Quantifying iron removal efficiency of a passive mine water treatment system using turbidity as a proxy for (particulate) iron

The Role of Macrophytes in Constructed Surface-flow Wetlands for Mine Water Treatment: A Review

“…Total suspended solids (TSS) content in wetland outflows can also display considerable seasonal patterns, with increased effluent TSS during the growing season due to generation of particulate NOM by vegetation growth and decay (Kadlec et al 2000). Regarding mine water treatment wetlands, it is important to note that increased effluent TSS in summer predominantly concerns wetland-derived particulate matter (i.e., the "natural background"; Gearheart 1992), whereas effluent suspended hydrous ferric oxides are expected to decrease with vegetation development (filtration) and NOM generation during the growing season (scavenging) and increase with vegetation dieback in winter (Opitz et al 2020). Moreover, Braskerud (2001) found that the effect of wetland vegetation on hydraulic efficiency was linked to seasonal vegetation development, increasing during the summer und decreasing during winter, with hydraulic efficiencies of 0.86 and 0.78, respectively.…”

“…In contrast to surface-flow wastewater treatment wetlands, mine water treatment wetlands usually display less performance fluctuation due to ecological or seasonal variability, with physico-chemical iron and TSS removal only moderately affected by environmental variations (Gu et al 2006;Hedin 2008). Rather, treatment efficiency is more often affected by stochastic fluctuations as well as distinct variations in consequence of inconsistent hydraulic loading or retention time (Opitz et al 2020;Stark et al 1994). The effect of environmental and especially gas transfer effects on passive system performance may be reduced by ensuring thorough aeration at the inlet of (and potentially between) ponds (Cravotta 2007(Cravotta , 2015Geroni et al 2012).…”

“…It was also noted at several sites that newly constructed wetlands require up to three vegetation cycles for full maturation, which was mostly attributed to progressive development and coverage of plant communities (Fennessy and Mitsch 1989;Stark et al 1988;Wildemann et al 1993), but likely also applies to bacterial communities (Samsó and García 2013). If regulatory standards must be met from day one, it may prove necessary to either oversize the system, as recommended by Wildemann et al (1993) or to (transitionally) install an additional sediment filter for effluent polishing, as successfully demonstrated by Opitz et al (2019Opitz et al ( , 2020.…”

“…A better understanding of macrophyte-related effects would go a long way towards circumscribing or parameterising the difference between settling ponds and wetlands and to ultimately improving the design and sizing of composite passive systems. Exemplary hydrochemical and environmental juxtaposition of settling ponds and wetlands in this study is provided from international literature and a closely monitored passive pilot plant featuring equally sized, consecutive settling ponds and wetlands, as described in Opitz et al (2019Opitz et al ( , 2020.…”

Optimising Operational Reliability and Performance in Aerobic Passive Mine Water Treatment: the Multistage Westfield Pilot Plant

“…Concentrations of metal(loid)s other than Fe or Mn are low despite considerable mobility in the surrounding mined land, which is attributable to the high sorption capacity of the electrostatic precipitator ashes (Mishra & Tripathi, 2008) and to the circumneutral character of the seepage water where solubility of most metals is low (Stumm & Morgan, 1996). Seepage water pumped to the conventional treatment plant is thoroughly oxygenated due to the temporary impoundment in drainage pond and RTR3, which is why Fe levels in the raw water are relatively low (Opitz et al, 2020). Temporal fluctuations in seepage water chemistry are attributable to the varying mixing ratio of seepage water, rainwater and surface runoff in drainage pond and RTR3 in consequence of the discontinuous pump operation.…”