Construction of a passive sulfate treatment system

Abstract

The paper reports on the third phase of constructing a passive sulfate reduction system with sulfur sequestering. The tiered approach included bench- and pilot-scale systems to prove the feasibility of using a passive treatment solution. This included the use of a biochemical reactor (BCR) with different proportions of wood chips, straw, manure, limestone, and biochar to culture sulfate-reducing bacteria. In addition, the concept of using a fixed-bed anaerobic bioreactor (FBAR), where alcohol was added to enhance the sulfate reducer activity, was also tested. In total, three BCRs and two FBARs were set up for this stage of the assessment. The resulting treated leachate was then passed through different media types to remove sulfur species generated by the bacteria, with an aerobic wetland used to polish the effluent. The success of the bench-scale (Tier 1) project led to a pilot-scale system (Tier 2) being constructed and monitored in spring 2020, the results of which confirmed the success of the bench-scale testing and provided useful insights into management of the system, particularly in winter months. The COVID crisis has had its impact, but the system has operated continuously and ran through 2021. This led to planning permission being awarded for the project, which enabled Tier 3 construction in late 2022/early 2023. © 2022 Australian Centre for Geomechanics, Perth.