Floating Garden For Acid Mine Drainage Treatment
A. Yusmur, I. Wahyuni, S. Bahri

Source: SEAMEO BIOTROP's Research Grant | 2020



Approximately more than 350 M m3 /year of water is produced globally each year as side effect coal extraction and natural processes in Kalimantan mining (Adaro, 2019). Huge volume of waste dump (approx 208 M BCM/year) where mine water is typically produced an acid pH with high heavy metal or sedimentation from waste dump where final void will be created after overburden backfilling. The high acidity in mine drainage causes the dissolution of heavy metals in the surrounding area (Palihakkara et al, 2018). Where coal is hosted in sulfide-bearing deposits, pyrite, and other sulfides in the tailings can oxidize, resulting in acid generation and pH decrease after deposition and must be treated in water treatment facilities.

Acid mine drainage (AMD) is a major environmental impact associated with the mining industry. Elevated acidic conditions resulting from the discharge of AMD into the surrounding environment can cause heavy metals to dissolve and transport through water streams and accumulate in the aquatic environment, posing a risk to the health of living organisms.

Most studies have focused on the role of vegetation in driving in situ rehabilitation and the establishment of a stable, self-sustaining ecosystem in Pit Lake. Microbial communities can make important contributions to key aspects of water rehabilitation including pH neutralization (Santini et al., 2015a, 2016). But it will take time where the water will accumulate in pit lake and must be drain to river. Water quality compliance standards: pH, TSS, Fe, Mn, Al and Discharge Water. The water treatment facilities in operation using usually use active treatment; Gravity and Coagulation Process, which it has to Daily and monthly monitoring at each compliance point and monthly reporting to government.

Consequently, there is a need for pit lake water quality improvement devices that are effective at removing the fine suspended particulate fraction of the mine water and the associated metal contaminants in order to minimize the impacts on downstream aquatic ecosystems. Floating garden is an in-situ passive treatment as an option. Floating garden is an ancient technology that applied around the world. Aztec ethnic in Mexico central of America (Crossley, 2004), India and Bangladesh (IUCN, 2005), Myanmar (Lwin & Sharma, 2012; Khurtsia, 2015), and ethnic of Banjar Amuntai in south Kalimantan, Indonesia used this technology for 200 years ago. It is a form of hydroponics or soil-less culture. Aquatic plants such as water hyacinth (Eichhornia crassipes) is used to construct floating platforms as buoyant mat and as organic matter and Typha sp as appropriate plants species that have an affinity for creating auto-buoyant mats. Organic matter and Typha can increase water quality (Yusmur et al, 2019). This application is also for acid reduction and metals removal, and suspended solids removal (Smith and Kalin (2000).

Principally, a floating treatment system harnesses interaction among plants, microorganisms, water, and the atmosphere to remove contaminants (Kramer 2005; Khandare et al. 2013). The combination of vegetation with the help of microbes makes an important contribution at this time to the main aspects of water rehabilitation including pH neutralization (Santini et al., 2015a, 2016, Ijaz et al. 2015; Ijaz et al. 2016; Rehman et al. 2018, 2019) (Figure 1). Removal of organic and inorganic pollutants through bacteria and plants synergism. Trace metals in floating garden system are removed through chemical processes performed by plants, bacteria, and/or algae that help entrap trace metals into the biofilms formed on roots.

The constructed garden treatment approach as Floating treatment wetlands (FTWs) in water treatment is a passive remediation option that are an innovative product of ecological engineering, has proven to be a cost effective and long-lasting solution in abating toxic pollutant concentrations (Rehman et al, 2019, Palihakkara et al, 2018). The present study assesses the feasibility of a floating treatment wetland application for abatement of Fe, Mn and Al concentrations in mine drainage. The applicability of floating garden treatment was examined using a microcosm study design. Several researchers have reported that this approach can be used to comprehensively understand the natural phenomenon under study. Eichhornia crassipes (water hyacinth), a common aquatic weed, was used as the phytoremediation media, as this plant has been found to bio accumulate heavy metals.


The efficiency of the floating garden concept depends on several parameters namely, design, selection of floating media, type of vegetation, climate suitability for plant growth, and the level of maintenance provided during the system run (De Stefani et al. 2011). Therefore this study aims to:

a. Create a floating garden planting media

b. Measuring water quality improvements from the floating garden system 3

c. Design and implement a floating garden for the management of acid mine drainage in the mine pond


The investigation reports from this research show the promising role on water hyacinth in enhancing the capability of plants to restore the quality of mine waste-water by reducing polluting factors through increasing pH level, and reducing Fe, Mn, Al, COD, BOD, respectively. Despite being performed at laboratory scale and for a short time period, the investigation reinforces the usefulness of water hyacinth as a means of restoring quality of waste water through the innovative mode of floating garden system. 

The hyperaccumulator plant, water hyacinth and Typha sp, proves to be an excellent choice for water remediation due to its survival in harsh conditions while being able to interact with microbial life and optimize its performance in decontaminating water. Furthermore, this report reveals the potential of floating garden for application in the field-scale as effective to provide plant and microbe interaction for removal of organic and inorganic pollutants, heavy metals, and other toxicity. While water hyacinth and Typha sp easy to find and become a problem in sub optimal land around the mining area, but they appropriate choice of pollutant-tolerant vegetation promises an ecological technology that can be retrofitted and custom designed for in-situ treatment of contaminated water virtually anywhere that plants can grow.

Bamboo rafts is one of the mat technologies that can be applied to the floating garden system for acid mine drainage passive treatment and other application in floating agriculture in post mining area. It is suggested to add manure to water hyacinth compost, for accelerating the decomposition proses of water hyacinth particles and to increase nutrients for the plants as phytoremediation plant and to support the productivity. 

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