Assessing Alternative Supporting Organic Materials for the Enhancement of Water Reuse in Subsurface Constructed Wetlands Receiving Acid Mine Drainage

Abstract

Acid mine drainage (AMD) is a global problem with severe consequences for the environment. South Africa’s abandoned mines are a legacy from the country’s economic dependence on the mining sector, with consequent negative impacts on ecosystems. AMD remediation includes active and passive techniques. Constructed wetlands (a passive technique) have lower operational costs but require larger spaces and longer timeframes to achieve the remediation of AMD, and are supported by anaerobic sulphate-reducing bacteria (SRB), which capable of remediating high-sulphate-laden AMD while precipitating dissolved metals from the AMD. Organic substrates supporting these activities are often the limiting factor. When enhancing existing passive AMD remediation technologies, alternative waste material research that may support SRB activity is required to support the circular economy through the reduction in waste products. Chicken feathers show potential as a substrate enhancer, boosting organic carbon availability to SRB, which sustains passive AMD treatment processes by achieving pH elevation, sulphate and metal reductions in AMD water for reuse. Microbial biodiversity is essential to ensure the longevity of passive treatment systems, and chicken feathers are proven to have an association with SRB microbial taxa. However, the longer-term associations between the AMD water parameters, microbial diversity and the selected substrates remain to be further investigated.

Emerging Strategies for Mitigating Acid Mine Drainage Formation and Environmental Impacts: A Comprehensive Review of Recent Advances

“…Acid mine drainage (AMD) is an emerging environmental issue that is difficult to avoid in most mining activities (Oberholzer et al, 2022) . AMD is formed when sulfide minerals in the soil are exposed to a rich oxygen atmosphere so that they undergo an oxidation process and then react with water, air, and biotic components.…”

Propose the surface flow constructed wetland in the treatment of acid drainage in the closure of a tailings deposit

“…Regarding the efficiency of passive treatment with constructed Wetlands, it will depend on various factors such as the chemical composition of acid drainage, the degree of acidity, the accumulation of toxic metals and the organic material used [21]. Likewise, organic materials have been used for the treatment of DAM in constructed wetlands, such as cow dung, guano, eggshell, bamboo chips, among others [22].…”

“…According to Oberholzer, M., et al (2022) [22], the result of the pH levels in their wetland treatment system were the following: the pH was raised from 2.62 to 7.04 by implanting cow dung; Also, fly ash was used as a substrate, obtaining as a result a pH of 2.62 to 6.52.…”