Russia, 2019

A passive treatment pilot plant was implemented at an abandoned, open-pit lignite mine site to investigate the suitability of serially connected settling ponds, wetlands and sediment filters for passive iron removal capable of reaching a 1 mg/L compliance limit. The system was designed to collect comparable hydraulic and hydrochemical data to investigate performance, kinetic relationships, and critical influencing factors as a basis for upscaling. After demonstrating reproducibility at equal flow rates in 3 identical lines, hydraulic variation was used to develop comparison data for sizing a full-scale passive system. The multi-stage setup was successful in reducing iron concentrations of 10 mg/L to the 1 mg/L goal. Area-adjusted removal rates were relatively low due to low hydraulic loading. Dependence of both treatment efficiency and area-adjusted removal on hydraulic loading was demonstrated during the variation period, showing direct and inverse relationships at graded flow rates, respectively. Future work will include further variation periods with intermediate, higher and lower flow rates to expand the database and the generation of high-resolution mass balances using continuously monitored turbidity as a proxy for (particulate) iron in the pilot plant to design a full-scale system. https://www.imwa.info/docs/imwa_2019/IMWA2019_Opitz_256.pdf