A preliminary study to design a floating treatment wetland for remediating acid mine drainage-impacted water using vetiver grass (Chrysopogon zizanioides)

Abstract

Acid mine drainage (AMD) is extremely acidic, sulfate-rich effluent from abandoned or active mine sites that also contain elevated levels of heavy metals. Untreated AMD can contaminate surface and groundwater and pose severe ecological risk. Both active and passive methods have been developed for AMD treatment consisting of abiotic and biological techniques. Abiotic techniques are expensive and can create large amounts of secondary wastes. Passive biological treatment mainly consists of aerobic or anaerobic constructed wetlands. While aerobic wetlands are economical, they are not effective if the pH of the AMD is < 5. Anaerobic wetlands use organic-rich substrates to provide carbon source to iron- and sulfate-reducing bacteria. The efficiency of these systems declines overtime and requires continuous maintenance. Our objective is to develop an alternative, low-cost, and sustainable floating wetland treatment (FWT) system for AMD for the abandoned Tab-Simco coal mining site in Illinois using vetiver grass (Chrysopogon zizanioides). Tab-Simco AMD is highly acidic, with mean pH value of 2.64, and contains high levels of sulfate and metals. A greenhouse study was performed for a 30-day period in order to screen and optimize the necessary parameters to design a FWT system. Water quality and plant growth parameters were continuously monitored. Results show significant SO removal, resulting in increased pH, particularly at higher planting densities. Vetiver also helped in metal removal; high amounts of Fe, Zn, and Cu were removed, with relatively lower amounts of Pb, Al, and Ni. Iron plaque formation on the root was observed, which increased metal stabilization in root and lowered root to shoot metal translocation. Vetiver was tolerant of AMD, showing minimal change in biomass and plant growth. Results obtained are encouraging, and a large scale mesocosm study is now in progress, as the next step to develop the vetiver-based system for AMD treatment.

Phytoremediation Using Aquatic Plants

“…FTWs have been studied principally for their capacity to remove nutrients, but there have also been attempts to assess heavy metal, pathogen and phytoplankton removal (Borne, 2014;Yeh et al, 2015;Jones et al, 2017;Kiiskila et al, 2017). FTWs have been deployed at a variety of different scales including microcosms, mesocosms, and as pilot trials within lagoons (Headley and Tanner, 2008;Ladislas et al, 2013;Chang et al, 2014;McAndrew et al, 2016;Nichols et al, 2016;Kiiskila et al, 2017).…”

“…FTWs have been studied principally for their capacity to remove nutrients, but there have also been attempts to assess heavy metal, pathogen and phytoplankton removal (Borne, 2014;Yeh et al, 2015;Jones et al, 2017;Kiiskila et al, 2017). FTWs have been deployed at a variety of different scales including microcosms, mesocosms, and as pilot trials within lagoons (Headley and Tanner, 2008;Ladislas et al, 2013;Chang et al, 2014;McAndrew et al, 2016;Nichols et al, 2016;Kiiskila et al, 2017). Here the experimental polluted water used has included storm water, lake water, river water, sewage effluents, domestic wastewaters, refinery wastewater, acid mine drainage, and livestock effluents (Zhu et al, 2011;Li et al, 2012;Borne, 2014;Wang and Sample, 2014a;Abed, Almuktar and Scholz, 2017;Kiiskila et al, 2017).…”

“…FTWs have been deployed at a variety of different scales including microcosms, mesocosms, and as pilot trials within lagoons (Headley and Tanner, 2008;Ladislas et al, 2013;Chang et al, 2014;McAndrew et al, 2016;Nichols et al, 2016;Kiiskila et al, 2017). Here the experimental polluted water used has included storm water, lake water, river water, sewage effluents, domestic wastewaters, refinery wastewater, acid mine drainage, and livestock effluents (Zhu et al, 2011;Li et al, 2012;Borne, 2014;Wang and Sample, 2014a;Abed, Almuktar and Scholz, 2017;Kiiskila et al, 2017). Mesocosm-scale studies are the most prominent form of exploration into the effectiveness of FTW thus far , although there have been a few examples of deployment at field-scale, such as Zhao et al (2012)who demonstrated thatTN and TP concentrations could be reduced in a polluted Chinese river.…”

THE ABIOTIC STRESS RESPONSE OF HYDROPONIC VETIVER GRASS (Chrysopogon zizanioides L.) TO ACID MINE DRAINAGE AND ITS POTENTIAL FOR ENVIRONMENTAL REMEDIATION

“…For field purposes, these results have shown that handheld meters for DO and conductivity could serve for on-site monitoring of plant health and metal reduction, respectively. Common trends among metals were observed; from the largescale experiment, vetiver accumulated greater Fe (17,300 µg g -1 ), Al (3405 µg g -1 ), Mn (1080 µg g -1 ), Zn (113 µg g -1 ) and Cr (62.3 µg g -1 ), with lower Ni (41.2 µg g -1 ), Cu (24.6 µg g -1 ) and Pb (5.37 µg g -1 , [3][4][5] Fe, Al, and Mn. 4 Several plants have been screened for AMD tolerance, including Typha latifolia, Scirpus validus, and many others.…”

“…4,5 though little is known about tolerance mechanisms to this complex medium. Single factors like individual metals have been the focus of abiotic stress research; however, plants are exposed to multiple stresses under normal conditions.…”