A Modular Field-Bioreactor for Acid Rock Drainage Treatment

Abstract

The paper focuses on the improvements to engineered features of a passive technology that has been used for remediation of acid rock drainage (ARD). This passive remedial technology, a sulfate-reducing bacteria (SRB) bioreactor, takes advantage of the ability of SRB that, if supplied with a source of organic carbon, can increase pH and alkalinity of the water and immobilize metals by precipitating them as metal sulfides or hydroxides.The remoteness of ARD sites and their abundance require that the design of an SRB bioreactor be simple and inexpensive. Therefore, bioreactors need to be designed to a size that allows for transportation using primitive roads. To satisfy these requirements a design for a modular treatment system was developed using reactive cartridges (RC) that are prefabricated as 2.44-meter diameter vessels. The RC has been designed so it supports the prime functional aspects of a bioreactor such as high permeability, ample supply of organic carbon, ability to maintain anaerobic conditions, and capacity to accumulate precipitated metals and means for their periodical removal, as needed. In addition, the configuration of the RC allows for an easy replacement of the organic carbon. The RCs can be transported to an ARD site and assembled into a treatment system with a number of modules as required by the ARD flow rate and the metals load. A bioreactor system consisting of four RCs will be installed at an abandoned mine site with ARD of pH 5 or lower and a significant load of metals. The process of site selection is in progress.The RC design was developed by the Mine Waste Technology Program (MWTP) at MSE Technology Applications (MSE), Butte, Montana, USA.

Evaluation of a Two-Stage Passive Treatment Approach for Mining Influenced Waters

“…the substrate introduced by Zaluski et al (2006). The influent water (effluent from limestone reactors) was pumped from the bottom to the top of the biocolumn.…”

“…Passive bioreactor system promoting sulfate reducing bacterial activity can mitigate all three of these issues. However, the presence of Fe and Al in MIWs influent to passive bioreactor systems has historically cause problems with clogging by Fe and Al(OH) 3 precipitates (Zaluski et al 2006). Clogging of passive bioreactor systems can result in failure long before the organic substrate in the bioreactors has been depleted.…”

“…The lack of specifications for organic substrate and inorganic material fractions and physical, chemical and biological characteristics are an example. The system design by Ordonez et al used only undefined compost for organic substrate where as Blowes (2001), Wildeman (2001), and Zaluski et al (2006) recommend mixtures of organic substrates. There is a need for systematic physical, chemical and biological characterization of the organic substrates used in these passive bioreactor systems relative to SO 4 reducing activity and metal removal efficiency.…”

Substrate Degradation and Metal Removal Performance of a 1,500-Gallon Sulfate-Reducing Bioreactor for Mining-Influenced Water Treatment

“…Design and performance optimization have also been studied by Zaluski et al (2006). In addition, several bench-scale studies on substrate selection have been conducted , Place et al 2005, Seyler et al 2003, but much remains unknown about the performance of field-scale systems.…”

“…In this study, substrate degradation and metal removal capabilities of two identical 1,500-gallon bioreactors was examined over a 12-month period. The conceptual design of the bioreactors was presented in Zaluski et al (2006). To assess the extent of substrate degradation and sustainability, several parameters were analyzed: organic and inorganic carbon ratios, organic acids and starch contents, and cellulose and lignin fractions.…”